Antivirals for influenza in healthy adults: systematic review

Neuraminidase inhibitors for treatment and prophylaxis of influenza in children: systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

To assess the effects of the neuraminidase inhibitors oseltamivir and zanamivir in treatment of children with seasonal influenza and prevention of transmission to children in households.

DESIGN

Systematic review and meta-analysis of data from published and unpublished randomised controlled trials.

DATA SOURCES

Medline and Embase to June 2009, trial registries, and manufacturers and authors of relevant studies. Review methods Eligible studies were randomised controlled trials of neuraminidase inhibitors in children aged </=12 in the community (that is, not admitted to hospital) with confirmed or clinically suspected influenza. Primary outcome measures were time to resolution of illness and incidence of influenza in children living in households with index cases of influenza.

RESULTS

We identified four randomised trials of treatment of influenza (two with oseltamivir, two with zanamivir) involving 1766 children (1243 with confirmed influenza, of whom 55-69% had influenza A), and three randomised trials for postexposure prophylaxis (one with oseltamivir, two with zanamivir) involving 863 children; none of these trials tested efficacy with the current pandemic strain. Treatment trials showed reductions in median time to resolution of symptoms or return to normal activities, or both, of 0.5-1.5 days, which were significant in only two trials. A 10 day course of postexposure prophylaxis with zanamivir or oseltamivir resulted in an 8% (95% confidence interval 5% to 12%) decrease in the incidence of symptomatic influenza. Based on only one trial, oseltamivir did not reduce asthma exacerbations or improve peak flow in children with asthma. Treatment was not associated with reduction in overall use of antibiotics (risk difference -0.30, -0.13 to 0.01). Zanamivir was well tolerated, but oseltamivir was associated with an increased risk of vomiting (0.05, 0.02 to 0.09, number needed to harm=20).

CONCLUSIONS

Neuraminidase inhibitors provide a small benefit by shortening the duration of illness in children with seasonal influenza and reducing household transmission. They have little effect on asthma exacerbations or the use of antibiotics. Their effects on the incidence of serious complications, and on the current A/H1N1 influenza strain remain to be determined.

Influenza virus resistance to antiviral agents: a plea for rational use

Although influenza vaccine can prevent influenza virus infection, the only therapeutic options to treat influenza virus infection are antiviral agents. At the current time, nearly all influenza A/H3N2 viruses and a percentage of influenza A/H1N1 viruses are adamantane resistant, which leaves only neuraminidase inhibitors available for treatment of infection with these viruses. In December 2008, the Centers for Disease Control and Prevention released new data demonstrating that a high percentage of circulating influenza A/H1N1 viruses are now resistant to oseltamivir. In addition, oseltamivir-resistant influenza B and A/H5N1 viruses have been identified. Thus, use of monotherapy for influenza virus infection is irrational and may contribute to mutational pressure for further selection of antiviral-resistant strains. History has demonstrated that monotherapy for influenza virus infection leads to resistance, resulting in the use of a new monotherapy agent followed by resistance to that new agent and thus resulting in a background of viruses resistant to both drugs. We argue that combination antiviral therapy, new guidelines for indications for treatment, point-of-care diagnostic testing, and a universal influenza vaccination recommendation are critical to protecting the population against influenza virus and to preserving the benefits of antiviral agents.

Seasonal influenza in adults and children--diagnosis, treatment, chemoprophylaxis, and institutional outbreak management: clinical practice guidelines of the Infectious Diseases Society of America

Guidelines for the treatment of persons with influenza virus infection were prepared by an Expert Panel of the Infectious Diseases Society of America. The evidence-based guidelines encompass diagnostic issues, treatment and chemoprophylaxis with antiviral medications, and issues related to institutional outbreak management for seasonal (interpandemic) influenza. They are intended for use by physicians in all medical specialties with direct patient care, because influenza virus infection is common in communities during influenza season and may be encountered by practitioners caring for a wide variety of patients.

School closure may be effective in reducing transmission of respiratory viruses in the community

Proposed measures to contain pandemic influenza include school closure, although the effectiveness of this has not been investigated. We examined the effect of a nationwide elementary school strike in Israel in 2000 on the incidence of influenza-like illness. In this historical observational study of 1.7 million members of a preferred provider organization, we analysed diagnoses from primary-care visits during the winter months in 1998-2002. We calculated the weekly ratio of influenza-like diagnoses to non-respiratory diagnoses, and fitted regression models for school-aged children, children's household members, and all other individuals aged >12 years. For each population the steepest drop in the ratio of influenza-like diagnoses to non-respiratory diagnoses occurred in the strike year 2 weeks after the start of the strike. The changes in the weekly ratio of influenza-like diagnoses to non-respiratory diagnoses were statistically significant (P=0.0074) for school children for the strike year compared to other years. A smaller decrease was also seen for the adults with no school-aged children in 1999 (P=0.037). The Chanukah holiday had a negative impact on the ratio for school-aged children in 1998, 1999 and 2001 (P=0.008, 0.006 and 0.045, respectively) and was statistically significant for both adult groups in 1999 and for adults with no school-aged children in 2001. School closure should be considered part of the containment strategy in an influenza pandemic.

Intranasal administration of alpha interferon reduces seasonal influenza A virus morbidity in ferrets

The type I interferon (IFN) response represents one of the first lines of defense against influenza virus infections. In this study, we assessed the protective potential of exogenous IFN-alpha against seasonal and highly pathogenic influenza viruses in ferrets. Intranasal treatment with IFN-alpha several hours before infection with the H1N1 influenza A virus strain A/USSR/90/77 reduced viral titers in nasal washes at least 100-fold compared to mock-treated controls. IFN-treated animals developed only mild and transient respiratory symptoms, and the characteristic fever peak seen in mock-treated ferrets 2 days after infection was not observed. Repeated application of IFN-alpha substantially increased the protective effect of the cytokine treatment. IFN-alpha did not increase survival after infection with the highly pathogenic H5N1 avian influenza A virus strain A/Vietnam/1203/2004. However, viral titers in nasal washes were significantly reduced at days 1 and 3 postinfection. Our study shows that intranasal application of IFN-alpha can protect ferrets from seasonal influenza viruses, which replicate mainly in the upper respiratory tract, but not from highly pathogenic influenza viruses, which also disseminate to the lung. Based on these results, a more intensive evaluation of IFN-alpha as an emergency drug against pandemic influenza A is warranted.

