Influenza surveillance in Europe: establishing epidemic thresholds by the Moving Epidemic Method

Please cite this paper as: Vega et al. (2012) Influenza surveillance in Europe: establishing epidemic thresholds by the moving epidemic method. Influenza and Other Respiratory Viruses 7(4), 546–558. Background Timely influenza surveillance is important to monitor influenza epidemics. Objectives (i) To calculate the epidemic threshold for influenza‐like illness (ILI) and acute respiratory infections (ARI) in 19 countries, as well as the thresholds for different levels of intensity. (ii) To evaluate the performance of these thresholds. Methods The moving epidemic method (MEM) has been developed to determine the baseline influenza activity and an epidemic threshold. False alerts, detection lags and timeliness of the detection of epidemics were calculated. The performance was evaluated using a cross‐validation procedure. Results The overall sensitivity of the MEM threshold was 71·8% and the specificity was 95·5%. The median of the timeliness was 1 week (range: 0–4·5). Conclusions The method produced a robust and specific signal to detect influenza epidemics. The good balance between the sensitivity and specificity of the epidemic threshold to detect seasonal epidemics and avoid false alerts has advantages for public health purposes. This method may serve as standard to define the start of the annual influenza epidemic in countries in Europe.     

Hospitalization of influenza‐like illness patients recommended by general practitioners in France between 1997 and 2010

Please cite this paper as: Pelat et al. (2012) Hospitalization of influenza‐like illness patients recommended by general practitioners in France between 1997 and 2010. Influenza and Other Respiratory Viruses DOI: 10.1111/j.1750‐2659.2012.00356.x. Background The case–hospitalization ratio (CHR) is a key quantity for the management of emerging pathogens such as pandemic influenza. Yet, few running surveillance systems prospectively monitor the CHR during influenza epidemics. Here, we analyze the proportion of recommended hospitalizations (PRH) among influenza‐like illness (ILI) patients attended in general practice in France and compare the PRH observed during the 2009–2010 A(H1N1) pandemic with the one of the twelve previous seasons. Methods ILI cases were recorded by general practitioners (GPs) involved in surveillance, who indicated for each case whether they recommended hospitalization. We stratify the analysis by age, sex, and viral subtype. We investigate the reasons why GPs recommended hospitalization and the presence of risk factors for pandemic A(H1N1) complications. Results The average PRH over the seasons 1997–1998 to 2008–2009 was 3·4‰ (3–3·9). It was three times higher during the 2009–2010 pandemic than during seasonal influenza epidemics (OR = 2·89, 95% CI: 2·28–3·64). The highest increase was among 20–39‐year‐old women: OR = 11·8 (5·04–29·59). Overall, the principal reasons for recommending hospitalization were “respiratory problems” and “bad general condition.” However, during the pandemic, “age” (mainly associated with infants), “pregnancy,” and “diagnostic” became more frequent than before (P < 0·001). Finally, pregnancy was the reported risk factor for pandemic A(H1N1) complications that had the largest impact on hospitalization recommendation during the pandemic (OR = 38·62, P < 0·001). Conclusion Easily implemented in surveillance systems, this protocol has the potential to reveal changes in hospitalization recommendation by GPs. Moreover, if the right data are collected alongside, it could give timely insights into epidemic severity.     

Attempted early detection of influenza A (H1N1) pandemic with surveillance data of influenza-like illness and unexplained pneumonia

Please cite this paper as: Qian et al. (2011) Attempted early detection of influenza A (H1N1) pandemic with surveillance data of influenza‐like illness and unexplained pneumonia. Influenza and Other Respiratory Viruses 5(6), e479–e486. Background To collect disease information and provide data for early detection of epidemics, two surveillance systems were established for influenza‐like illness (ILI) and unexplained pneumonia (UP) in Wuxi, People’s Republic of China. Objectives The current study aims to describe the performance of these surveillance systems during 2004–2009 and to evaluate the value of surveillance data in detection of influenza epidemics. Methods Two national ILI sentinel hospitals and three UP sentinel hospitals provided data to the surveillance systems. The surveillance data from hospital‐based outpatient clinics and emergency rooms were compared by year. The ILI data of 2009 were further modeled based on previous data using both a control chart method and a moving average regression method. Alarms of potential epidemics would be raised when the input surveillance data surpassed a threshold. Results In 2009, the proportions of ILI and respiratory illness with fever (one surveillance syndrome of the UP system) to total patient visits (3·40% and 11·76%, respectively) were higher than the previous years. The surveillance data of both systems also showed developing trends similar to the influenza A (H1N1) pandemic in 2009. When the surveillance data of 2009 were fitted in the two detection models, alarms were produced on the occurrence of the first local case of influenza A (H1N1), outbreaks in schools and in general populations. Conclusions The results indicated the potential for using ILI and UP surveillance data as syndromic indicators to detect and provide an early warning for influenza epidemics.     

