Impact of influenza virus infection as a cause of pediatric hospitalization

The effect of influenza vaccine in reducing the severity of clinical outcomes in patients with COVID-19: a systematic review and meta-analysis

Recent evidence suggests that vaccination against influenza may reduce the clinical outcomes of COVID-19. This study looked at the link between influenza vaccination and the severity of COVID-19 infection. We searched five databases until August 2021. We included studies that reported the relationship between influenza vaccination and COVID-19 outcomes. We pooled the data as risk ratio (RR) or mean difference (MD), with 95% confidence intervals (CIs), the data pooled using fixed and random effects models according to the heterogeneity of results. Sixteen observational studies with 191,496 COVID-19 patients were included. In terms of mechanical ventilation, our analysis showed a significant favor for the influenza vaccinated group over the non-vaccinated group (RR = 0.72, 95% CI [0.54, 0.96], P = 0.03). However, the analysis indicated no statistically significant differences between vaccinated and non-vaccinated groups in the term of mortality rate (RR = 1.20, 95% CI [0.71, 2.04], P = 0.50), hospital admissions (RR = 1.04, 95% CI [0.84, 1.29], P = 0.75), intensive care admissions (RR = 0.84, 95% CI [0.44, 1.62], P = 0.60). There were no significant differences between those who had received the influenza vaccine and those who had not in COVID-19 clinical outcomes, except for mechanical ventilation which showed a significantly lower risk in the influenza vaccinated group compared to the non-vaccinated one. However, future research is encouraged as our data have limitations, and the influenza vaccine is regularly updated. Also, this does not exclude the importance of the influenza vaccine during the COVID-19 pandemic.

The Flu Vaccination May Have a Protective Effect on the Course of COVID-19 in the Pediatric Population: When Does Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Meet Influenza?

Background In the midst of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, a lot more chaos could be anticipated in the flu season due to the coexistence of SARS-CoV-2 and influenza with almost similar epidemiologic and clinical features. Could this become a "twindemic" or "syndemic" if there is any viral interference occurs? We investigated the effect of influenza and pneumococcal vaccines on the disease course of SARS-CoV-2 in the pediatric population and the possibility of viral interference. Material and methods After approval from Institutional Review Board, a retrospective electronic chart review on 20 years and younger SARS-CoV-2 polymerase chain reaction (PCR) positive patients who visited Arkansas Children's Hospital System between February 1 to August 30, 2020, was performed. The clinical data was collected along with influenza and pneumococcal vaccination status of these patients. Results The results showed that viral interference may have played a role in the current flu and coronavirus disease 2019 (COVID-19) twindemic. SARS-CoV-2 and influenza may have significantly affected each other's epidemiological features. Conclusion Understanding the relationship and co-existence of other viruses alongside SARS-CoV-2 and knowing the vaccination status of the host population may help in deploying the right strategies to get the best outcomes.

A review of the indirect protection of younger children and the elderly through a mass influenza vaccination program in Japan

In the past, Japan's strategy for controlling influenza was to vaccinate schoolchildren based on the theory that this could reduce influenza epidemics in the community, and a special program to vaccinate schoolchildren against influenza was begun in 1962. However, the program was discontinued in 1994 because of lack of evidence that it had limited the spread of influenza in the community. In 2001, it was reported that a clear decrease in excess mortality had coincided with the timing of the schoolchild vaccination program. This decrease could have potentially occurred because elderly people were protected by herd immunity generated by the program. Moreover, the program protected the younger siblings of schoolchildren against influenza-associated encephalopathy. Finally, the program was effective in reducing the number of class cancellations and absenteeism from school. During the period when the program was in effect, Japanese schoolchildren served as a barrier against influenza in the community.

Impact of the availability of an influenza virus rapid antigen test on diagnostic decision making in a pediatric emergency department

OBJECTIVES

Fever is one of the most commonly seen symptoms in the pediatric emergency department. The objective of this study was to observe how the rapid testing for influenza virus impacts on the management of children with fever.

METHODS

We performed a review of our pediatric emergency department records during the 2008/2009 annual influenza season. The BinaxNow Influenza A+B test was performed on patients with the following criteria: age 1.0 to 16.0 years, fever greater than 38.5 °C, fever of less than 96 hours' duration after the onset of clinical illness, clinical signs compatible with acute influenza, and nontoxic appearance. Additional laboratory tests were performed at the treating physician's discretion.