Threat of an influenza pandemic: family physicians in the front line

Background

The chance of an influenza pandemic is real and clinicians should keep themselves informed about the rationale and science behind preventive and therapeutic principles relating to an (impending) influenza pandemic.

Discussion

Vaccination is considered the best prevention in case of a pandemic threat and first choice to contain the impact of a pandemic. Pending the availability of an effective pandemic vaccine, antivirals are likely the only effective agents for prevention and treatment. When an influenza pandemic is impending, all interventions aim to prevent people becoming infected and to suppress replication and transmission of the virus as much as possible. Antivirals will be prescribed to patients with laboratory confirmed pre-pandemic influenza as well as to their contacts (post-exposure prophylaxis) which may delay development of or even prevent a pandemic. During a manifest influenza pandemic, however, there is large-scale spreading of the influenza virus. Therefore, preventive use of antivirals is less efficient to prevent transmission. Delaying the pandemic is then important in order to prevent exhausting public health resources and disruption of society. Thus, during a manifest pandemic everyone with influenza symptoms should receive antivirals as quickly as possible, regardless of virological confirmation. To ensure optimal effectiveness of antivirals and to minimize development of drug resistant viral strains, the use of antivirals for annual influenza should be restrictive. The crucial position of family physicians during an (impending) influenza pandemic necessitates the development of primary health care guidelines on this topic for all countries.

Summary

Family physicians will play a key role in assessing and treating victims of a new influenza virus, and in reassuring the worried well. We outline various possible interventions in the event of an impending and a manifest influenza pandemic, such as non-medial measures, prescription of antivirals, and vaccination, and emphasize the need for pandemic influenza preparedness.

Effect of a neuraminidase inhibitor (oseltamivir) on mouse jump-down behavior via stimulation of dopamine receptors

Oseltamivir (Tamiflu, Roche Laboratories, Inc.) is a neuraminidase inhibitor that can cause jumpdown behaviors in children. There is a mouse slip-down model, in which the dopamine D2 receptor activity is increased by serum sialoglycolipids and the mouse jump-down behavior appears in response to the dopamine D2 receptor agonist, PPHT. The present study examined the effect of oseltamivir on jump-down behavior in mice. Oseltamivir sialylates a serum glycolipid and this modified glycolipid induces jump-down behavior via the stimulation of dopamine D2 receptors. This mechanism may be involved in the abnormal behavior of children taking oseltamivir.

Use of rapid tests and antiviral medications for influenza among primary care providers in the United States

Limited data are available about how physicians diagnose and treat influenza. We conducted an internet-based survey of primary care and emergency physicians to evaluate the use of influenza testing and antiviral medications for diagnosis and treatment of influenza. In April 2005, an electronic link to a 33-question, web-based survey was emailed to members of the American College of Physicians, American Academy of Pediatrics, American Academy of Family Physicians, and American College of Emergency Physicians. Of the 157,674 physician members of the four medical societies, 2649 surveys were completed (1.7%). The majority of participants were internists (59%). Sixty percent of respondents reported using rapid tests to diagnose influenza. Factors associated with using rapid influenza tests included physician specialty, type of patient insurance, and practice setting. After controlling for insurance and community setting, emergency physicians and pediatricians were more likely to use rapid influenza tests than internists [odds ratio (OR) 3.7, confidence interval (CI): 2.3-6.1; and OR 1.7, CI: 1.4-2.1, respectively]. Eighty-six percent of respondents reported prescribing influenza antiviral medications. Reasons for not prescribing antivirals included: patients do not usually present for clinical care within 48 hours of symptom onset (53.0%), cost of antivirals (42.6%) and skepticism about antiviral drug effectiveness (21.7%). The use of rapid tests and antiviral medications for influenza varied by medical specialty. Educating physicians about the utility and limitations of rapid influenza tests and antivirals, and educating patients about seeking prompt medical care for influenza-like illness during influenza season could lead to more rapid diagnosis and improved management of influenza.

Estimating antiviral effectiveness against pandemic influenza using household data

Current estimates of antiviral effectiveness for influenza are based on the existing strains of the virus. Should a pandemic strain emerge, strain-specific estimates will be required as early as possible to ensure that antiviral stockpiles are used optimally and to compare the benefits of using antivirals as prophylaxis or to treat cases. We present a method to measure antiviral effectiveness using early pandemic data on household outbreak sizes, including households that are provided with antivirals for prophylaxis and those provided with antivirals for treatment only. We can assess whether antiviral drugs have a significant impact on susceptibility or on infectivity with the data from approximately 200 to 500 households with a primary case. Fewer households will suffice if the data can be collected before case numbers become high, and estimates are more precise if the study includes data from prophylaxed households and households where no antivirals are provided. Rates of asymptomatic infection and the level of transmissibility of the virus do not affect the accuracy of these estimates greatly, but the pattern of infectivity in the individual strongly influences the estimate of the effect of antivirals on infectivity. An accurate characterization of the infectiousness profile--informed by strain-specific data--is essential for measuring antiviral effectiveness.

Cochrane Review: Interventions for the interruption or reduction of the spread of respiratory viruses

BACKGROUND

Viral epidemics or pandemics such as of influenza or severe acute respiratory syndrome (SARS) pose a significant threat. Antiviral drugs and vaccination may not be adequate to prevent catastrophe in such an event.

OBJECTIVES

To systematically review the evidence of effectiveness of interventions to interrupt or reduce the spread of respiratory viruses (excluding vaccines and antiviral drugs, which have been previously reviewed).

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2006, issue 4); MEDLINE (1966 to November 2006); OLDMEDLINE (1950 to 1965); EMBASE (1990 to November 2006); and CINAHL (1982 to November 2006).

SELECTION CRITERIA

We scanned 2300 titles, excluded 2162 and retrieved the full papers of 138 trials, including 49 papers of 51 studies. The quality of three randomised controlled trials (RCTs) was poor; as were most cluster RCTs. The observational studies were of mixed quality. We were only able to meta-analyse case-control data. We searched for any interventions to prevent viral transmission of respiratory viruses (isolation, quarantine, social distancing, barriers, personal protection and hygiene). Study design included RCTs, cohort studies, case-control studies, cross-over studies, before-after, and time series studies.