Virus detection and its association with symptoms during influenza‐like illness in a sample of healthy adults enrolled in a randomised controlled vaccine trial

Background Viral respiratory infections are associated with significant morbidity and mortality. Many new aetiological agents have been described recently. Objectives We looked for respiratory viruses in a population‐based sample of healthy adults with influenza‐like illness (ILI). We investigated host and spatio‐temporal associations with virus isolation and host, spatio‐temporal and virus associations with self‐reported symptoms. Patients/Methods We recruited 586 participants experiencing 651 illness episodes from a population of healthy adults enrolled in an influenza vaccine effectiveness trial. At ILI assessment visits, a respiratory swab was collected and tested for viruses using a combination of polymerase chain reaction (PCR) assays. Participants also completed a questionnaire detailing their clinical course in 336 episodes. Results Of 643 samples analysed, a virus was identified in 44%. Half were picornaviruses, with influenza and coronaviruses the next most common. Individuals with influenza were significantly less likely to have been immunised than the reference (virus negative) population (OR = 0·52 (0·31, 0·87) P = 0·01). The mean symptom score (95% CI) reported by individuals with influenza was significantly higher than in all other episodes [Influenza: 10·2 (9·4, 10·9); Other: 7·4 (7·2, 7·7); Difference (95% CI): 2·5 (1·5, 3·5); P < 0·001]. In an analysis restricted to influenza‐positive cases, the symptom score was not attenuated by vaccination. Conclusions Our findings indicate that a greater number of symptoms are displayed by individuals presenting with influenza confirmed ILI compared with other agents that cause ILI. While influenza vaccination reduced the probability of influenza virus detection, symptom score for influenza‐positive ILI was not attenuated.     

Findings from a household randomized controlled trial of hand washing and face masks to reduce influenza transmission in Bangkok, Thailand

Please cite this paper as: Simmerman et al. (2011) Findings from a household randomized controlled trial of hand washing and face masks to reduce influenza transmission in Bangkok, Thailand. Influenza and Other Respiratory Viruses 5(4), 256–267 Background Evidence is needed on the effectiveness of non‐pharmaceutical interventions (NPIs) to reduce influenza transmission. Methodology We studied NPIs in households with a febrile, influenza‐positive child. Households were randomized to control, hand washing (HW), or hand washing plus paper surgical face masks (HW + FM) arms. Study nurses conducted home visits within 24 hours of enrollment and on days 3, 7, and 21. Respiratory swabs and serum were collected from all household members and tested for influenza by RT‐PCR or serology. Principal Findings Between April 2008 and August 2009, 991 (16·5%) of 5995 pediatric influenza‐like illness patients tested influenza positive. Four hundred and forty‐two index children with 1147 household members were enrolled, and 221 (50·0%) were aged <6 years. Three hundred and ninety‐seven (89·8%) households reported that the index patient slept in the parents’ bedroom. The secondary attack rate was 21·5%, and 56/345 (16·3%; 95% CI 12·4–20·2%) secondary cases were asymptomatic. Hand‐washing subjects reported 4·7 washing episodes/day, compared to 4·9 times/day in the HW + FM arm and 3·9 times/day in controls (P = 0·001). The odds ratios (ORs) for secondary influenza infection were not significantly different in the HW arm (OR = 1·20; 95% CI 0·76–1·88; P‐0.442), or the HW + FM arm (OR = 1·16; 95% CI .0·74–1·82; P = 0.525). Conclusions Influenza transmission was not reduced by interventions to promote hand washing and face mask use. This may be attributable to transmission that occurred before the intervention, poor facemask compliance, little difference in hand‐washing frequency between study groups, and shared sleeping arrangements. A prospective study design and a careful analysis of sociocultural factors could improve future NPI studies.     