RESULTS

The influenza rapid antigen test was performed in 192 children. One hundred nine (57%) were influenza positive, with the largest fraction (101 patients) positive for influenza A. The age distribution did not differ between children with negative and positive test results (mean, 5.3 vs. 5.1 years, not statistically significant). A larger number of diagnostic tests were performed in the group of influenza-negative patients. Twice as many complete blood counts, C-reactive protein determinations, lumbar punctures, and urinalyses were ordered in the latter group.

CONCLUSIONS

Rapid diagnosis of influenza in the pediatric emergency department affects the management of febrile children as the confirmation of influenza virus infection decreases additional diagnostic tests ordered.

Postexposure prophylaxis for influenza in pediatric wards oseltamivir or zanamivir after rapid antigen detection

BACKGROUND

Postexposure prophylaxis (PEP) using neuraminidase inhibitors against exposure to influenza virus has been well studied in household settings but not in nosocomial settings in pediatric wards.

METHODS

We used oseltamivir or zanamivir as PEP in our pediatric wards. All influenza cases were diagnosed by the influenza rapid diagnostic test.

RESULTS

Between 2003 and 2011, there were 20 nosocomial introductions of influenza (10 were A, 9 were B and 1 was undetermined). The index cases consisted of 17 inpatients, 2 parents and 1 medical staff member. The 17 inpatients had been admitted to the hospital for reasons other than infectious disease and they developed influenza after hospitalization. Among the 81 contacts, 28 (35%) were exposed to influenza A, and 52 (64%) were exposed to influenza B. The rate of secondary infection among contacts not given PEP was 29% (5/17), and the rate among contacts given PEP was significantly lower, 3% (2/63; P = 0.004). The 2 infected contacts who had been given PEP were both influenza B cases, and both had received oseltamivir. The contacts who received PEP within 24 hours (59), for influenza A (23) and those who received zanamivir (15) did not develop influenza. No adverse events were reported.

CONCLUSIONS

PEP using oseltamivir or zanamivir for unexpected occurrences of nosocomial influenza in pediatric wards is safe and effective. The influenza rapid diagnostic test that we used was helpful for detecting nosocomial influenza in children.

Very low pandemic influenza A (H1N1) 2009 mortality associated with early neuraminidase inhibitor treatment in Japan: analysis of 1000 hospitalized children

OBJECTIVE

There were many cases of pandemic influenza A (H1N1) 2009 (H1N1/09) in Japan during the 2009-2010 epidemic. They accounted for 16% of the total population (20.7 million/128 million), and 59% of the patients were children 15 years of age and under (12.2 million/20.7million). However, there were only 38 paediatric deaths. We analyzed the clinical manifestations and treatment of children hospitalized because of H1N1/09 infection in order to clarify the association between treatment with neuraminidase inhibitors and the low mortality rate.

METHODS

A retrospective chart review was performed on a total of 1000 paediatric inpatients.

RESULTS

The causes of the hospitalizations were respiratory complications in 651 cases (65.1%), neurological complications in 255 cases (25.5%) and other complications in 94 cases. Neuraminidase inhibitors, primarily oseltamivir, had been used to treat 984 (98.4%) of the 1000 patients, and in 88.9% of the patients, treatment with neuraminidase inhibitors was initiated within 48 h after the onset of illness. Only 12 (1.2%) of the 1000 patients underwent mechanical ventilation, and one patient died of H1N1/09 infection.

CONCLUSIONS

Although a high proportion of the patients in this study had severe respiratory complications, the case fatality rate was only 0.1%. The low mortality rate of children due to the H1N1/09 epidemic in Japan was probably attributable to the universal implementation of early treatment with neuraminidase inhibitors.

Long-acting neuraminidase inhibitor laninamivir octanoate (CS-8958) versus oseltamivir as treatment for children with influenza virus infection

We conducted a double-blind, randomized controlled trial to compare a long-acting neuraminidase inhibitor, laninamivir octanoate, with oseltamivir. Eligible patients were children 9 years of age and under who had febrile influenza symptoms of no more than 36-h duration. Patients were randomized to 1 of 3 treatment groups: a group given 40 mg laninamivir (40-mg group), a group given 20 mg laninamivir (20-mg group), and an oseltamivir group. Laninamivir octanoate was administered as a single inhalation. Oseltamivir (2 mg/kg of body weight) was administered orally twice daily for 5 days. The primary end point was the time to alleviation of influenza illness. The primary analysis included 184 patients (61, 61, and 62 in the 40-mg group, 20-mg group, and oseltamivir group, respectively). Laninamivir octanoate markedly reduced the median time to illness alleviation in comparison with oseltamivir in patients infected with oseltamivir-resistant influenza A (H1N1) virus, and the reductions were 60.9 h for the 40-mg group and 66.2 h for the 20-mg group. On the other hand, there were no significant differences in the times to alleviation of illness between the laninamivir groups and oseltamivir group for patients with influenza A (H3N2) or B virus infection. Laninamivir octanoate was well tolerated. The most common adverse events were gastrointestinal events. Laninamivir octanoate was an effective and well-tolerated treatment for children with oseltamivir-resistant influenza A (H1N1) virus infection. Further study will be needed to confirm clinical efficacy against influenza A (H3N2) or B virus infection. Its ease of administration is noteworthy, because a single inhalation is required during the course of illness.