DATA COLLECTION AND ANALYSIS

We scanned the titles, abstracts and full text articles using a standardised form to assess eligibility. RCTs were assessed according to randomisation method, allocation generation, concealment, blinding, and follow up. Non-RCTs were assessed for the presence of potential confounders and classified as low, medium, and high risk of bias.

MAIN RESULTS

The highest quality cluster RCTs suggest respiratory virus spread can be prevented by hygienic measures around younger children. Additional benefit from reduced transmission from children to other household members is broadly supported in results of other study designs, where the potential for confounding is greater. The six case-control studies suggested that implementing barriers to transmission, isolation, and hygienic measures are effective at containing respiratory virus epidemics. We found limited evidence that the more uncomfortable and expensive N95 masks were superior to simple surgical masks. The incremental effect of adding virucidals or antiseptics to normal handwashing to decrease respiratory disease remains uncertain. The lack of proper evaluation of global measures such as screening at entry ports and social distancing prevent firm conclusions about these measures.

AUTHORS' CONCLUSIONS

Many simple and probably low-cost interventions would be useful for reducing the transmission of epidemic respiratory viruses. Routine long-term implementation of some of the measures assessed might be difficult without the threat of a looming epidemic.

PLAIN LANGUAGE SUMMARY

Interventions to interrupt or reduce the spread of respiratory viruses Although respiratory viruses usually only cause minor disease, they can cause epidemics. Approximately 10% to 15% of people worldwide contract influenza annually, with attack rates as high as 50% during major epidemics. Global pandemic viral infections have been devastating because of their wide spread. In 2003 the severe acute respiratory syndrome (SARS) epidemic affected ˜8,000 people, killed 780, and caused an enormous social and economic crisis. A new avian influenza pandemic caused by the H5N1 strain might be more catastrophic. Single measures (particularly the use of vaccines or antiviral drugs) may be insufficient to interrupt the spread.We found 51 studies including randomised controlled trials (RCTs) and observational studies with a mixed risk of bias.Respiratory virus spread might be prevented by hygienic measures around younger children. These might also reduce transmission from children to other household members. Implementing barriers to transmission, isolation, and hygienic measures may be effective at containing respiratory virus epidemics. There was limited evidence that (more uncomfortable and expensive) N95 masks were superior to simple ones. Adding virucidals or antiseptics to normal handwashing is of uncertain benefit. There is insufficient evaluation of global measures such as screening at entry ports and social distancing.

A hospital-based strategy for setting priorities for antiviral prophylaxis during an influenza pandemic

An influenza pandemic would place an unprecedented strain on the nation's healthcare system-a compelling reason to carefully plan how priorities would be set for distributing antiviral medications. While antiviral medications have been added to the Strategic National Stockpile (SNS), these supplies are not designated as frontline resources and remain far from sufficient to provide mass prophylaxis for the entire population of the country. In the healthcare setting, providing general chemoprophylaxis may not be feasible because of high costs or inadequate supply. We propose a hospital-based strategy for setting priorities for antiviral prophylaxis that may offer a rational starting point for discussion and guide allocation decisions in the event of a shortage during a pandemic influenza outbreak.

Therapeutic activity of an anti-idiotypic antibody-derived killer peptide against influenza A virus experimental infection

The in vitro and in vivo activities of a killer decapeptide (KP) against influenza A virus is described, and the mechanisms of action are suggested. KP represents the functional internal image of a yeast killer toxin that proved to exert antimicrobial and anti-human immunodeficiency virus type 1 (HIV-1) activities. Treatment with KP demonstrated a significant inhibitory activity on the replication of two strains of influenza A virus in different cell lines, as evaluated by hemagglutination, hemadsorption, and plaque assays. The complete inhibition of virus particle production and a marked reduction of the synthesis of viral proteins (membrane protein and hemagglutinin, in particular) were observed at a KP concentration of 4 microg/ml. Moreover, KP administered intraperitoneally at a dose of 100 microg/mice once a day for 10 days to influenza A/NWS/33 (H1N1) virus-infected mice improved the survival of the animals by 40% and significantly decreased the viral titers in their lungs. Overall, KP appears to be the first anti-idiotypic antibody-derived peptide that displays inhibitory activity and that has a potential therapeutic effect against pathogenic microorganisms, HIV-1, and influenza A virus by different mechanisms of action.

Pandemic planning: non-pharmaceutical interventions

Ongoing concerns about the emergence of an influenza pandemic continue as the number of avian and human infections with the H5N1 virus mount. Adequate amounts of vaccine or anti-virals are unlikely to be available early on in a pandemic, and the latter could become ineffective because of resistance. These factors have focused attention on the use of non-pharmaceutical public health interventions to inhibit human-to-human transmission.

Influenza infection and COPD

Influenza is a disease with global impact that causes enormous morbidity and mortality on an annual basis. It primarily infects the respiratory tract and causes a broad range of illness ranging from symptomless infection to fulminant primary viral and secondary bacterial pneumonia. The severity of infection depends on both the virus strain and a number of host factors, primarily age and the presence of comorbid conditions such as cardiopulmonary disease. The mortality and utilization of healthcare resources associated with influenza is concentrated in the elderly and those with coexisting disease such as chronic obstructive pulmonary disease (COPD). Increasing use of vaccination and the development of new antiviral drugs hold out hope that the burden of disease associated with influenza can be reduced. However the constant emergence of new influenza strains and the current risk of avian influenza pandemic serve as warnings that influenza will remain a serious pathogen for the foreseeable future.

Preparing for an Influenza Pandemic in Singapore

The national strategy against pandemic influenza essentially consists of 3 prongs: (i) effective surveillance, (ii) mitigation of the pandemic’s impact, and (iii) render the population immune through vaccination. When the pandemic hits Singapore, the response plan aims to achieve the following 3 outcomes: (i) maintenance of essential services to limit social and economic disruption, (ii) reduction of morbidity and mortality through antiviral treatment, and (iii) slow and limit the spread of influenza to reduce the surge on healthcare services. The biggest challenge will come from managing the surge of demand on healthcare services. A high level of preparedness will help healthcare services better cope with the surge. Key words: Essential services, Healthcare, National preparedness, Non-pharmaceutical measures

A novel method for distinguishing between dsDNA and ssRNA virus infections

BACKGROUND

To commence proper antiviral treatment, timely knowledge of whether the infection is caused by DNA or RNA virus would be beneficial for the clinician.