The impact of bacterial and viral co‐infection in severe influenza

Please cite this paper as: Blyth et al. (2013) The impact of bacterial and viral co‐infection in severe influenza. Influenza and Other Respiratory Viruses 7(2) 168–176. Background Many questions remain concerning the burden, risk factors and impact of bacterial and viral co‐infection in patients with pandemic influenza admitted to the intensive care unit (ICU). Objectives To examine the burden, risk factors and impact of bacterial and viral co‐infection in Australian patients with severe influenza. Patients/Methods A cohort study conducted in 14 ICUs was performed. Patients with proven influenza A during the 2009 influenza season were eligible for inclusion. Demographics, risk factors, clinical data, microbiological data, complications and outcomes were collected. Polymerase chain reaction for additional bacterial and viral respiratory pathogens was performed on stored respiratory samples. Results Co‐infection was identified in 23·3–26·9% of patients with severe influenza A infection: viral co‐infection, 3·2–3·4% and bacterial co‐infection, 20·5–24·7%. Staphylococcus aureus was the most frequent bacterial co‐infection followed by Streptococcus pneumoniae and Haemophilus influenzae. Patients with co‐infection were younger [mean difference in age = 8·46 years (95% CI: 0·18–16·74 years)], less likely to have significant co‐morbidities (32·0% versus 66·2%, P = 0·004) and less frequently obese [mean difference in body mass index = 6·86 (95% CI: 1·77–11·96)] compared to those without co‐infection. Conclusions Bacterial or viral co‐infection complicated one in four patients admitted to ICU with severe influenza A infection. Despite the co‐infected patients being younger and with fewer co‐morbidities, no significant difference in outcomes was observed. It is likely that co‐infection contributed to a need for ICU admission in those without other risk factors for severe influenza disease. Empiric antibiotics with staphylococcal activity should be strongly considered in all patients with severe influenza A infection.     

厄尔尼诺-南方涛动现象与流行性感冒联系的系统评价

目的调查分析既往及正在执行的厄尔尼诺-南方涛动现象(El Ni1o-Southern Oscillation,ENSO)与流行性感冒关联的相关研究,并评价ENSO对流行性感冒相关指标(如流感流行高峰的出现时间、流感样病例报告人数等)的影响,为进一步开展天气及气象因素影响流感病毒传播研究提供依据和建议。方法计算机检索MEDLINE,EMBASE,Science Direct,HEED、中国生物医学文献数据库(CBMdisc)、万方学位论文全文数据库,查找1988~2016年10月已发表的关于ENSO与流行性感冒联系的文献,并运用循证医学方法进行文献数据提取和分析。结果共检索到78篇文献,其中符合纳入标准的已发表文献10篇。二次文献研究显示,出现ENSO与流感大流行的发生,流感高峰的出现时间,流感样病例就诊数及重症死亡数都有较大关联,且El Ni1o和La Ni1a现象对流感相关指标的影响也不尽相同。结论从纳入研究的已发表文献分析结果来看,ENSO与流行性感冒相关指标之间有较强的相关性。     

Epidemiological isolation causing variable mortality in Island populations during the 1918-1920 influenza pandemic

Please cite this paper as: Shanks et al. (2012) Epidemiological isolation causing variable mortality in Island populations during the 1918–1920 influenza pandemic. Influenza and Other Respiratory Viruses 6(6), 417–423. Background During the 1918 pandemic period, influenza‐related mortality increased worldwide; however, mortality rates varied widely across locations and demographic subgroups. Islands are isolated epidemiological situations that may elucidate why influenza pandemic mortality rates were so variable in apparently similar populations. Objectives Our objectives were to determine and compare the patterns of pandemic influenza mortality on islands. Methods We reviewed historical records of mortality associated with the 1918–1920 influenza pandemic in various military and civilian groups on islands. Results and Conclusions Mortality differed more than 50‐fold during pandemic‐related epidemics on Pacific islands [range: 0·4% (Hawaii) to 22% (Samoa)], and on some islands, mortality sharply varied among demographic subgroups of island residents such as Saipan: Chamorros [12%] and Caroline Islanders [0·4%]. Among soldiers from island populations who had completed initial military training, influenza‐related mortality rates were generally low, for example, Puerto Rico (0·7%) and French Polynesia (0·13%). The findings suggest that among island residents, those who had been exposed to multiple, antigenically diverse respiratory pathogens prior to infection with the 1918 pandemic strain (e.g., less isolated) experienced lower mortality. The continuous circulation of antigenically diverse influenza viruses and other respiratory infectious agents makes widespread high mortality during future influenza pandemics unlikely.     

Epidemiology of seasonal influenza in the Middle East and North Africa regions, 2010‐2016: Circulating influenza A and B viruses and spatial timing of epidemics

Background

There is a limited knowledge regarding the epidemiology of influenza in Middle East and North Africa.

