Influenza virus shedding—Excretion patterns and effects of antiviral treatment

Risk period for transmission of SARS-CoV-2 and seasonal influenza: a rapid review

BACKGROUND

Restricting infectious healthcare workers (HCWs) from the workplace is an important infection prevention strategy. The duration of viral shedding or symptoms are often used as proxies for the infectious period in adults but may not accurately estimate it.

OBJECTIVE

To determine the risk period for transmission among previously healthy adults infected with SARS-CoV-2 omicron variant (omicron) or influenza A (influenza) by examining the duration of shedding and symptoms, and day of symptom onset in secondary cases of transmission pairs.

DESIGN

Rapid review.

METHODS

This rapid review adhered to PRISMA-ScR; five databases were searched. The cumulative daily proportion of participants with an outcome of interest was calculated for each study and summarized.

RESULTS

Forty-three studies were included. Shedding resolved among ≥ 70% of participants by the end of day nine post symptom onset for omicron, and day seven for influenza; and for ≥ 90% of participants, by the end of day 10 for omicron and day nine for influenza. Two studies suggested shedding continues > 24 hours post-fever resolution for both viruses. Symptom onset occurred in ≥ 80% of secondary cases by the end of day seven post-primary case symptom onset for omicron and day six for influenza.

CONCLUSIONS

Omicron shedding is consistent with previous recommendations to exclude infected HCWs from work for 10 days; and influenza follows a similar trend. Earlier symptom onset in most secondary cases for both pathogens indicates that, despite persistent viral shedding, most transmission occurs earlier; and the cumulative serial interval might better approximate the duration of infectiousness.

The 1978 English boarding school influenza outbreak: where the classic SEIR model fails

Previous work has failed to fit classic SEIR epidemic models satisfactorily to the prevalence data of the famous English boarding school 1978 influenza A/H1N1 outbreak during the children's pandemic. It is still an open question whether a biologically plausible model can fit the prevalence time series and the attack rate correctly. To construct the final model, we first used an intentionally very flexible and overfitted discrete-time epidemiologic model to learn the epidemiological features from the data. The final model was a susceptible (S) - exposed (E) - infectious (I) - confined-to-bed (B) - convalescent (C) - recovered (R) model with time delay (constant residence time) in E and I compartments and multi-stage (Erlang-distributed residence time) in B and C compartments. We simultaneously fitted the reported B and C prevalence curves as well as the attack rate (proportion of children infected during the outbreak). The non-exponential residence times were crucial for good fits. The estimates of the generation time and the basic reproductive number ([Formula: see text]) were biologically reasonable. A simplified discrete-time model was built and fitted using the Bayesian procedure. Our work not only provided an answer to the open question, but also demonstrated an approach to constructive model generation.

Prolonged SARS-CoV-2 Viral Shedding in Patients with COVID-19 was Associated with Delayed Initiation of Arbidol Treatment and Consulting Doctor Later: A Retrospective Cohort Study

Objective

To study data about SARS-CoV-2 virus shedding and clarify the risk factors for prolonged virus shedding.

Methods

Data were retrospectively collected from adults hospitalized with laboratory-confirmed coronavirus disease-19 (COVID-19) in Wuhan Union Hospital. We compared clinical features among patients with prolonged (a positive SARS-CoV-2 RNA on day 23 after illness onset) and short virus shedding and evaluated risk factors associated with prolonged virus shedding by multivariate regression analysis.

Results

Among 238 patients, the median age was 55.5 years, 57.1% were female, 92.9% (221/238) were administered with arbidol, 58.4% (139/238) were given arbidol in combination with interferon. The median duration of SARS-CoV-2 virus shedding was 23 days (IQR, 17.8–30 days) with a longest one of 51 days. The patients with prolonged virus shedding had higher value of D-dimer (P=0.002), IL-6 (P<0.001), CRP (P=0.005) and more lobes lung lesion (P=0.014) on admission, as well as older age (P=0.017) and more patients with hypertension (P=0.044) than in those the virus shedding less than 23 days. Multivariate regression analysis revealed that prolonged viral shedding was significantly associated with initiation arbidol >8 days after symptom onset [OR: 2.447, 95% CI (1.351–4.431)], ≥3 days from onset of symptoms to first medical visitation [OR: 1.880, 95% CI (1.035–3.416)], illness onset before Jan. 31, 2020 [OR: 3.289, 95% CI (1.474–7.337)]. Arbidol in combination with interferon was also significantly associated with shorter virus shedding [OR: 0.363, 95% CI (0.191–0.690)].