Influenza-related hospitalisations in children

AIM

To describe the disease burden, clinical pattern and outcome of influenza-related hospitalisations in children.

METHODS

This is a retrospective study carried out in a regional hospital in Hong Kong. Children hospitalised with established diagnosis of influenza infection from January to June of 2005 were studied. Length of hospitalisation, demographic characteristics, symptoms, clinical diagnosis and complications of influenza infection were analysed.

RESULTS

Influenza A infection accounted for 93.5% of these hospitalisations. Children less than 5 years of age comprised 70% of admission. Highest rate of admission occurred in May and April. One fourth of emergency admission during the study period and over 70% in the peak season was a result of influenza-related illness. Underlying medical disease was observed in 14.6% of children. Mean duration of hospitalisation was 3.0 days. Fever was the commonest presenting symptoms. Fever lasting for 7 days or more was observed in one-fifth of patients. Respiratory tract diseases (upper and lower) were the most frequent non-neurological diagnosis. Febrile convulsion was the complication observed in 27.6% of admission. One patient died as a result of acute necrotising encephalopathy.

CONCLUSION

Influenza contributed to heavy health-care burden. Mortality was rare but did occur. Hospitalisations occurred in both healthy children and those with underlying chronic illness. Young children played an important role in such hospitalisations. Means to prevent influenza-associated morbidity and mortality especially among young children are needed.

The burden of influenza in East and South-East Asia: a review of the English language literature

Abstract  While human infections with avian influenza A (H5NI) viruses in Asia have prompted concerns about an influenza pandemic, the burden of human influenza in East and Southeast Asia has received far less attention. We conducted a review of English language articles on influenza in 18 countries in East and Southeast Asia published from 1980 to 2006 that were indexed on PubMed. Articles that described human influenza‐associated illnesses among outpatients or hospitalized patients, influenza‐associated deaths, or influenza‐associated socioeconomic costs were reviewed. We found 35 articles from 9 countries that met criteria for inclusion in the review. The quality of articles varied substantially. Significant heterogeneity was noted in case definitions, sampling schemes and laboratory methods. Early studies relied on cell culture, had difficulties with specimen collection and handling, and reported a low burden of disease. The recent addition of PCR testing has greatly improved the proportion of respiratory illnesses diagnosed with influenza. These more recent studies reported that 11–26% of outpatient febrile illness and 6‐14% of hospitalized pneumonia cases had laboratory‐confirmed influenza infection. The influenza disease burden literature from East and Southeast Asia is limited but expanding. Recent studies using improved laboratory testing methods and indirect statistical approaches report a substantial burden of disease, similar to that of Europe and North America. Current increased international focus on influenza, coupled with unprecedented funding for surveillance and research, provide a unique opportunity to more comprehensively describe the burden of human influenza in the region.

Respiratory virus infections

The respiratory tract is a frequent site of infection with a wide range of viruses. Each family of viruses can cause differing clinical syndromes depending on the age of the patient and the immune response. As a corollary, different clinical syndromes can be caused by different families of viruses.

Rates of hospitalisation for influenza, respiratory syncytial virus and human metapneumovirus among infants and young children

To inform the development of a national influenza immunisation programme and the potential role of antiviral drugs in young children, we studied 613 children aged 71 months or younger who attended Leicester Childrens' Hospital during winter 2001-2002. During periods of respiratory syncytial virus (RSV), influenza, and human metapneumovirus activity, an estimated 12.2% (95% CI: 11.4-13.1), 7.1% (6.3-7.9), and 2.5% (2.1-2.9), respectively, of all medical cases assessed in the hospital were associated with these infections. The respective rates of hospital assessments for RSV, influenza, and human metapneumovirus (HMPV) were 1042 (95% CI: 967-1021), 394 (348-443), and 223 (189-262) per 100,000 children, and for admissions were 517 (465-574), 144 (117-175), and 126 (101-156) per 100,000. Few children with influenza had a prior risk factor. Children with influenza were admitted a median of 4 days after onset of illness and none was coded at discharge as influenza. We conclude that antivirals have little role in the hospital management of children with influenza. Our data provide health economists with information to evaluate the place of universal immunisation of young children against influenza. Hospitalisation rates decreased markedly with referral age, so vaccine would need to be given in early infancy for maximum benefit.