Objectives

We described the patterns of influenza circulation and the timing of seasonal epidemics in countries of Middle East and North Africa.

Methods

We used virological surveillance data for 2010‐2016 from the WHO FluNet database. In each country, we calculated the median proportion of cases that were caused by each virus type and subtype; determined the timing and amplitude of the primary and secondary peaks; and used linear regression models to test for spatial trends in the timing of epidemics.

Results

We included 70 532 influenza cases from seventeen countries. Influenza A and B accounted for a median 76.5% and 23.5% of cases in a season and were the dominant type in 86.8% and 13.2% of seasons. The proportion of influenza A cases that were subtyped was 85.9%, while only 4.4% of influenza B cases were characterized. For most countries, influenza seasonality was similar to the Northern Hemisphere, with a single large peak between January and March; exceptions were the countries in the Arabian Peninsula and Jordan, all of which showed clear secondary peaks, and some countries had an earlier primary peak (in November‐December in Bahrain and Qatar). The direction of the timing of influenza activity was east to west and south to north in 2012‐2013 and 2015‐2016, and west to east in 2014‐2015.

Conclusions

The epidemiology of influenza is generally uniform in countries of Middle East and North Africa, with influenza B playing an important role in the seasonal disease burden.     

Multisite virological influenza surveillance in India: 2004-2008

Please cite this paper as: Chadha et al. (2011) Multi site Virological Influenza Surveillance in India: 2004–2008. Influenza and Other Respiratory Viruses 6(3), 196–203. Background Influenza surveillance is important to identify circulating, emerging/reemerging strains and unusual epidemiological trends. With these objectives, a multisite human influenza surveillance network was initiated in India in 2004. Methods Epidemiologic data and throat swabs for laboratory testing were collected from patients with influenza‐like illness (ILI) and severe acute respiratory infections (SARI). Virus isolation was carried out in Madin–Darby canine kidney cells and strains identified by hemagglutination inhibition assay. Meteorological data were collected. Results From September 2004 to December 2008, 617 (4·43%) of 13928 cases yielded isolates: 27·8% were influenza A(H1N1), 29·8% were type A(H3N2), and 42·3% were type B. The yearly type and subtype distribution varied significantly from site to site. Peak influenza activity was observed from June to August in Delhi, Pune, and Kolkata and October to December in Chennai. Maximum influenza activity was seen during the rains in Delhi, Pune, Chennai, and Kolkata in correlation with virus isolations. Multivariate analysis of ILI cases showed chill/rigors, cough, fatigue, and ILI in family, correlated positively with isolation. Genetic analysis of Indian isolates revealed that viruses matched with vaccine strains by and large. Overlapping between circulating and vaccine component strains of consecutive years was also observed. Conclusions Seasonal influenza A(H1N1), H3N2, and type B co‐circulated in all regions without any particular pattern of movement of any subtype. Year‐round limited influenza activity with peaks during rains was observed. Genetic drifts and varying seasonality in different parts of the country suggest that a staggered timing of vaccination may be appropriate for India.     

Global patterns of seasonal influenza activity,duration of activity and virus (sub)type circulation from 2010 to 2020

BackgroundSeasonal influenza viruses undergo unpredictable changes, which may lead to antigenic mismatch between circulating and vaccine strains and to a reduced vaccine effectiveness. A continuously updated knowledge of influenza strain circulation and seasonality is essential to optimize the effectiveness of influenza vaccination campaigns. We described the global epidemiology of influenza between the 2009 A(H1N1)p and the 2020 COVID‐19 pandemic.MethodsInfluenza virological surveillance data were obtained from the WHO‐FluNet database. We determined the median proportion of influenza cases caused by the different influenza virus types, subtypes, and lineages; the typical timing of the epidemic peak; and the median duration of influenza epidemics (applying the annual average percentage method with a 75% threshold).ResultsWe included over 4.6 million influenza cases from 149 countries. The median proportion of influenza cases caused by type A viruses was 75.5%, highest in the Southern hemisphere (81.6%) and lowest in the intertropical belt (73.0%), and ranged across seasons between 60.9% in 2017 and 88.7% in 2018. Epidemic peaks typically occurred during winter months in Northern and Southern hemisphere countries, while much more variability emerged in tropical countries. Influenza epidemics lasted a median of 25 weeks (range 8–42) in countries lying between 30°N and 26°S, and a median of 9 weeks (range 5–25) in countries outside this latitude range.ConclusionsThis work will establish an important baseline to better understand factors that influence seasonal influenza dynamics and how COVID‐19 may have affected seasonal activity and influenza virus types, subtypes, and lineages circulation patterns.     