Conclusion

Duration of SARS-CoV-2 virus shedding was long. Early initiation of arbidol and arbidol in combination with interferon as well as consulting doctor timely after illness onset were helpful for SARS-CoV-2 clearance.

Electronic Supplementary Material

Supplementary material is available for this article at 10.1007/s11596-021-2434-y and is accessible for authorized users.

Current and Novel Approaches in Influenza Management

Influenza is a disease that poses a significant health burden worldwide. Vaccination is the best way to prevent influenza virus infections. However, conventional vaccines are only effective for a short period of time due to the propensity of influenza viruses to undergo antigenic drift and antigenic shift. The efficacy of these vaccines is uncertain from year-to-year due to potential mismatch between the circulating viruses and vaccine strains, and mutations arising due to egg adaptation. Subsequently, the inability to store these vaccines long-term and vaccine shortages are challenges that need to be overcome. Conventional vaccines also have variable efficacies for certain populations, including the young, old, and immunocompromised. This warrants for diverse efficacious vaccine developmental approaches, involving both active and passive immunization. As opposed to active immunization platforms (requiring the use of whole or portions of pathogens as vaccines), the rapidly developing passive immunization involves administration of either pathogen-specific or broadly acting antibodies against a kind or class of pathogens as a treatment to corresponding acute infection. Several antibodies with broadly acting capacities have been discovered that may serve as means to suppress influenza viral infection and allow the process of natural immunity to engage opsonized pathogens whilst boosting immune system by antibody-dependent mechanisms that bridge the innate and adaptive arms. By that; passive immunotherapeutics approach assumes a robust tool that could aid control of influenza viruses. In this review, we comment on some improvements in influenza management and promising vaccine development platforms with an emphasis on the protective capacity of passive immunotherapeutics especially when coupled with the use of antivirals in the management of influenza infection.

Prospective evaluation of diagnostic tools for respiratory viruses in children and adults

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Molecular techniques have considerably improved sensitivity of viral diagnosis.

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Interpretation of results can be delicate as DNA or RNA traces can be detected.

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Their use is hindered by their cost and the difficulty to absorb high workloads.

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Their impact in management of patients still has to be demonstrated.

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Tertiary care hospitals should provide a testing algorithm to suit each case.

Aim

To compare the performances of molecular and non-molecular tests to diagnose respiratory viral infections and to evaluate the pros and contras of each technique.

Methods

Two hundred ninety-nine respiratory samples were prospectively explored using multiplex molecular techniques (FilmArray Respiratory Panel, Clart Pneumovir), immunological techniques (direct fluorescent assay, lateral flow chromatography) and cell cultures.

Findings

Molecular techniques permitted the recovery of up to 50% more respiratory pathogens in comparison to non-molecular methods. FilmArray detected at least 30% more pathogens than Clart Pneumovir which could be explained by the differences in their technical designs. The turnaround time under 2 hours for the FilmArray permitted delivery of results when patients were still in the emergency room.

Incidence of antiviral drug resistance markers among human influenza A viruses in the Eastern Mediterranean Region, 2005-2016

BACKGROUND

Two classes of antiviral drugs are available for influenza antiviral therapy: the adamantanes and the neuraminidase inhibitors (NAIs). Due to the emergence of adamantane-resistant variants, the use of these drugs has been largely limited in the world. The NAIs became the drugs of choice for treatment of influenza A infections. However, amino acid substitutions in the NA protein might lead to reduced sensitivity to NAIs.