OBJECTIVES

Our objective was to develop a method for distinguishing between DNA and RNA virus infections.

STUDY DESIGN

In this prospective study, total and differential count of leukocytes, serum C-reactive protein level, erythrocyte sedimentation rate, and quantitative flow cytometric analysis of FcgammaRI (CD64) on neutrophils and monocytes were obtained from 289 hospitalized febrile patients. After microbiological confirmation, 89 patients (31%) were found to have either bacterial (n=46) or viral (n=43) infection. The patient data was compared to 60 healthy controls.

RESULTS

For the first time ever, it was noticed that in dsDNA virus infections (n=21) the average amount of CD64 on neutrophils was over five-fold compared to ssRNA virus infections (n=22).

CONCLUSIONS

DNA virus score (DNAVS) point, which incorporates quantitative analysis of CD64 on neutrophils and total and differential count of leukocytes, varied between 0 and 8, and displayed 95% sensitivity and 100% specificity in distinguishing between dsDNA and ssRNA virus infections [average (S.D.); DNAVS points: 5.4 (2.5) vs. 0.3 (0.4); p<0.001].

Emergence of drug resistance: implications for antiviral control of pandemic influenza

Given the danger of an unprecedented spread of the highly pathogenic avian influenza strain H5N1 in humans, and great challenges to the development of an effective influenza vaccine, antiviral drugs will probably play a pivotal role in combating a novel pandemic strain. A critical limitation to the use of these drugs is the evolution of highly transmissible drug-resistant viral mutants. Here, we develop a mathematical model to evaluate the potential impact of an antiviral treatment strategy on the emergence of drug resistance and containment of a pandemic. The results show that elimination of the wild-type strain depends crucially on both the early onset of treatment in indexed cases and population-level treatment. Given the probable delay of 0.5-1 day in seeking healthcare and therefore initiating therapy, the findings indicate that a single strategy of antiviral treatment will be unsuccessful at controlling the spread of disease if the reproduction number of the wild-type strain (R0s) exceeds 1.4. We demonstrate the possible occurrence of a self-sustaining epidemic of resistant strain, in terms of its transmission fitness relative to the wild-type, and the reproduction number R0s. Considering reproduction numbers estimated for the past three pandemics, the findings suggest that an uncontrollable pandemic is likely to occur if resistant viruses with relative transmission fitness above 0.4 emerge. While an antiviral strategy is crucial for containing a pandemic, its effectiveness depends critically on timely and strategic use of drugs.

Sensitivity of H5N1 influenza viruses to oseltamivir: an update

Continued worldwide circulation of highly pathogenic influenza A (H5N1) viruses has raised concerns that they might adapt to humans and cause a pandemic. Preparedness plans rely on influenza vaccines and on the prophylactic and therapeutic use of neuraminidase inhibitors, especially the orally available drug oseltamivir. Although the efficacy of oseltamivir is well established for uncomplicated seasonal influenza, questions remain about its clinical effectiveness for human H5N1 infections. In this review, available data on the sensitivity of H5N1 viruses to oseltamivir in vitro, in animal models and in human patients are discussed. The factors that might limit the efficacy of oseltamivir treatment for human H5N1 infections are also discussed, in addition to options for improving treatment efficacy and limiting the development of drug resistance.

Self-interest versus group-interest in antiviral control

Antiviral agents have been hailed to hold considerable promise for the treatment and prevention of emerging viral diseases like H5N1 avian influenza and SARS. However, antiviral drugs are not completely harmless, and the conditions under which individuals are willing to participate in a large-scale antiviral drug treatment program are as yet unknown. We provide population dynamical and game theoretical analyses of large-scale prophylactic antiviral treatment programs. Throughout we compare the antiviral control strategy that is optimal from the public health perspective with the control strategy that would evolve if individuals make their own, rational decisions. To this end we investigate the conditions under which a large-scale antiviral control program can prevent an epidemic, and we analyze at what point in an unfolding epidemic the risk of infection starts to outweigh the cost of antiviral treatment. This enables investigation of how the optimal control strategy is moulded by the efficacy of antiviral drugs, the risk of mortality by antiviral prophylaxis, and the transmissibility of the pathogen. Our analyses show that there can be a strong incentive for an individual to take less antiviral drugs than is optimal from the public health perspective. In particular, when public health asks for early and aggressive control to prevent or curb an emerging pathogen, for the individual antiviral drug treatment is attractive only when the risk of infection has become non-negligible. It is even possible that from a public health perspective a situation in which everybody takes antiviral drugs is optimal, while the process of individual choice leads to a situation where nobody is willing to take antiviral drugs.

Current and future antiviral therapy of severe seasonal and avian influenza

The currently circulating H3N2 and H1N1 subtypes of influenza A virus cause a transient, febrile upper respiratory illness in most adults and children (“seasonal influenza”), but infants, the elderly, immunodeficient and chronically ill persons may develop life-threatening primary viral pneumonia or complications such as bacterial pneumonia. By contrast, avian influenza viruses such as the H5N1 virus that recently emerged in Southeast Asia can cause severe disease when transferred from domestic poultry to previously healthy people (“avian influenza”). Most H5N1 patients present with fever, cough and shortness of breath that progress rapidly to adult respiratory distress syndrome. In seasonal influenza, viral replication remains confined to the respiratory tract, but limited studies indicate that H5N1 infections are characterized by systemic viral dissemination, high cytokine levels and multiorgan failure. Gastrointestinal infection and encephalitis also occur. The licensed anti-influenza drugs (the M2 ion channel blockers, amantadine and rimantadine, and the neuraminidase inhibitors, oseltamivir and zanamivir) are beneficial for uncomplicated seasonal influenza, but appropriate dosing regimens for severe seasonal or H5N1 viral infections have not been defined. Treatment options may be limited by the rapid emergence of drug-resistant viruses. Ribavirin has also been used to a limited extent to treat influenza. This article reviews licensed drugs and treatments under development, including high-dose oseltamivir; parenterally administered neuraminidase inhibitors, peramivir and zanamivir; dimeric forms of zanamivir; the RNA polymerase inhibitor T-705; a ribavirin prodrug, viramidine; polyvalent and monoclonal antibodies; and combination therapies.