Serological evidence of swine influenza in Brazil

Please cite this paper as: Rajão et al. (2013). Serological evidence of swine influenza in Brazil. Influenza and Other Respiratory Viruses 7(2), 109–112. The aim of this work was to detect serum antibodies specific to influenza viruses in swine in Brazil. Serum samples of 355 pigs from 17 herds in Minas Gerais state were tested by hemagglutination inhibition (HI) for antibodies against H1N1 swine (SIV) and human influenza viruses, and H3N2 SIV. HI revealed that 158 animals (44·5%) and 11 herds (64·7%) were positive for H1N1 SIV, 36 animals (10·1%) and four herds (23·5%) were positive for H3N2 SIV, and 136 animals (38·3%) and 10 herds (58·8%) were positive for H1N1 human. This study indicates that swine influenza is disseminated throughout Minas Gerais state, Brazil.     

Single‐dose inhaled laninamivir: registered in Japan and its potential role in control of influenza epidemics

Please cite this paper as: Sunagawa et al. (2012) Single‐dose inhaled laninamivir: registered in Japan and its potential role in control of influenza epidemics. Influenza and Other Respiratory Viruses DOI: 10.1111/j.1750‐2659.2012.00351.x.     

Low but highly variable mortality among nurses and physicians during the influenza pandemic of 1918-1919

Please cite this paper as: Shanks et al. (2011) Low but highly variable mortality among nurses and physicians during the influenza pandemic of 1918–1919. Influenza and Other Respiratory Viruses DOI: 10.1111/j.1750‐2659.2010.00195.x. Background During the 1918–1919 influenza pandemic, nurses and physicians were intensively exposed to the pandemic A/H1N1 strain. There are few published summaries of the mortality experiences of nurses and physicians during the pandemic. Methods Mortality records from U.S. and British Armies during the First World War and obituary notices in national medical association journals were reviewed to ascertain death notices of nurses and physicians likely to have died of influenza. Results Illness‐related mortality among U.S. military nurses (1·05%) was one and one‐half times higher than among U.S. medical officers (0·68%), nearly two times higher than among British medical officers (0·55%), and nine times higher than among British nurses (0·12%). Among U.S. nursing officers, mortality was approximately twice as high among those assigned in the United States than in Europe. Among civilian physicians, mortality during the influenza pandemic was markedly increased in Canada, New Zealand, South Africa and the United States but not Australia. Conclusions During the 1918 pandemic, mortality among nurses and physicians was relatively low compared to their patients and significantly varied across locations and settings. Medical‐care providers (particularly U.S. nursing officers) who were new to their assignments when pandemic‐related epidemics occurred may have had higher risk of influenza‐related mortality because of occupational exposures to bacterial respiratory pathogens that they had not previously encountered.     

Surveillance of Influenza in Indonesia, 2003–2007

Background Longitudinal data are limited about the circulating strains of influenza viruses and their public health impact in Indonesia. We conducted influenza surveillance among outpatients and hospitalized patients with influenza‐like illness (ILI) across the Indonesian archipelago from 2003 through 2007. Methodology Demographic, clinical data, and respiratory specimens were collected for 4236 ILI patients tested for influenza virus infection by RT‐PCR and viral culture. Principal Findings Influenza A and B viruses co‐circulated year‐round with seasonal peaks in influenza A virus activity during the rainy season (December–January). During 2003–2007, influenza viruses were identified in 20·1% (4236/21 030) of ILI patients, including 20·1% (4015/20 012) of outpatients, and 21·7% (221/1018) of inpatients. One H5N1 case was identified retrospectively in an outpatient with ILI. Antigenic drift in circulating influenza A and B virus strains was detected during the surveillance period in Indonesia. In a few instances, antigenically drifted viruses similar to the World Health Organization (WHO) vaccine strains were detected earlier than the date of their designation by WHO. Conclusions Influenza A and B virus infections are an important cause of influenza‐like illness among outpatients and hospitalized patients in Indonesia. While year‐round circulation of influenza viruses occurs, prevention and control strategies should be focused upon the seasonal peak during rainy season months. Ongoing virologic surveillance and influenza disease burden studies in Indonesia are important priorities to better understand the public health impact of influenza in South‐East Asia and the implications of influenza viral evolution and global spread.     