METHODS

The frequency and distribution of matrix protein 2 (M2) and neuraminidase (NA) variants which confer resistance to antiviral drugs was investigated in the Eastern Mediterranean Region (EMR) between 2005 and 2016. A total of 314 M2 and 1209 NA protein sequences from influenza A/H1N1, A/H1N1pdm09, A/H3N2, and A/H5N1 available in the public database were analyzed.

RESULTS

Eighty-six percent of the influenza A viruses detected in the EMR were resistant to adamantanes, among which, H3 strains exhibited the highest (95.32%) level of adamantane resistance. Approximately 98.51% (265/269) of influenza A/H1N1 and H3N2 resistant viruses had the S31N substitution in their M2 sequences. The V27A mutation was the only resistance marker found in A/H5N1 viruses and was detected at a frequency of 7.40% among the investigated viruses. Other resistant mutations L26F, A30T, G34E, and L38F were not detected in any of the variants. We found that 2.81% (n = 34) of the detected NA sequences from influenza A viruses possessed at least one NAI-resistant mutation and the vast majority of resistant viruses 79.41% (27/34) bear the H274Y mutation. The frequency of NAI-resistant viruses was 3.29% (24/729) for the H1N1pdm09, 10.64% (5/47) for the seasonal H1N1, and 4.06% (5/123) for H5N1 viruses. None of the H3N2 viruses analyzed during the study period were resistant to NAIs.

CONCLUSION

Our study reveals the emergence and spread of antiviral drug resistant influenza A viruses in the EMR and emphasizes the importance of continuous surveillance to maintain the effective use of the current antivirals.

Community pharmacy rapid influenza A and B screening: A novel approach to expedite patient access to care and improve clinical outcomes

OBJECTIVE

To investigate the impact and feasibility of community pharmacist-directed influenza screening and to evaluate the proportion of influenza-positive cases that resulted in the initiation of antiviral therapy by pharmacists.

METHODS

Patients aged 5 and older with symptoms suggestive of influenza were recruited at 2 Shoppers Drug Mart locations in Toronto, Ontario, from December 12, 2014, to February 4, 2015. Nasal swabs were collected by pharmacists and screened using the BD Veritor system for Rapid Detection of Flu A+B. Positive tests for influenza were reported to patients' physicians and recommendations for antiviral therapy were made when indicated. Supportive care recommendations and telephone follow-up within 48 hours of assessment were provided to all patients.

RESULTS

A total of 59 patients participated in the influenza screening program. Sixty-one percent of patients were at high risk for influenza-related complications, while 15% had more than one risk factor. Thirty-four percent of patients screened positive for influenza, of which 100% were influenza A. Of the patients who screened positive, a prescription for oseltamivir was obtained in 40% of cases. The majority of prescriptions were provided directly to the pharmacy (63%), while the balance was provided after the patients underwent medical examination at the request of their physicians (37%). The pharmacy team offered supportive care to all patients for symptom management. Over-the-counter pharmacotherapy was provided to 85% of patients.

CONCLUSION

These results highlight the readiness of community pharmacists to participate in the management of patients with influenza and their ability to implement screening into pharmacy workflow. Community pharmacy-based influenza screening may facilitate prompt access to pharmacologic treatment for patients with influenza, as well as decrease burden on the health care system by redirecting influenza-negative patients from physicians' offices and hospitals. Timely physician communication remains a barrier to access to treatment, suggesting a potential key role for advanced pharmacist prescribing. Can Pharm J (Ott) 2016;149:83-89.

Factors associated with real-time RT-PCR cycle threshold values among medically attended influenza episodes

We evaluated the cycle threshold (CT) values of 1,160 influenza A positive and 806 influenza B positive specimens from two seasons of the US Flu VE Network to identify factors associated with CT values. Low CT values (high genomic load) were associated with shorter intervals between illness onset and specimen collection, young age (ages 3-8 years old), and self-rated illness severity for both influenza A and B. Low CT values were also associated with reported fever/feverishness and age ≥65 years for influenza A.