Effectiveness of oseltamivir treatment among children with influenza A or B virus infections during four successive winters in Niigata City, Japan

Oseltamivir has been used for treatment of influenza A and B infections, but recent reports documented that it was less active against the latter. We compared the effectiveness of oseltamivir in children between laboratory confirmed influenza A and B over 4 influenza seasons from 2001 to 2005 in a pediatric clinic in Japan. Among 1,848 patients screened, 299 influenza A and 209 influenza B patients were administered oseltamivir (treated groups), and 28 influenza A and 66 influenza B patients were assigned as non-treated groups. The duration of fever, defined as period when patients had the maximum temperature higher than 37.5 degrees C in three-time measurements in a day after the clinic visit, was evaluated among the four groups. In uni-variate analysis, the duration of fever was shorter for treated group than non-treated for influenza A (1.8 +/- 0.9 days vs 2.6 +/- 1.3 days, p < 0.01), but it was not significant for influenza B (2.4 +/- 1.3 days vs 2.8 +/- 1.2 days, p = 0.9). The fever duration was longer in treated influenza B than A patients (p < 0.01). Multi-variate analysis indicated younger age (< 6 years old) and higher body temperature at the clinic visit prolonged the duration of fever. Adjusted average duration of fever indicated that oseltamivir was effective for both types, but more effective on influenza A, and the benefit increased for younger children. Our data provide evidence that oseltamivir is beneficial for influenza infections, but the effectiveness is differed by type and age.

Oseltamivir and the risk of influenza-related complications and hospitalizations in patients with diabetes

OBJECTIVE

This subgroup analysis of a retrospective cohort study examined, from a managed care perspective, the risk of influenza-related complications and hospitalizations in patients with diabetes who were prescribed oseltamivir for the treatment of influenza and those who were not prescribed antiviral treatment.

METHODS

Health insurance claims data from the Thomson Healthcare MarketScan Research Database for 6 influenza seasons (October 1-March 31) between 2000 and 2006 were used to identify patients aged >/=18 years with influenza and diabetes. Patients who received a prescription for oseltamivir within 1 day of a diagnosis of influenza were compared with those who received no antiviral treatment. Outcomes included the frequency of pneumonia, respiratory diagnoses, and otitis media and its complications, and rates of hospitalization within 14 days of the diagnosis of influenza. Cox proportional hazards regression was used to determine the relative risk (RR) of influenza-related complications and hospitalizations.

RESULTS

A total of 9090 patients with diabetes and a diagnosis of influenza were identified who met all study criteria. Of these, 2919 (32%) received a prescription for oseltamivir and 6171 (68%) received no antiviral treatment. Patients receiving oseltamivir had a significant 17% reduction in the risk of respiratory illnesses (RR = 0.83; 95% CI, 0.73-0.93) and a 30% reduction in the risk of hospitalization for any reason (RR = 0.70; 95% CI, 0.52-0.94). There were no significant differences between the oseltamivir and control groups in terms of the risks for pneumonia (RR = 0.87; 95% CI, 0.64-1.18), otitis media and its complications (RR = 0.96; 95% CI, 0.48-1.91), or hospitalization for pneumonia (RR = 0.81; 95% CI, 0.41-1.58).

CONCLUSION

In this retrospective study, the risk of influenza-associated respiratory illnesses and the number of hospitalizations for any reason were reduced in patients with diabetes who were prescribed oseltamivir compared with an unmatched group that was not prescribed antiviral therapy.

Injectable peramivir mitigates disease and promotes survival in ferrets and mice infected with the highly virulent influenza virus, A/Vietnam/1203/04 (H5N1)

The post-exposure therapeutic efficacy of injectable peramivir against highly pathogenic avian influenza type A H5N1 was evaluated in mice and in ferrets. Seventy to eighty percent of the H5N1-infected peramivir-treated mice, and 70% in the oseltamivir treated mice survived the 15-day study period, as compared to 36% in control (vehicle) group. Ferrets were infected intranasally with H5N1 followed by treatment with multiple doses of peramivir. In two of three trials, a statistically significant increase in survival over a 16-18 day period resulted from peramivir treatment, with improved survival of 40-64% in comparison to mock-treated or untreated animals. Injected peramivir mitigates virus-induced disease, reduces infectious virus titers in the lungs and brains and promotes survival in ferrets infected intranasally with this highly neurovirulent isolate. A single intramuscular peramivir injection protected mice against severe disease outcomes following infection with highly pathogenic avian influenza and multi-dose treatment was efficacious in ferrets.

Amantadine and rimantadine for influenza A in children and the elderly

BACKGROUND

Although amantadine (AMT) and rimantadine (RMT) are used to relieve or treat influenza A symptoms in healthy adults, little is known about the effectiveness and safety of these antivirals in preventing and treating influenza A in children and the elderly.

OBJECTIVES

The aim of this review was to systematically consider evidence on the effectiveness and safety of AMT and RMT in preventing and treating influenza A in children and the elderly.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2007, issue 3); MEDLINE (1966 to July 2007) and EMBASE (1980 to July 2007).

SELECTION CRITERIA

Randomised or quasi-randomised trials comparing AMT and/or RMT in children and the elderly with placebo, control, other antivirals or comparing different doses or schedules of AMT and/or RMT or no intervention.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion and assessed methodological quality. Disagreements were resolved by consensus. In all comparisons except for one, the trials in children and in the elderly were analysed separately. Data were analysed and reported using Cochrane Review Manager 4.2. software.

MAIN RESULTS

In children, RMT was effective in the abatement of fever on day three of treatment. AMT showed a prophylactic effect against influenza A infection. AMT and RMT were not related to an increase in the occurrence of adverse effects. RMT also was considered to be well tolerated by the elderly, but showed no prophylactic effect. Different doses were comparable in the prophylaxis of influenza in the elderly, as well as in reporting adverse effects. Zanamivir prevented influenza A more effectively than RMT in the elderly.