Unemployment and widespread influenza in America, 1999-2010

Please cite this paper as: Cornwell B. (2012) Unemployment and widespread influenza in America, 1999–2010. Influenza and Other Respiratory Viruses 6(1), 63–70. Background Research shows that unemployment reduces access to health care and vaccines and increases financial difficulty, family conflict, and other sources of stress that are known to suppress immune function. In addition, seasonal unemployment rates parallel seasonal influenza activity. Following a theory that argues that macroeconomic conditions affect population health, this paper examines whether there is an association between monthly unemployment rates and influenza activity. Methods Data from influenza activity surveillance reports from the Centers for Disease Control and Prevention are combined with information from the Bureau of Labor Statistics on state‐level unemployment rates in the U.S. for the flu seasons between 1999 and 2010. Pooled time‐series cross‐section logistic regression analyses are conducted to examine the effect of the unemployment rate on the likelihood of widespread and/or regional influenza activity in the 48 contiguous states throughout this period. A total of 3712 state‐month observations are examined. Results Net of other factors included in the multivariate regression analysis, a one‐percentage‐point increment in the unemployment rate is associated with between a 7·1% and 37·0% increment in the odds of widespread influenza (Odds ratio = 1·21). Likewise, a one‐percentage‐point increment in the unemployment rate is associated with between a 17·1% and 44·7% increment in the odds of at least regional influenza (Odds ratio = 1·30). Results hold regardless of whether time‐varying state‐level characteristics are included. Conclusions Higher state‐level unemployment increases the likelihood of regional and widespread influenza activity.     

Risk factors and effectiveness of preventive measures against influenza in the community

Please cite this paper as: Castilla et al. (2013) Risk factors and effectiveness of preventive measures against influenza in the community. Influenza and Other Respiratory Viruses 7(2) 177–183. Background  The role of different risk exposures and preventive measures against influenza has not been well established. Objective  The aim of this study was to evaluate risk factors and measures to prevent influenza infection in the community. Methods  We conducted a multicenter case–control study. Cases were 481 outpatients aged 18 years or older with laboratory‐confirmed influenza A(H1N1)09 in the 2009–2010 season in Spain. A control was selected for each case from outpatients from the same area matched by age and date of consultation. Information on risk situations, preventive measures and other variables was obtained by interview and review of the medical record. Results  In the multivariate conditional logistic regression analysis, the risk of a diagnosis of influenza increased with the number of cohabitants (compared with <3 cohabitants, three cohabitants had an OR = 1·80, 95% CI 1·12–2·89, and ≥5 cohabitants had an OR = 2·66, 95% CI 1·31–5·41) and for health care workers (OR = 2·94, 95% CI 1·53–5·66). The use of metropolitan public transport was associated with a lower frequency of a diagnosis of influenza (OR = 0·45, 95% CI 0·30–0·68) but not the use of taxis or long‐distance transport. The influenza A(H1N1)09 vaccine had a protective effect (OR = 0·13, 95% CI 0·04–0·48), unlike hand washing after touching contaminated surfaces or the use of alcohol‐based hand sanitizers. Conclusion  The home environment appears to play an important role in the spread of influenza in adults, but not the use of public transport. Health care workers have a higher risk of contracting influenza. Vaccination was the most effective preventive measure.     

Cigarette smoking as a risk factor for influenza‐associated mortality: evidence from an elderly cohort

Please cite this paper as: Wong et al. (2012) Cigarette smoking as a risk factor for influenza‐associated mortality: evidence from an elderly cohort. Influenza and Other Respiratory Viruses 7(4), 531–539. Background The effects of individual lifestyle factors on the mortality risk after influenza infection have not been explored. Objectives In this study, we assessed the modifying effects of cigarette smoking on mortality risks associated with influenza in a cohort of Hong Kong elders with a follow‐up period of 1998–2009. Methods We used the Cox proportional hazards model with time‐dependent covariates of weekly proportions of specimens positive for influenza (termed as influenza virus activity), to calculate the hazard ratio of mortality associated with a 10% increase in influenza virus activity for never, ex‐ and current smokers. Other individual lifestyle and socioeconomic factors as well as seasonal confounders were also added into the models. Results The overall hazard ratio associated with influenza was 1·028 (95% confidence interval, 1·006, 1·051) for all natural cause mortality and 1·035 (1·003, 1·068) for cardiovascular and respiratory mortality. We found that influenza‐associated hazard ratio was greater in current and ex‐smokers than in never smokers for mortality of all natural causes, cardiovascular and respiratory diseases. Conclusions The findings suggest that smoking might increase influenza‐associated mortality risks among elders.