News

1. Update on oseltamivir resistant pandemic A (H1N1) 2009 influenza virus: January 2010, Weekly epidemiological record
5 February 2010, 85th year; No. 6, 2010, 85, 37–48

The number of reported cases of oseltamivir-resistant pandemic A(H1N1) 2009 influenza virus infection remains low despite the large scale of the pandemic, widespread use of oseltamivir and extensive monitoring of susceptibility. Although there is no evidence of general community circulation of such resistant viruses, there is clear evidence of limited person-to-person transmission in several epidemiological settings. Active surveillance for antiviral resistance in pandemic A(H1N1) 2009 virus needs to be maintained by clinicians, laboratories and agencies. All cases of oseltamivir-resistant pandemic A (H1N1) 2009 influenza virus infection should be investigated and promptly notified to relevant agencies including WHO.

Selected Scientific Publications:

1. Vaccination against pandemic influenza A/H1N1v in England: A real-time economic evaluation, Baguelin, M., A. J. V. Hoek, et al.
Vaccine In Press, Corrected Proof.

The authors of this study present a real-time assessment of the effectiveness and cost-effectiveness of alternative influenza A(H1N1) vaccination strategies. A transmission dynamic model was fitted to the estimated number of cases in real-time and used to generate plausible autumn scenarios under different vaccination options. The proportion of these cases by age and risk group leading to primary care consultations, National Pandemic Flu Service consultations, emergency attendances, hospitalisations, intensive care and death was then estimated using existing data from the pandemic. Vaccination of the high-risk groups is estimated to prevent about 45 deaths and save around 2900 QALYs. Extending vaccination to low-risk individuals is expected to result in more modest gains in deaths and QALYs averted. Extending vaccination to school-age children would be the most cost-effective extension. Certain groups appear to be at significantly higher risk of complications and deaths, and so it appears both effective and cost-effective to vaccinate them.

2. 2009 H1N1 Influenza A and Pregnancy Outcomes in Victoria, Australia, Saliya Hewagama, Sue P. Walker, Rhonda L. Stuart, Claire Gordon, Paul D. R. Johnson, N. Deborah Friedman, Mary O’Reilly, Allen C. Cheng, and Michelle L. Giles
Clinical Infectious Diseases 1 March 2010, Vol. 50, No. 5: 686-690.

The case series described in this scientific work confirms a high number of complications in pregnant women due to the 2009 influenza A(H1N1) pandemic. Many of these women had co-morbidities, although almost 50% of the women in this case series that required hospitalization did not have an additional risk factor other than being pregnant. Pregnant women are at high risk of complications following infection with pandemic 2009 A(H1N1) influenza. In this case series of 43 pregnant women, the estimated incidence of hospitalization for women in their third trimester of pregnancy was 0.46%. Of the 36% of women who gave birth during their hospitalization, 40% delivered preterm.

3. Effects of Oseltamivir Treatment on Duration of Clinical Illness and Viral Shedding and Household Transmission of Influenza Virus, Sophia Ng, Benjamin J. Cowling, Vicky J. Fang, Kwok Hung Chan, Dennis K. M. Ip, Calvin K. Y. Cheng, Timothy M. Uyeki, Peter M. Houck, J. S. Malik Peiris, and Gabriel M. Leung
Clinical Infectious Diseases 1 March 2010, Vol. 50, No. 5: 707-714.

The authors of this study recruited index outpatients whose rapid test results were positive for influenza from February through September 2007 and January through September 2008. Household contacts were followed up for 7–10 days during 3–4 home visits to monitor symptoms. Index patients who took oseltamivir within 24 h of symptom onset halved the time to symptom alleviation. Oseltamivir treatment was not associated with statistically significant reduction in the duration of viral shedding. Household contacts of index patients who had taken oseltamivir within 24 h of onset had a non-statistically significant lower risk of developing laboratory‐confirmed infection and a marginally statistically significant lower risk of clinical illness compared with contacts of index patients who did not take oseltamivir. Summarising, oseltamivir treatment was effective in reducing the duration of symptoms but evidence of household reduction in transmission of influenza virus was inconclusive.