AUTHORS' CONCLUSIONS

AMT was effective in the prophylaxis of influenza A in children. As confounding matters might have affected our findings, caution should be taken when considering which patients should to be given this prophylactic. Our conclusions about effectiveness of both antivirals for the treatment of influenza A in children were limited to a proven benefit of RMT in the abatement of fever on day three of treatment. Due to the small number of available studies we could not reach a definitive conclusion on the safety of AMT or the effectiveness of RMT in preventing influenza in children and the elderly.

Physical interventions to interrupt or reduce the spread of respiratory viruses: systematic review

OBJECTIVE

To systematically review evidence for the effectiveness of physical interventions to interrupt or reduce the spread of respiratory viruses.

DATA EXTRACTION

Search strategy of the Cochrane Library, Medline, OldMedline, Embase, and CINAHL, without language restriction, for any intervention to prevent transmission of respiratory viruses (isolation, quarantine, social distancing, barriers, personal protection, and hygiene). Study designs were randomised trials, cohort studies, case-control studies, and controlled before and after studies.

DATA SYNTHESIS

Of 2300 titles scanned 138 full papers were retrieved, including 49 papers of 51 studies. Study quality was poor for the three randomised controlled trials and most of the cluster randomised controlled trials; the observational studies were of mixed quality. Heterogeneity precluded meta-analysis of most data except that from six case-control studies. The highest quality cluster randomised trials suggest that the spread of respiratory viruses into the community can be prevented by intervening with hygienic measures aimed at younger children. Meta-analysis of six case-control studies suggests that physical measures are highly effective in preventing the spread of SARS: handwashing more than 10 times daily (odds ratio 0.45, 95% confidence interval 0.36 to 0.57; number needed to treat=4, 95% confidence interval 3.65 to 5.52); wearing masks (0.32, 0.25 to 0.40; NNT=6, 4.54 to 8.03); wearing N95 masks (0.09, 0.03 to 0.30; NNT=3, 2.37 to 4.06); wearing gloves (0.43, 0.29 to 0.65; NNT=5, 4.15 to 15.41); wearing gowns (0.23, 0.14 to 0.37; NNT=5, 3.37 to 7.12); and handwashing, masks, gloves, and gowns combined (0.09, 0.02 to 0.35; NNT=3, 2.66 to 4.97). The incremental effect of adding virucidals or antiseptics to normal handwashing to decrease the spread of respiratory disease remains uncertain. The lack of proper evaluation of global measures such as screening at entry ports and social distancing prevent firm conclusions being drawn.

CONCLUSION

Routine long term implementation of some physical measures to interrupt or reduce the spread of respiratory viruses might be difficult but many simple and low cost interventions could be useful in reducing the spread.

Effects of a nutrient mixture on infectious properties of the highly pathogenic strain of avian influenza virus A/H5N1

Numerous outbreaks of avian influenza virus infection (A/H5N1) have occurred recently, infecting domestic birds, chicken and ducks. The possibility of the emergence of a new strain of influenza virus capable of causing a pandemic in humans is high and no vaccine effective against such a strain currently exists. A unique nutrient mixture (NM), containing lysine, proline, ascorbic acid, green tea extract, N-acetyl cysteine, selenium among other micro nutrients, has been shown to exert a wide range of biochemical and pharmacological effects, including an inhibitory effect on replication of influenza virus and HIV. This prompted us to investigate the potential anti-viral activity of a nutrient mixture (NM) and its components on avian influenza virus A/H5N1at viral dosages of 1.0, 0.1 and 0.01 TCID(50). Antiviral activity was studied in cultured cell lines PK, BHK-21, and Vero-E6. Virus lysing activity was determined by co-incubation of virus A/H5N1 with NM for 0-60 min, followed residual virulence titration in cultured SPEV or BHK-21 cells. NM demonstrated high antiviral activity evident even at prolonged periods after infection. NM antiviral properties were comparable to those of conventional drugs (amantadine and oseltamivir); however, NM had the advantage of affecting viral replication at the late stages of the infection process.

Limitations of current prophylaxis against influenza virus infection

Avian influenza has been a source of worldwide concern since Hong Kong authorities detected the first outbreak in 1997. Mainly as a result of poultry-to-human transmission, more than 200 cases of infection in humans have been attributed to the A/H5, A/H7, and A/H9 viral subtypes, with a case fatality rate for A/H5N1 infections exceeding 50%. A mutant or reassortant virus capable of efficient human-to-human transmission can set off a pandemic. Increased attention to prophylaxis against viral infection has identified several potentially complementary approaches: nonpharmacologic measures (eg, travel restrictions), vaccination, chemotherapeutic agents, and herbal/natural products. All have significant limitations that point out the need for additional modalities. Herbal/natural products, particularly those based on green tea extract, offer promise as adjuncts or alternatives to current interventions and warrant further evaluation in well-controlled human trials.

Interventions for the interruption or reduction of the spread of respiratory viruses

BACKGROUND

Viral epidemics or pandemics such as of influenza or severe acute respiratory syndrome (SARS) pose a significant threat. Antiviral drugs and vaccination may not be adequate to prevent catastrophe in such an event.

OBJECTIVES

To systematically review the evidence of effectiveness of interventions to interrupt or reduce the spread of respiratory viruses (excluding vaccines and antiviral drugs, which have been previously reviewed).

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2006, Issue 4); MEDLINE (1966 to November 2006); OLDMEDLINE (1950 to 1965); EMBASE (1990 to November 2006); and CINAHL (1982 to November 2006).

SELECTION CRITERIA

We scanned 2300 titles, excluded 2162 and retrieved the full papers of 138 trials, including 49 papers of 51 studies. The quality of three randomised controlled trials (RCTs) was poor; as were most cluster RCTs. The observational studies were of mixed quality. We were only able to meta-analyse case-control data. We searched for any interventions to prevent viral transmission of respiratory viruses (isolation, quarantine, social distancing, barriers, personal protection and hygiene). Study design included RCTs, cohort studies, case-control studies, cross-over studies, before-after, and time series studies.