Prompt Oseltamivir Therapy Reduces Medical Care and Mortality for Patients With Influenza Infection: An Asian Population Cohort Study

There are limited population-based studies on the progress of oseltamivir therapy for influenza infection.Using insurance claims data of 2005, 2009, and 2010, the authors established an "in-time" cohort and a "lag-time" cohort representing influenza patients taking the medicine within and not within 1 week to examine the treatment progress. Incident outpatient visit, emergency care and hospitalization, and fatality were compared between the 2 cohorts in the first week and the second week of follow-up periods, after the oseltamivir therapy.A total of 112,492 subjects diagnosed with influenza on oseltamivir therapy in 2005, 2009, and 2010 were identified. The multivariate logistic regression analysis showed that the in-time treatment was superior to the lag-time treatment with less repeat outpatient visits, hospitalizations, and fatality. The overall corresponding in-time treatment to lag-time treatment odds ratios (OR) were 0.50, 0.54, and 0.71 (all P value < 0.05), respectively. The in-time to lag-time ORs of all events were 0.50 in 2009 and 0.54 in 2010.Our study demonstrates that the in-time oseltamivir therapy leads to significantly better treatment outcomes. Oseltamivir should be administered as early as the onset of influenza symptoms appears.

Evaluation of 3 rapid influenza diagnostic tests during the 2012-2013 epidemic: influences of subtype and viral load

This article evaluates the performance of 3 rapid influenza diagnostic tests (RIDTs), in correlation with the influenza subtypes and the viral load. A total of 236 samples were prospectively analyzed with BinaxNOW Influenza A/B, Directigen EZ Flu A and B, and bioNexia Influenza A+B. The results were compared to cell cultures and real-time polymerase chain reaction. Positive samples were further subtyped. Thirty-seven samples were positive for influenza A, and 57, for influenza B. For A(H1N1), the sensitivities were 71.42% for BinaxNOW, 78.57% for Directigen, and 67.85% for bioNexia. Eight samples were positive for A(H3N2), and only the bioNexia test had 1 false-negative result. Lowest sensitivities were observed for influenza B/Yamagata, (56.86% for BinaxNOW and Directigen and 39.21% for bioNexia). The 3 evaluated RIDTs were more efficient at detecting influenza A(H3N2) than for A(H1N1) and B/Yamagata. Highest viral loads in the samples were associated with better rate of detection.

Consistency of influenza A virus detection test results across respiratory specimen collection methods using real-time reverse transcription-PCR

In our prospective cohort study, we compared the performance of nasopharyngeal, oropharyngeal, and nasal swabs for the detection of influenza virus using real-time reverse transcription-PCR assay. Joint consideration of results from oropharyngeal and nasal swabs was as effective as consideration of results from nasopharyngeal swabs alone, as measured by sensitivity and noninferiority analysis.

Factors promoting the prolonged shedding of the pandemic (H1N1) 2009 influenza virus in patients treated with oseltamivir for 5 days

Background

The duration of viral shedding is an important determinant of infectivity and transmissibility and provides vital information for effective infection prevention and control. However, few studies have evaluated viral shedding in patients admitted to hospital with 2009 H1N1 influenza and treated with oseltamivir.

Objective

To determine the incidence of prolonged 2009 H1N1 influenza viral shedding in patients treated for 5 days with oseltamivir and to identify factors that promote prolonged viral shedding.

Methods

This was a prospective, observational cohort study of 173 patients infected with 2009 H1N1 influenza (confirmed by RT‐PCR) who were admitted to isolation rooms in the emergency department of our hospital between August 25, 2009 and December 31, 2009. All of the patients were treated according to institutional protocols and received routine follow‐up RT‐PCR testing after 5 days of oseltamivir therapy. Prolonged viral shedding was defined as a positive follow‐up RT‐PCR result.

Result

Of the 173 patients in our cohort, 88 (50·8%) showed persistent viral shedding after oseltamivir treatment. Viral shedding was significantly prolonged if antiviral therapy was started ≥2 days after symptom onset (OR 2·74, 95% CI 1·29–5·82), if there were major comorbidities (OR 3·07, 95% CI 1·29–7·32), and/or if respiratory symptoms were still present on the day 5 of antiviral treatment (OR 4·13, 95% CI 2·10–8·11).

