Dataset Information

Transmissibility of seasonal and pandemic influenza in a cohort of households in Hong Kong in 2009.

ABSTRACT: The household secondary attack proportion (SAP) is commonly used to measure the transmissibility of an infectious disease.We analyzed the final outbreak size distributions of pandemic A(H1N1), seasonal A(H1N1), and A(H3N2) infections identified in paired sera collected from members of 117 Hong Kong households in April and in August-October 2009.The estimated community probability of infection overall was higher for children than adults; the probability was similar for pandemic A(H1N1) and seasonal A(H3N2) influenza. The household SAP for pandemic A(H1N1) was higher in children than in adults, whereas for seasonal A(H3N2), it was similar in children and adults. The estimated SAPs were similar for seasonal A(H3N2) and pandemic A(H1N1) after excluding persons with higher baseline antibody titers from analysis.Pandemic and seasonal influenza A viruses had similar age-specific transmissibility in a cohort of initially uninfected households, after adjustment for baseline immunity.

SUBMITTER: Klick B

PROVIDER: S-EPMC3206962 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature

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Transmissibility of seasonal and pandemic influenza in a cohort of households in Hong Kong in 2009.

Klick Brendan B Nishiura Hiroshi H Ng Sophia S Fang Vicky J VJ Leung Gabriel M GM Peiris J S Malik JS Cowling Benjamin J BJ

Epidemiology (Cambridge, Mass.) 20111101 6

<h4>Background</h4>The household secondary attack proportion (SAP) is commonly used to measure the transmissibility of an infectious disease.<h4>Methods</h4>We analyzed the final outbreak size distributions of pandemic A(H1N1), seasonal A(H1N1), and A(H3N2) infections identified in paired sera collected from members of 117 Hong Kong households in April and in August-October 2009.<h4>Results</h4>The estimated community probability of infection overall was higher for children than adults; the prob ...[more]

PMID: 21878814

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Project description:BACKGROUND:Serial cross-sectional data on antibody levels to the 2009 pandemic H1N1 influenza A virus from a population can be used to estimate the infection attack rates and immunity against future infection in the community. METHODS:From April through December 2009, we obtained 12,217 serum specimens from blood donors (aged 16-59 years), 2520 specimens from hospital outpatients (aged 5-59 years), and 917 specimens from subjects involved in a community pediatric cohort study (aged 5-14 years). We estimated infection attack rates by comparing the proportions of specimens with antibody titers ? 1:40 by viral microneutralization before and after the first wave of the pandemic. Estimates were validated using paired serum samples from 324 individuals that spanned the first wave. Combining these estimates with epidemiologic surveillance data, we calculated the proportion of infections that led to hospitalization, admission to the intensive care unit (ICU), and death. RESULTS:We found that 3.3% and 14% of persons aged 5-59 years had antibody titers ? 1:40 before and after the first wave, respectively. The overall attack rate was 10.7%, with age stratification as follows: 43.4% in persons aged 5-14 years, 15.8% in persons aged 15-19 years, 11.8% in persons aged 20-29 years, and 4%-4.6% in persons aged 30-59 years. Case-hospitalization rates were 0.47%-0.87% among persons aged 5-59 years. Case-ICU rates were 7.9 cases per 100,000 infections in persons aged 5-14 years and 75 cases per 100,000 infections in persons aged 50-59 years, respectively. Case-fatality rates were 0.4 cases per 100,000 infections in persons aged 5-14 years and 26.5 cases per 100,000 infections in persons aged 50-59 years, respectively. CONCLUSIONS:Almost half of all school-aged children in Hong Kong were infected during the first wave. Compared with school children aged 5-14 years, older adults aged 50-59 years had 9.5 and 66 times higher risks of ICU admission and death if infected, respectively.

Project description:Following the emergence of 2009 pandemic influenza A virus subtype H1N1 (A[H1N1]pdm09) in the United States and Mexico in April 2009, A(H1N1)pdm09 spread rapidly all over the world. There is a dearth of information about the epidemiology of A(H1N1)pdm09 in Africa, including Morocco. We describe the epidemiologic characteristics of the A(H1N1)pdm09 epidemic in Morocco during 2009-2010, including transmissibility and risk factors associated with fatal disease.We implemented influenza surveillance for patients presenting with influenza-like illness (ILI) at 136 private and public clinics for patients with severe acute respiratory illness (SARI) at 16 regional public hospitals from June 2009 through February 2010. Respiratory samples and structured questionnaires were collected from all enrolled patients, and samples were tested by real-time reverse-transcription polymerase chain reaction for influenza viruses. We estimated the risk factors associated with fatal disease as well as the basic reproduction number (R(0)) and the serial interval of the pandemic virus.From June 2009 through February 2010, we obtained 3937 specimens, of which 1452 tested positive for influenza virus. Of these, 1398 (96%) were A(H1N1)pdm09. Forty percent of specimens from ILI cases (1056 of 2646) and 27% from SARI cases (342 of 1291) were positive for A(H1N1)pdm09. Sixty-four deaths occurred among laboratory-confirmed A(H1N1)pdm09 SARI cases. Among these cases, those who had hypertension (age-adjusted odd ratio [aOR], 28.2; 95% confidence interval [CI], 2.0-398.7), had neurological disorders (aOR, 7.5; 95% CI, 1.5-36.4), or were obese (aOR, 7.1; 95% CI, 1.6-31.1), as well as women of gestational age who were pregnant (aOR, 2.5; 95% CI, 1.1-5.6), were at increased risk of death. Across the country, elevated numbers of locally acquired infections were detected 4 months after the detection of the first laboratory-confirmed case and coincided with the expected influenza season (October-January) in Morocco. We obtained an R(0) estimate of 1.44 (95% CI, 1.32-1.56) and a mean serial interval (±SD) of 2.3 ± 1.4 days (95% CI, 1.6-3.0).Widespread but delayed community transmission of A(H1N1)pdm09 occurred in Morocco in 2009, and A(H1N1)pdm09 became the dominant influenza virus subtype during the 2009-2010 influenza season. The transmissibility characteristics were similar to those observed in other countries.

Dataset Information

Transmissibility of seasonal and pandemic influenza in a cohort of households in Hong Kong in 2009.

Publications

Transmissibility of seasonal and pandemic influenza in a cohort of households in Hong Kong in 2009.

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