DATA COLLECTION AND ANALYSIS

We scanned the titles, abstracts and full text articles using a standardised form to assess eligibility. RCTs were assessed according to randomisation method, allocation generation, concealment, blinding, and follow up. Non-RCTs were assessed for the presence of potential confounders and classified as low, medium, and high risk of bias.

MAIN RESULTS

The highest quality cluster RCTs suggest respiratory virus spread can be prevented by hygienic measures around younger children. Additional benefit from reduced transmission from children to other household members is broadly supported in results of other study designs, where the potential for confounding is greater. The six case-control studies suggested that implementing barriers to transmission, isolation, and hygienic measures are effective at containing respiratory virus epidemics. We found limited evidence that the more uncomfortable and expensive N95 masks were superior to simple surgical masks. The incremental effect of adding virucidals or antiseptics to normal handwashing to decrease respiratory disease remains uncertain. The lack of proper evaluation of global measures such as screening at entry ports and social distancing prevent firm conclusions about these measures.

AUTHORS' CONCLUSIONS

Many simple and probably low-cost interventions would be useful for reducing the transmission of epidemic respiratory viruses. Routine long-term implementation of some of the measures assessed might be difficult without the threat of a looming epidemic.

Prevention of infectious diseases in athletes

The sports medicine physician may face challenging issues regarding infectious diseases when dealing with teams or highly competitive athletes who have difficulties taking time off to recover. One must treat the individual sick athlete and take the necessary precautions to contain the spread of communicable disease to the surrounding team, staff, relatives, and other contacts. This article reviews preventive strategies for infectious disease in athletes, including immunization recommendations and prophylaxis guidelines, improvements in personal hygiene and prevention of spread of infectious organisms by direct contact, insect-borne disease precautions, and prevention of sexually transmitted diseases. A special emphasis on immunizations focuses on pertussis, influenza, and meningococcal prophylaxis.

The role of health care workers and antiviral drugs in the control of pandemic influenza

Until a vaccine against the new strain becomes available, the response to newly emerged pandemic influenza will consist of the use of antiviral drugs and measures that limit exposure to infectious individuals. These first-line defence measures include isolating cases upon diagnosis, reducing close contacts, the use of personal protective equipment and hygiene, and using antiviral drugs for treatment and prophylaxis. There are significant 'costs' associated with control measures, so to justify such interventions it is important to assess their potential to reduce transmission. In this paper, we determine the effect that a number of different antiviral interventions have on the reproduction number of infectives and the probability that an imported infection fades out, and determine parameter scenarios for which these interventions are able to eliminate an emerging pandemic of influenza. We also assess the role that health care workers play in transmission and the extent to which providing them with antiviral prophylaxis and personal protective equipment modifies this role. Our results indicate that this class requires protection to avoid a greatly disproportionate contribution to early infective numbers, and for the maintenance of a stable health care system. Further, we show that the role children play in increasing transmission is moderate, in spite of closer mixing with other children.

[Respiratory viruses: old and new. Review of diagnostic methods]

Acute respiratory infections (ARI) of viral origin are one of the main causes of morbidity and mortality worldwide. In addition to traditional viruses, such as the influenza virus, respiratory syncytial virus, rhinovirus, parainfluenza viruses 1 to 4, and adenovirus, other viruses such as metapneumovirus, new coronaviruses (human coronavirus NL63 and HKU1 and severe acute respiratory syndrome [SARS]-coronavirus), and recently bocaviruses, have been identified as causal agents of ARI. Although most of these viral infections follow a benign and selflimiting course in healthy adults, the consequences for the health care systems increase when they involve children, the elderly, immunosuppressed individuals, or those with chronic underlying diseases. These viral infections are an important cause of hospitalization and death, mainly during the cold months of the year, and, from a social-health perspective, ARI are a drain on economic resources and a frequent cause of work absenteeism. Occasionally, some of these viruses may cause emergent world health problems, as has occurred with the influenza virus pandemic strain and SARScoronavirus. While classical diagnostic methods based on culture and antigen detection remain useful for traditional respiratory viruses, recently described viruses are diagnosed mainly by molecular amplification techniques.

Development and validation of a liquid chromatographic-tandem mass spectrometric method for determination of oseltamivir and its metabolite oseltamivir carboxylate in plasma, saliva and urine

A bioanalytical method for the analysis of oseltamivir (OP) and its metabolite oseltamivir carboxylate (OC) in human plasma, saliva and urine using off-line solid-phase extraction and liquid chromatography coupled to positive tandem mass spectroscopy has been developed and validated. OP and OC were analysed on a ZIC-HILIC column (50 mm x 2.1 mm) using a mobile phase gradient containing acetonitrile-ammonium acetate buffer (pH 3.5; 10mM) at a flow rate of 500 microL/min. The method was validated according to published FDA guidelines and showed excellent performance. The lower limit of quantification for OP was determined to be 1, 1 and 5 ng/mL for plasma, saliva and urine, respectively and for OC was 10, 10 and 30 ng/mL for plasma, saliva and urine, respectively. The upper limit of quantification for OP was determined to be 600, 300 and 1500 ng/mL for plasma, saliva and urine, respectively and for OC was 10,000, 10,000 and 30,000 ng/mL for plasma, saliva and urine, respectively. The within-day and between-day precisions expressed as R.S.D., were lower than 5% at all tested concentrations for all matrices and below 12% at the lower limit of quantification. Validation of over-curve samples ensured that it would be possible with dilution if samples went outside the calibration range. Matrix effects were thoroughly evaluated both graphically and quantitatively. No matrix effects were detected for OP or OC in plasma or saliva. Residues from the urine matrix (most likely salts) caused some ion suppression for both OP and its deuterated internal standard but had no effect on OC or its deuterated internal standard. The suppression did not affect the quantification of OP.

The impact of prophylaxis of healthcare workers on influenza pandemic burden

Several models have rationalized the use of antiviral drugs as an early control measure for delaying the progression and limiting the size of outbreaks during an influenza pandemic. However, the strategy for use of these drugs is still under debate. We evaluated the impact of prophylaxis of healthcare workers (HCWs) through a mathematical model that considers attack rates in a range of 25-35% in the general population and 25-50% among HCWs. Simulations and uncertainty analysis using the demographics of the province of Ontario, Canada show that increasing prophylaxis coverage of HCWs has little impact on reducing the reproduction number of disease transmission and may not prevent the occurrence of an outbreak if expected. However, it does enable a high level of treatment, which substantially reduces morbidity and mortality in the population as a whole. Therefore, prophylaxis of HCWs should be considered an important part of public health efforts for minimizing influenza pandemic burden and its socio-economic disruption.