4. Pandemic (H1N1) 2009 risk for nurses after trivalent vaccination, Loeb M, Earn DJD, Smieja M, Webby R
Emerg Infect Dis. 2010 Apr; [Epub ahead of print]

This letter reports results of the effect of inactivated seasonal influenza vaccination on risk of pandemic A(H1N1) 2009 in a cohort of nurses in Canada who participated in a recent randomized controlled trial that compared the effectiveness of surgical masks with that of N95 respirators in preventing influenza. A total of 446 nurses from 8 hospitals in the province of Ontario were enrolled in the trial. They were then randomly assigned an intervention; 225 were assigned to wear surgical masks, and 221 were assigned to wear the N95 respirator. A total of 128 (30.3%) received the trivalent influenza vaccine - vaccination status being similar between the groups. Of 128 nurses who received the trivalent influenza vaccine, 9 (7.0%) showed seroconversion versus 33 (11.2%) of those that did not received the trivalent influenza vaccine.
The authors concluded that these data suggest a possible positive effect of seasonal influenza vaccine reducing risk of infection with pandemic A(H1N1) 2009 but the confidence interval around the point estimate of the effect overlapped 1.0 (relative risk 0.63, 95% confidence interval 0.31–1.27, p = 0.19) so one cannot exclude the possibility of no vaccine effect.

5. Estimating the impact of the 2009 influenza A(H1N1) pandemic on mortality in the elderly in Navarre, Spain, Castilla J, Etxeberria J, Ardanaz E, Floristán Y, López Escudero R, Guevara M.
Euro Surveill. 2010;15(5):pii=19481.

This study presents the analysis of mortality among people aged 65 years or older in the autonomous region of Navarra, Spain, in 2009 and compared it with the mean for the same period of time in the previous three years. In the pandemic weeks 24 to 52 of 2009 the authors of the study observed 4.9% more deaths than expected. Excess mortality occurred during the circulation of seasonal influenza and the first wave of pandemic influenza. In the second wave of pandemic influenza there was a non-significant excess of deaths. Surveillance of laboratory-confirmed severe influenza cases detected only one death in this age group.

6. Higher all-cause mortality in children during autumn 2009 compared with the three previous years: pooled results from eight European countries, Mazick A, Gergonne B, Wuillaume F, et al.
Euro Surveill. 2010;15(5):pii=19480

This work describes weekly fluctuations of all-cause mortality observed in eight European countries during the period between week 27 and 51of 2009, in comparison with three previous years. With some limitations in mind, the preliminary data indicate that there was no major excess of deaths during the 2009 influenza pandemic in the participating countries. Compared with excess mortality of the three previous years the mortality observed during the autumn wave of the 2009 pandemic did not reach levels normally seen during seasonal influenza epidemics when mainly senior citizens die. However, there was excess mortality in the 5-14-year-olds compared with excess levels of the previous three years. This work reports findings of a similar pattern in children 0-4 years of age with an excess of almost the same magnitude as the older children. Further research is necessary to disentangle the mortality pattern among children, in particular in light of the pandemic.

7. High frequency of cross-reacting antibodies against 2009 pandemic influenza A(H1N1) virus among the elderly in Finland
Ikonen N, Strengell M, Kinnunen L, Österlund P, Pirhonen J, Broman M, Davidkin I, Ziegler T, Julkunen I, Euro Surveill. 2010;15(5):pii=19478.

Approximately 1,000 serum specimens collected in Finland in 2004 and 2005 from individuals born between 1909 and 2005, were analysed by haemagglutination-inhibition test for the presence of antibodies against the 2009 pandemic influenza A(H1N1) and recently circulating seasonal influenza A viruses. Ninety-six per cent of individuals born between 1909 and 1919 had antibodies against the 2009 pandemic influenza virus, while in age groups born between 1920 and 1944, the prevalence varied from 77% to 14%. Most individuals born after 1944 lacked antibodies to the pandemic virus. In sequence comparisons the haemagglutinin (HA) gene of the 2009 pandemic influenza A(H1N1) virus was closely related to that of the Spanish influenza and 1976 swine influenza viruses. Based on the three-dimensional structure of the HA molecule, the antigenic epitopes of the pandemic virus HA are more closely related to those of the Spanish influenza HA than to those of recent seasonal influenza A(H1N1) viruses. Among the elderly, cross-reactive antibodies against the 2009 pandemic influenza virus, which likely originate from infections caused by the Spanish influenza virus and its immediate descendants, may provide protective immunity against the present pandemic virus.