Conclusions

The presence of major comorbidities, a delay in initiating antiviral treatment, and continuing respiratory symptoms after 5 days of antiviral treatment are associated with prolonged shedding of the 2009 H1N1 influenza virus.

Effectiveness of patient-collected swabs for influenza testing

OBJECTIVE

To compare the effectiveness of self-collected and health care worker (HCW)-collected nasal swabs for detection of influenza viruses and determine the patients' preference for type of collection.

PATIENTS AND METHODS

We enrolled adult patients presenting with influenzalike illness to the Emergency Department at Mayo Clinic, Rochester, Minnesota, from January 28, 2011, through April 30, 2011. Patients self-collected a midturbinate nasal flocked swab from their right nostril following written instructions. A second swab was then collected by an HCW from the left nostril. Swabs were tested for influenza A and B viruses by real-time reverse transcription-polymerase chain reaction, and percent concordance between collection methods was determined.

RESULTS

Of the 72 paired specimens analyzed, 25 were positive for influenza A or B RNA by at least one of the collection methods (34.7% positivity rate). When the 14 patients who had prior health care training were excluded, the qualitative agreement between collection methods was 94.8% (55 of 58). Two of the 58 specimens (3.4%) from patients without health care training were positive only by HCW collection, and 1 of 58 (1.7%) was positive only by patient self-collection. A total of 53.4% of patients (31 of 58) preferred the self-collection method over the HCW collection, and 25.9% (15 of 58) had no preference.

CONCLUSION

Self-collected midturbinate nasal swabs provide a reliable alternative to HCW collection for influenza A and B virus real-time reverse transcription-polymerase chain reaction.

Low attack rate of novel influenza A (H1N1) virus infection among healthcare workers: a prospective study in a setting with an elaborated containment plan

PURPOSE

This study aimed to determine incidence rates of novel influenza A (H1N1) infection among healthcare personnel with different exposure risks during the 2009 H1N1 pandemic.

METHODS

From August 2009 until April 2010, 66 healthcare workers from a 410 bed teaching hospital in Amsterdam were monitored. The following three different exposure groups were created: a high- (n = 26), intermediate- (n = 20), and low-risk group (n = 20). Throat swabs were collected each week and analyzed by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) in order to detect the H1N1 virus. Blood was drawn at study enrollment and once monthly thereafter, and serum specimens were tested with an H1N1-specific hemagglutination-inhibition serologic assay. Influenza-like signs and symptoms were assessed weekly.

RESULTS

One of 26 high-risk group participants proved H1N1 positive once by RT-PCR. This corresponds to an incidence rate in the high-risk group of 5.7/1,000 person weeks (95% CI 0-17/1,000). None of the intermediate- and low-risk group participants proved H1N1 positive by RT-PCR. Significant antibody titer rises in convalescent sera were demonstrated in three participants: one was a confirmation of the case that had proved H1N1 positive by RT-PCR; the others occurred in two asymptomatic participants belonging to the low- and high-risk groups. An influenza-like illness was assumed in four participants from the high- (n = 1), intermediate- (n = 1) and low-risk (n = 2) groups; these findings were not confirmed by positive results from either diagnostic test.

CONCLUSIONS

This study demonstrates a low incidence rate of influenza A (H1N1) infection among healthcare workers during the 2009 H1N1 pandemic in a setting with high hygiene standards.

Communicability of H1N1 and seasonal influenza among household contacts of cases in large families

Please cite this paper as: Mohamed et al. (2011) Communicability of H1N1 and seasonal influenza among household contacts of cases in large families. Influenza and Other Respiratory Viruses 6(3), e25–e29.

Background  Quantitative knowledge of the transmissibility of influenza is crucial to its prevention and control.

Objectives  To quantify the transmission of influenza A (H1N1) and seasonal influenza in household contacts of patients with influenza diagnosed in a large university hospital.