How Much Would Closing Schools Reduce Transmission During an Influenza Pandemic?

BACKGROUND

When deciding whether to close schools during an influenza pandemic, authorities must weigh the likely benefits against the expected social disruption. Although schools have been closed to slow the spread of influenza, there is limited evidence as to the impact on transmission of disease.

METHODS

To assess the benefits of closing schools for various pandemic scenarios, we used a stochastic mathematical model of disease transmission fitted to attack rates from past influenza pandemics. We compared these benefits with those achieved by other interventions targeted at children.

RESULTS

Closing schools can reduce transmission among children considerably, but has only a moderate impact on average transmission rates among all individuals (both adults and children) under most scenarios. Much of the benefit of closing schools can be achieved if schools are closed by the time that 2% of children are infected; if the intervention is delayed until 20% of children are infected, there is little benefit. Immunization of all school children provides only a slight improvement over closing schools, indicating that schools are an important venue for transmission between children. Relative attack rates in adults and children provide a good indication of the likely benefit of closing schools, with the greatest impact seen for infections with high attack rates in children.

CONCLUSIONS

Closing schools is effective at reducing transmission between children but has only a moderate effect on average transmission rates in the wider population unless children are disproportionately affected.

[Antiviral therapy: from influenza to Pfeiffer's disease]

Antiviral drug therapy has rapidly evolved in recent years. A large number of specific inhibitors against newly detected viral targets has been developed. Viral infections except HIV and viral hepatitis infections are clinically relevant mostly in severely immunocompromised patients. Especially respiratory viral infections and herpes virus infections are associated with high morbidity and mortality in these patients. Therapeutic and preventive strategies have been developed for a number of these infections. There is high priority for the development of new substances for a number of viruses not yet treatable and substances active against resistant viral strains.

A delay differential model for pandemic influenza with antiviral treatment

The use of antiviral drugs has been recognized as the primary public health strategy for mitigating the severity of a new influenza pandemic strain. However, the success of this strategy requires the prompt onset of therapy within 48 hours of the appearance of clinical symptoms. This requirement may be captured by a compartmental model that monitors the density of infected individuals in terms of the time elapsed since the onset of symptoms. We show that such a model can be expressed by a system of delay differential equations with both discrete and distributed delays. The model is analyzed to derive the criterion for disease control based on two critical factors: (i) the profile of treatment rate; and (ii) the level of treatment as a function of time lag in commencing therapy. Numerical results are also obtained to illustrate the feasible region of disease control. Our findings show that due to uncertainty in the attack rate of a pandemic strain, initiating therapy immediately upon diagnosis can significantly increase the likelihood of disease control and substantially reduce the required community-level of treatment. This suggests that reliable diagnostic methods for influenza cases should be rapidly implemented within an antiviral treatment strategy.

Sodium cromoglicate: an ineffective drug or meta-analysis misused?

Sodium cromoglicate (SCG) has been available since around 1970 for the treatment of asthma and other allergic disorders in both adults and children. It has been approved for use around the world. Over the period of its development, a number of different formulations were introduced. In 1999, a systematic review of SCG use in childhood asthma was carried out and reported initially as a poster. Further systematic reviews and papers followed from the same authors and finally a Cochrane Collaboration review was published in 2003. All concluded that SCG was ineffective in paediatric asthma. Both the British Thoracic Society Guidelines for the treatment of paediatric asthma and the Model List of Essential Drugs of the WHO now reflect these conclusions. This paper looks carefully at the conclusions of these systematic reviews and raises concerns about the interpretation of the results. These failed to take adequate account of the changes with time in both the formulations used and the age groups examined, and also failed to take adequate note of the totality of information available over all end-points. One primary end-point was based on only four out of the 24 studies included in the review. Rather than having no effect, it is demonstrated that a considerable body of evidence favours SCG compared to placebo and, far from being ineffective, the drug appears to be effective particularly in older children. This article replaces a previously published version. DOI: 10.1002/pst.258.

Influenza pandemic intervention planning using InfluSim: pharmaceutical and non- pharmaceutical interventions

Background

Influenza pandemic preparedness plans are currently developed and refined on national and international levels. Much attention has been given to the administration of antiviral drugs, but contact reduction can also be an effective part of mitigation strategies and has the advantage to be not limited per se. The effectiveness of these interventions depends on various factors which must be explored by sensitivity analyses, based on mathematical models.

Methods

We use the freely available planning tool InfluSim to investigate how pharmaceutical and non-pharmaceutical interventions can mitigate an influenza pandemic. In particular, we examine how intervention schedules, restricted stockpiles and contact reduction (social distancing measures and isolation of cases) determine the course of a pandemic wave and the success of interventions.

Results

A timely application of antiviral drugs combined with a quick implementation of contact reduction measures is required to substantially protract the peak of the epidemic and reduce its height. Delays in the initiation of antiviral treatment (e.g. because of parsimonious use of a limited stockpile) result in much more pessimistic outcomes and can even lead to the paradoxical effect that the stockpile is depleted earlier compared to early distribution of antiviral drugs.

Conclusion

Pharmaceutical and non-pharmaceutical measures should not be used exclusively. The protraction of the pandemic wave is essential to win time while waiting for vaccine development and production. However, it is the height of the peak of an epidemic which can easily overtax general practitioners, hospitals or even whole public health systems, causing bottlenecks in basic and emergency medical care.

Pandemic influenza planning for children and youth: who's looking out for our kids?

Recent worldwide attention on influenza pandemics has mainly focused on planning and preparation. Some published plans appear to have missed some unique considerations relevant to children and youth, leaving a serious and potentially devastating gap in our pandemic response. This paper highlights those unique considerations and encourages health administrators and policy-makers to rise to the challenge and demonstrate leadership by ensuring that all institutions consider children and youth in their pandemic planning.