Mass Vaccination of Schoolchildren against Influenza and Its Impact on the Influenza-Associated Mortality Rate among Children in Japan

BACKGROUND

Influenza control based on mass vaccination of schoolchildren was implemented in Japan in the 1960s and was associated with a decrease in the overall mortality rate. The program was discontinued in 1994. The discontinuation was followed by a seasonal increase in the mortality rate. Lately, young children and elderly persons have been receiving influenza vaccines. The purpose of this study was to investigate changes in influenza-related mortality among young children before and after discontinuation of mass vaccination of schoolchildren.

METHODS

We calculated the monthly all-cause mortality rates during 1972-2003 and the pneumonia and influenza (P&I) mortality rates during 1972-1999 for young children (age, 1-4 years). We estimated the excess mortality rates attributable to influenza by computing the baseline annual mortality rate as a centered, 3-year moving average of the number of deaths reported during the 2 preceding and the following Decembers.

RESULTS

Prominent winter peaks in monthly all-cause mortality rates among young children occurred in the 1990s. They coincided with the winter peaks in monthly P&I mortality rates among young children and were very similar to the winter peaks observed among elderly persons. The number of excess deaths of young children was estimated to be 783 in the 11 winter seasons from 1990 to 2000, whereas no winter peaks in the number of deaths were seen after 2000.

CONCLUSIONS

It is likely that discontinuation of mass vaccination of schoolchildren was responsible for the increase in influenza-associated deaths among young children in the 1990s. The recent increase in influenza vaccinations among young children, together with the routine therapeutic use of neuraminidase inhibitors, has led to a decrease in the influenza-associated mortality rate.

Recurrence of febrile seizures in the respiratory season is associated with influenza A

OBJECTIVES

To investigate the association of viral infections and febrile seizures (FS).

STUDY DESIGN

From April 1998 to April 2002, a prospective, population-based study was carried out among general practitioners to assess the incidence of FS in their practices. Data thus obtained were compared with the incidence of common viral infections recorded in a national registry. Poisson regression analysis was performed to investigate whether the season or the type of infection was associated with the variation observed in FS incidence.

RESULTS

Throughout the 4-year period, 267 of 303 (88%) of general practitioners in the Dutch province of Friesland participated in the study. The estimated observation period was approximately 160,000 patient-years. We registered 654 cases of FS in 429 children. The estimated incidence of FS was 2.4 in 1000 patient-years. Poisson regression analysis revealed a positive correlation between recurrent FS and influenza A ( P = .01).

CONCLUSIONS

Our study suggests a relation between recurrent FS and influenza A. Influenza vaccination should be considered in all children with a history of FS.

The impact of influenza viruses on hospitalizations in infants younger than two years old during epidemics of respiratory syncytial virus infection

In order to evaluate the association of influenza viruses with hospitalizations for acute respiratory infection in infants younger than two years old during epidemics of respiratory syncytial virus infection, we studied 512 nasal washes from this population. The samples were obtained from 1997 to 2000. A total of 337 viruses were isolated: 264 respiratory syncytial viruses, 62 influenza viruses, eight parainfluenza viruses, two adenovirus and one rhinovirus. Hospitalizations for acute respiratory infection were owing to influenza and respiratory syncytial viruses in 18.3% vs. 78.3% of all cases, and 32.5% vs. 65.8%, respectively, in the group of infants between 6 months and 2 years old.

Influenza A and B virus infections in children

To obtain data on the clinical manifestations of infection, the age distribution, and the underlying conditions of children with influenza severe enough to lead to hospital referral, we performed a retrospective study of children treated at Turku University Hospital (Turku, Finland) in 1980-1999. Influenza A or B antigen was detected in the nasopharyngeal aspirates of 683 of the 15,420 children studied. The median age of children with influenza A was 2.0 years (n=544), and that of children with influenza B was 4.2 years (n=139) (P<.001). One-fourth of the children had an underlying medical condition. High fever, cough, and rhinorrhea were the most frequently recorded symptoms. Acute otitis media developed in 24% of the children, and pneumonia developed in 9% of the children. The study shows that the majority of patient hospitalizations for pediatric influenza involve previously healthy infants and young children. Laboratory confirmation of influenza is particularly important for children because the clinical presentation of the infection is less characteristic than that seen in adults.