Patients/Methods  A prospective study was conducted between September and October 2009 in which all confirmed cases of influenza diagnosed at King Khalid University Hospital were included. All household contacts were followed by telephone calls every other day for 12 days. They were asked about the development of influenza symptoms in addition to their age and nationality.

Results  Overall, 432 household contacts of 69 influenza A (H1N1) cases and 417 contacts of 91 seasonal influenza cases were included. Suspected influenza was diagnosed in 16·9% and 14·4% of household contacts of H1N1 and seasonal influenza patients, respectively. Household reproduction numbers were 1·06 (0·84–1·28) for H1N1 and 0·66 (0·51–0·81) for seasonal influenza. Children in households were more susceptible than were adults (22·2% versus 13·7%, respectively). Evidence of coughing in the index case tripled the risk of infection in households afflicted with the H1N1 influenza [relative risk (RR) = 3·28, CI = 1·24–8·69], while evidence of a runny nose doubled it (RR = 1·89, CI = 1·19–2·92).

Conclusions  Communicability of influenza in households in Riyadh is comparable to that in other countries. Children are more susceptible to influenza infection. The presence of a cough or runny nose in the index cases increases the risk of infection.

Virus detection and duration of illness among patients with 2009 pandemic influenza A (H1N1) virus infection in Texas

Knowledge from early outbreaks is limited regarding the virus detection and illness duration of the 2009 pandemic influenza A (H1N1) infections. During the period from April to May 2009 in Texas, we collected serial nasopharyngeal (NP) and stool specimens from 35 participants, testing by real-time reverse transcriptase-polymerase chain reaction (rRT-PCR) and culture. The participants were aged 2 months to 71 years; 25 (71%) were under 18. The median duration of measured fever was 3.0 days and of virus detection in NP specimens was 4.2 days; however, few specimens were collected between days 5-9. The duration of virus detection (4.2 days) was similar to the duration of fever (3.5 days) (RR, 1.14; 95% CI, .66-1.95; P = .8), but was shorter than the duration of cough (11.0 days) (RR, .41; 95% CI, .24-.68; P < .001). We detected viral RNA in two participants' stools. All cultures were negative. This investigation suggests that the duration of virus detection was likely similar to the seasonal influenza virus.

Serial intervals and the temporal distribution of secondary infections within households of 2009 pandemic influenza A (H1N1): implications for influenza control recommendations

A critical issue during the 2009 influenza A (H1N1) pandemic was determining the appropriate duration of time individuals with influenza-like illness (ILI) should remain isolated to reduce onward transmission while limiting societal disruption. Ideally this is based on knowledge of the relative infectiousness of ill individuals at each point during the course of the infection. Data on 261 clinically apparent pH1N1 infector-infectee pairs in households, from 7 epidemiological studies conducted in the United States early in 2009, were analyzed to estimate the distribution of times from symptom onset in an infector to symptom onset in the household contacts they infect (mean, 2.9 days, not correcting for tertiary transmission). Only 5% of transmission events were estimated to take place >3 days after the onset of clinical symptoms among those ill with pH1N1 virus. These results will inform future recommendations on duration of isolation of individuals with ILI.

Viral shedding duration of pandemic influenza A H1N1 virus during an elementary school outbreak--Pennsylvania, May-June 2009

We report shedding duration of 2009 pandemic influenza A (pH1N1) virus from a school-associated outbreak in Pennsylvania during May through June 2009. Outbreak-associated students or household contacts with influenza-like illness (ILI) onset within 7 days of interview were recruited. Nasopharyngeal specimens, collected every 48 hours until 2 consecutive nonpositive tests, underwent real-time reverse transcriptase polymerase chain reaction (rRT-PCR) and culture for pH1N1 virus. Culture-positive specimens underwent virus titrations. Twenty-six (median age, 8 years) rRT-PCR-positive persons, for pH1N1 virus, were included in analysis. Median shedding duration from fever onset by rRT-PCR was 6 days (range, 1-13) and 5 days (range, 1-7) by culture. Following fever resolution virus was isolated for a median of 2 days (range, 0-5). Highest and lowest virus titers detected, 2 and 5 days following fever onset, were 3.2 and 1.2 log(10) TCID(50)/mL respectively. Overall, shedding duration in children and adults were similar to seasonal influenza viruses.