Influenza-related hospitalizations among children in Hong Kong

BACKGROUND

It has been difficult to define the burden of influenza in children because of confounding by the cocirculation of respiratory syncytial virus (RSV). In Hong Kong, China, the influenza and RSV infection seasons sometimes do not overlap, thus providing an opportunity to estimate the rate of influenza-related hospitalization in a defined population, free from the effects of RSV.

METHODS

In a retrospective, population-based study, we estimated the influenza-associated excess rate of hospitalization among children 15 years old or younger in the Hong Kong Special Administrative Region from 1997 to 1999. Data from a single hospital with intensive use of virologic analyses for diagnosis were obtained to define and adjust for underestimation of the model.

RESULTS

Peaks of influenza and RSV infection activity were well separated in 1998 and 1999 but overlapped in 1997. The adjusted rates of excess hospitalization for acute respiratory disease that were attributable to influenza were 278.5 and 288.2 per 10,000 children less than 1 year of age in 1998 and 1999, respectively; 218.4 and 209.3 per 10,000 children 1 to less than 2 years of age; 125.6 and 77.3 per 10,000 children 2 to less than 5 years of age; 57.3 and 20.9 per 10,000 children 5 to less than 10 years of age; and 16.4 and 8.1 per 10,000 children 10 to 15 years of age.

CONCLUSIONS

In the subtropics, influenza is an important cause of hospitalization among children, with rates exceeding those reported for temperate regions.

Viral etiology of acute respiratory infections among children in Porto Alegre, RS, Brazil

Although acute respiratory infections (ARIs) are a major cause of child morbidity and mortality in Southern Brazil, little information is available on their seasonality and viral etiology. This study was conducted on children under 5 years of age with ARI to assess viral etiology in the State of Rio Grande do Sul, from 1990 to 1992. A total of 862 nasopharyngeal secretion (NPS) samples were tested using indirect immunofluorescence. The results showed that 316 (36.6%) NPS samples were positive: 26.2% for RSV, 6% for adenovirus, 1.7% for influenza viruses, 1.5% for parainfluenza viruses, and 1.2% for mixed infection. The mean viral prevalence rates in out-patient services, emergency wards, and in-patient hospital wards were 26.7%, 53% and 42.3%, respectively. Respiratory syncytial virus (RSV) and adenovirus accounted for 91.4 % of the viral diagnoses. RSV was more frequent in children under one year of age at the three levels of health care and was prevalent in infants under six months. Adenovirus was the most prevalent pathogen in hospitalized children, in 1992. Influenza A virus showed an increased prevalence with age among out-patient children. This study shows the annual occurrence of viral respiratory infections in the coldest months, with a significant annual variation in the frequency of RSV infection.

Bedside diagnosis of influenzavirus infections in hospitalized children

OBJECTIVE

For preventing nosocomial influenza infections and to facilitate prompt antiviral therapy, an accessible, rapid diagnostic method for influenzavirus is needed. We evaluated the performance of a lateral-flow immunoassay (QuickVue Influenza Test) completed at the bedside of hospitalized children during the influenza season.

METHODS

All children who were evaluated at a large teaching hospital during the 1999 to 2000 influenza season were eligible if they were 1) younger than 19 years and hospitalized with respiratory symptoms or 2) younger than 3 years and hospitalized with fever. Each study child had 2 nasal swabs obtained--1 for influenzavirus culture and polymerase chain reaction (PCR) and the other for the QuickVue Influenza Test. The performance of the rapid diagnostic test was compared with the results of culture or PCR for influenza A or B.

RESULTS

Of 303 eligible children, 233 (77%) were enrolled. In this population, 19 children had culture- and/or PCR-confirmed influenza A infection, prevalence of 8%. The QuickVue Influenza Test had a sensitivity of 74%, specificity of 98%, positive predictive value of 74%, and negative predictive value of 98%.

CONCLUSIONS

Among children hospitalized with fever/respiratory symptoms during the influenza season, negative bedside QuickVue Influenza Tests indicated very low likelihood of influenza infection, whereas positive tests greatly increased the probability of influenza-associated illness.

Clinical courses of croup caused by influenza and parainfluenza viruses

Influenza viruses have occasionally been associated with severe manifestations of croup, but no comparative studies of different viral etiologies are available. In a retrospective study we compared the clinical courses of croup caused by influenza and parainfluenza viruses in hospitalized children. By several indicators the clinical picture of croup caused by influenza viruses was significantly more severe than that caused by parainfluenza viruses.

Influenza A infection is an important cause of febrile seizures

OBJECTIVES

To compare the incidence of febrile seizures in children hospitalized for influenza A infection with parainfluenza and adenovirus infection and to examine the hypothesis that children hospitalized for influenza A (variant Sydney/H3N2) during the 1998 season in Hong Kong had more frequent and refractory seizures when compared with other respiratory viruses, including the A/Wuhan H3N2 variant that was present in the previous year.

METHODS

Medical records of children between 6 months and 5 years of age admitted for influenza A infection in 1998 were reviewed. For comparison, records of children of the same age group with influenza A infection in 1997, and with parainfluenza and adenovirus infections between 1996 and 1998 were reviewed. Children who were afebrile or who had an underlying neurologic disorder were excluded.

RESULTS

Of children hospitalized for influenza A in 1998 and 1997, 54/272 (19.9%) and 27/144 (18.8%) had febrile seizures, respectively. The overall incidence of febrile seizures associated with influenza A (19.5%) was higher than that in children hospitalized for parainfluenza (18/148; 12.2%) and adenovirus (18/199; 9%) infection, respectively. In children who had febrile seizures, repeated seizures were more commonly associated with influenza A infection than with parainfluenza or adenovirus infection (23/81 [28%] vs 3/36 [8.3%], odds ratio [OR] 4.3, 95% confidence interval: 1.2 to 15.4). Alternatively, children with influenza A infection had a higher incidence (23/416, 5.5%) of multiple seizures during the same illness than those with adenovirus or parainfluenza infection (3/347, 0.86%; OR 6.7, 95% confidence interval: 2.0-22.5.) The increased incidence of febrile seizures associated with influenza A was not attributable to differences in age, gender, or family history of febrile seizure. Multivariate analysis, adjusted for peak temperature and duration of fever, showed that hospitalized children infected with infection A had a higher risk of febrile seizures than those who were infected with parainfluenza or adenovirus (OR 1.97). Influenza A infection was a significant cause of febrile seizure admissions. Of 250 and 249 children admitted to Queen Mary Hospital for febrile seizures in 1997 and 1998, respectively, influenza A infection accounted for 27 (10.8%) admissions in 1997 and 54 (21.7%) in 1998. During months of peak influenza activity, it accounted for up to 35% to 44% of febrile seizure admissions. In contrast, parainfluenza, adenovirus, respiratory syncytial virus, and influenza B had a smaller contribution to hospitalizations for febrile seizures, together accounting for only 25/250 (10%) admissions in 1997 and 16/249 (6.4%) in 1998.

CONCLUSION

The influenza A Sydney variant (H3N2) was not associated with an increased risk of febrile seizures when compared with the previous influenza A Wuhan variant (H3N2) or H1N1 viruses. However, in hospitalized children, influenza A is associated with a higher incidence of febrile seizures and of repeated seizures in the same febrile episode than are adenovirus or parainfluenza infections. The pathogenesis of these observations warrants additional studies. Complex febrile seizures, particularly multiple febrile seizures at the time of presentation, have been thought to carry an adverse long-term prognosis because of its association with a higher incidence of epilepsy. Repeated febrile seizures alone, particularly if associated with influenza A infection, may not be as worrisome as children with complex febrile seizures because of other causes, which requires additional investigation. This may subsequently have an impact on reducing the burden of evaluation in a subset of children with complex febrile seizures.

Cost-effectiveness of influenza vaccination in high-risk children in Argentina

OBJECTIVES

our study aimed to evaluate the cost-effectiveness of influenza vaccination in high-risk children in Argentina.

METHODS

a decision analysis model was performed, using data from published and unpublished sources, to compare two strategies--to vaccinate or not to vaccinate. We simulated the expected consequences of vaccination on direct medical costs, related to disease management and indirect costs, related to lost parental working days (absenteeism).

RESULTS

Using base-case assumptions vaccination of high-risk children aged 6 months to 15 years old, in Argentina (estimated cohort of 1184748) would prevent 207331 cases of influenza, resulting in a reduction of 58052 days of hospitalization and 207331 outpatient visits. Vaccination would lead to net savings of US$ 11894870 per vaccinated cohort (US$ 10.04 per vaccinated child).

CONCLUSION

our economic analysis shows that in Argentina, routine vaccination of high-risk children against influenza would be cost saving for society.