Contagious period for pandemic (H1N1) 2009

Most infected persons shed live virus after fever abated.

We estimated the proportion of persons with pandemic (H1N1) 2009 who were shedding infectious virus at diagnosis and on day 8 of illness. In households with confirmed cases, nasopharyngeal swabs were collected on all members and tested by PCR and virus culture. Of 47 cases confirmed by PCR at <7 days of illness, virus culture was positive in 92% (11/12) of febrile and 63% (22/35) of afebrile persons. Of 43 persons with PCR-confirmed pandemic (H1N1) 2009 from whom a second specimen was collected on day 8, 74% remained PCR positive and 19% were culture positive. If the 73 symptomatic household members without PCR-confirmed illness are assumed to have pandemic (H1N1) 2009, a minimum of 8% (6/73) of case-patients shed replicating virus on day 8. Self-isolation only until fever abates appears insufficient to limit transmission. Self-isolation for a week may be more effective, although some case-patients still would shed infectious virus.

Pandemic (H1N1) 2009 influenza in the UK: clinical and epidemiological findings from the first few hundred (FF100) cases

The UK was one of few European countries to document a substantial wave of pandemic (H1N1) 2009 influenza in summer 2009. The First Few Hundred (FF100) project ran from April-June 2009 gathering information on early laboratory-confirmed cases across the UK. In total, 392 confirmed cases were followed up. Children were predominantly affected (median age 15 years, IQR 10-27). Symptoms were mild and similar to seasonal influenza, with the exception of diarrhoea, which was reported by 27%. Eleven per cent of all cases had an underlying medical condition, similar to the general population. The majority (92%) were treated with antiviral drugs with 12% reporting adverse effects, mainly nausea and other gastrointestinal complaints. Duration of illness was significantly shorter when antivirals were given within 48 h of onset (median 5 vs. 9 days, P=0.01). No patients died, although 14 were hospitalized, of whom three required mechanical ventilation. The FF100 identified key clinical and epidemiological characteristics of infection with this novel virus in near real-time.

Predictors and outcomes of respiratory failure among hospitalized pneumonia patients with 2009 H1N1 influenza in Taiwan

OBJECTIVES

The worldwide outbreak of a pandemic influenza A (H1N1) virus began in April 2009. We characterized the clinical features of the hospitalized pneumonia patients with 2009 H1N1 influenza in Taiwan and elucidated the risk of those patients for developing respiratory failure.

METHODS

Severe complicated influenza infection is a notifiable disease in Taiwan and the hospitalized pneumonia patients with 2009 H1N1 influenza were reported accordingly. We reviewed the medical records of the eligible cases by September 8, 2009; development of respiratory failure was the primary endpoint.

RESULTS

Of the 96 patients we studied, 22 (23%) developed respiratory failure. Among those, 10 (45%) died and all of the non-respiratory failure patients survived. Age distribution, presence of dyspnea, lymphopenia, leukopenia, PaO(2)/FiO(2) ratio, PaCO(2), SOFA score, infiltration on chest x-ray at admission were different between two groups by univariate analysis. The clinical course was also different, with longer duration from onset of symptoms to use of oseltamivir, longer hospital stay, and more complications during hospitalization in patients with respiratory failure. A multivariate logistic regression showed an association between development of respiratory failure and SOFA score > or = 4 at admission, initial lymphocyte count < or = 800/microL, and the duration from symptom onset to initiation of oseltamivir > 48 h.

CONCLUSIONS

Respiratory failure in patients with 2009 H1N1 influenza leads to poor outcomes, including complications and death. Clinicians could apply the three predictors at admission to identify the high-risk pneumonic patients for developing respiratory failure. Further study is needed to validate the findings of this study in other settings.