Critical influenza virus infection

OBJECTIVE

To determine the risk of death from influenza infection in children with chronic underlying disease.

METHODOLOGY

An 18-year retrospective study of children with 'critical' influenza A or B virus infection, defined as requiring admission to intensive care or resulting in death, but excluding laryngotracheobronchitis (LTB). Influenza infection was diagnosed by viral culture and/or immunofluorescence of respiratory secretions. Patients with LTB were analysed separately.

RESULTS

There were 27 cases of critical influenza virus infection over the study period, comprising 26 admissions to the intensive care unit (excluding LTB) and one death on the general wards. Thirteen (48%) of the 27 children had chronic underlying disease. In addition, 12 children with LTB were admitted to the intensive care unit. The LTB children were older and less likely to have chronic underlying disease. Nosocomial infection caused seven (26%) of the 27 critical infections. Nine (33%) of the 27 children with critical influenza died. Six (46%) of 13 children with chronic underlying disease and influenza admitted to intensive care died, compared with three of 14 (21%) without any underlying disease (odds ratio = 3.1, 95% confidence interval 0.6-14.0).

CONCLUSIONS

Critical life-threatening influenza virus infection was uncommon, but the mortality was high (33%), particularly in children with chronic underlying disease. Nosocomial infection with influenza was an important cause of admission to intensive care.

Effect of rapid diagnosis on management of influenza A infections

BACKGROUND

Few studies have examined the impact of rapid viral diagnostic tests on patient management.

OBJECTIVE

To assess the effect of rapid diagnosis of influenza A infections on patient management.

METHODS

The medical records of children with respiratory infections who were evaluated at a children's hospital between July 1, 1995, and June 30, 1997, were reviewed. Children (n = 56) evaluated in the Emergency Department (ED) who had a positive influenza A enzyme immunoassay (EIA) were compared with two control groups for the likelihood of admission, antibiotic use and duration of hospitalization and antibiotic administration.

RESULTS

Patients discharged from the ED with a positive EIA test were less likely to receive antibiotics than those with a negative EIA test (20% vs. 53%; P = 0.04). Patients admitted to the hospital with a positive EIA test were as likely to receive antibiotics as those without a rapid diagnosis, but the duration of antibiotic administration was significantly shorter in the group with a positive EIA test (3.5 vs. 5.4 days; P = 0.03). Patients with a positive EIA test also were more likely to receive antiviral therapy than either control group (25% vs. 0 and 1.8%; P < 0.001).

CONCLUSIONS

The detection of influenza A by EIA has a positive impact on medical management by decreasing antibiotic use in pediatric patients evaluated in an ED, by decreasing the duration of antibiotic use in hospitalized patients and by encouraging antiviral therapy.

Comparison of a new neuraminidase detection assay with an enzyme immunoassay, immunofluorescence, and culture for rapid detection of influenza A and B viruses in nasal wash specimens

The performance of a new, rapid, easy-to-perform assay based on neuraminidase enzyme activity for detection of influenza virus types A and B was compared to detection by culture, indirect immunofluorescence, and enzyme immunoassay in 479 nasal wash specimens from children with respiratory infections. Compared to isolation of influenza virus by culture, the neuraminidase assay had a sensitivity of 70.1%, specificity of 92.4%, positive predictive value of 76.3%, and negative predictive value of 89.9%. There was a higher sensitivity for the detection of influenza A virus (76.4%) than for influenza B virus (40.9%). Indirect immunofluorescence showed a sensitivity of 59.8% and specificity of 97% compared to culture isolation for detection of influenza A and B viruses. Enzyme immunoassay showed a sensitivity of 89.7% and specificity of 98.1% for the detection of influenza A alone. The quality of the nasal wash specimen had a significant effect on the detection of influenza virus by all of the assays. A strong response of the neuraminidase assay was more likely to represent a culture-confirmed influenza infection. This new rapid neuraminidase assay was useful for the detection of influenza A and B viruses in nasal wash specimens.

Influenza

Influenza is an acute respiratory illness of global importance that causes considerable morbidity and mortality every year. At the beginning of the millennium, influenza will still be an emergent or re-emergent infection because of the viral ability to mutate. Global influenza surveillance indicates that influenza viruses may vary within a country and between countries and continents during an influenza season. Virologic surveillance is of critical importance in monitoring antigenic shift and drift. Disease surveillance is important in assessing the impact of the epidemics. Both types of information provide the basis of vaccine composition and the correct use of antivirals. Laboratory diagnosis is of critical importance for the global surveillance of influenza and may allow the timely use of antiviral drugs. Viral isolation remains the gold standard for laboratory diagnosis; however, several new rapid diagnostic tests are available or in development. The clinical spectrum of the disease varies from asymptomatic infection to the classic flu syndrome, and respiratory and nonrespiratory complications are observed particularly in high-risk groups. Current inactivated influenza vaccines have shown efficacy and effectiveness in preventing influenzalike illness, hospitalization for pneumonia, and death and in reducing health care costs. Because of the annual administration of the vaccine and the short period of time where it can be administered, strategies directed at improving vaccine coverage are of critical importance. In this sense, experiences obtained in different countries, such as with the National Immunization Campaigns developed in Argentina, provide one model of massive vaccine administration. In addition to current vaccines, new live attenuated vaccines will permit a most effective prevention of influenza in the community in the near future. A new type of antiviral, neuraminidase inhibitors, offers valuable benefits in the prevention and treatment of influenza A and B. A future pandemic of influenza seems inevitable. There is wide recognition that preparation for the next pandemic requires that infrastructure be in place during interpandemic periods for implementing preventive and therapeutic measures. The WHO has established a pandemic influenza task force, and a number of countries in Latin America have developed formal pandemic plans. These national and international efforts are essential to reduce the mortality and morbidity in the next influenza pandemic.

[Seroepidemiological survey for influenza virus in Belém, Pará, Brazil, 1992-1993]

A seroepidemiological study was carried out from 1992 to 1993 to estimate the prevalence of antibody to prevailing influenza virus strains circulating among patients attending the IEC Virology Laboratory in Belem, Northern Brazil. A total of 179 (11%) of serum samples were obtained during the post-epidemic period and processed by the hemagglutination inhibition test against the A/Taiwan/1/86 (H1N1), A/Beijing/353/89 (H3N2), and B/Yamagata/16/88 types of influenza virus. The serological results indicate circulation of viruses antigenically related to all three strains during the two-year study period. In 1992, the overall prevalence rates of HI antibodies to H1N1 and H3N2 were 84% and 56%, respectively. Presence of antibodies to both strains was detected in all age groups, suggesting intense viral activity that year. Antibodies to influenza B were detected at lower levels in all patients during this period. Similar prevalence to the H1N1 virus was noted in 1993, indicating that this strain occurred in both years. However, an increase in prevalence rates for the H3N2 virus was seen in 1993, suggesting that this strain (or a related virus) circulated intensively during this year. Influenza B activity also increased in 1993, causing infection mainly among young adults.

Large sequential outbreaks caused by influenza A (H3N2) and B viruses in an institution for the mentally handicapped

During the mixed epidemic caused by influenza A (H3N2) and B in the 1992-1993 season in Japan, large sequential outbreaks occurred in an institution for mentally handicapped people where none of the residents or staff members had been immunized. During the influenza A outbreak (A/ Beijing/32/92-like strain) in January, 37.0% of the residents (85/230) and 31.4% of the staff (75/239) had an influenza-like illness. During the influenza B outbreak (B/Panama/45/90- and B/Beijing/184/ 93-like strain) in late February, 59.0% of the residents and 24.3% of the staff had an influenza-like illness. As many as 25.2% of the residents had two episodes of influenza-like illness during the season, as opposed to only 5.4% of the staff members. Mixed epidemics probably have a severe impact on institutionalized high-risk people, adversely affecting them almost twice as much as influenza epidemics caused by a single virus.

Prevalence of Chlamydia pneumoniae in acute lower respiratory infection in the pediatric population in Japan

Chlamydia pneumoniae has been established as an important etiologic agent of acute respiratory tract infection in humans, especially in adults. However, there is little information available on C. pneumoniae infection in the pediatric age group. The microimmunofluorescence test and Chlamydia pneumoniae-specific polymerase chain reaction (PCR) method were applied to reveal the role of C. pneumoniae as an etiologic agent of acute lower respiratory tract infection in children in Japan. Among 136 patients aged between 2 months and 15 years with acute lower respiratory tract infection, five patients with pneumonia were found to have recent C. pneumoniae infection by the microimmunofluorescence test. C. pneumoniae-specific PCR products were detected from specimens of four patients among these five. Neither C. trachomatis nor C. psittaci infection was found in this population. These results suggest that C. pneumoniae is an important causative agent of acute childhood pneumonia and may be the most prevalent pathogen among the genus Chlamydia that causes acute lower respiratory disease in this age group in Japan.