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Systematic review of clinical and epidemiological features of the pandemic influenza A (H1N1) 2009.

ABSTRACT: The aim of this systematic review was to summarise the clinical and epidemiological features of the pandemic influenza A (H1N1) 2009. We did a systematic search of published literature reporting clinical features of laboratory-confirmed pandemic influenza A (H1N1) 2009 from 1 April 2009 to 31 January 2010. Forty-four articles met our inclusion criteria for the review. The calculated weighted mean age of confirmed cases was 18·1 years, with the median ranging from 12 to 44 years. Cough (84·9%), fever (84·7%), headache (66·5%), runny nose (60·1%) and muscle pain (58·1%) were the most common symptoms of confirmed cases. One or more pre-existing chronic medical conditions were found in 18·4% of cases. Almost two-thirds (64%) of cases were aged between 10 and 29 years, 5·1% were aged over 50 years and only 1·1% were aged over 60 years. The confirmed case fatality ratio was 2·9% (95% CI 0·0-6·7%), an extracted average from 12 of 42 studies reporting fatal cases (937 fatal cases among 31,980 confirmed cases), which gives an overall estimated infected case fatality ratio of 0·02%. Early in the pandemic, disease occurred overwhelmingly in children and younger adults, with cough and fever as the most prevalent clinical symptoms of the confirmed cases. A high infection rate in children and young adults, with sparing of the elderly population, has implications for pandemic influenza management and control policies.

SUBMITTER: Khandaker G

PROVIDER: S-EPMC5657010 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Systematic review of clinical and epidemiological features of the pandemic influenza A (H1N1) 2009.

Khandaker Gulam G Dierig Alexa A Rashid Harunor H King Catherine C Heron Leon L Booy Robert R

Influenza and other respiratory viruses 20110315 3

The aim of this systematic review was to summarise the clinical and epidemiological features of the pandemic influenza A (H1N1) 2009. We did a systematic search of published literature reporting clinical features of laboratory-confirmed pandemic influenza A (H1N1) 2009 from 1 April 2009 to 31 January 2010. Forty-four articles met our inclusion criteria for the review. The calculated weighted mean age of confirmed cases was 18·1 years, with the median ranging from 12 to 44 years. Cough (84·9%), f ...[more]

PMID: 21477133

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Project description:BACKGROUND:To date, little is known about the initial spread and response to the 2009 pandemic of novel influenza A ("2009 H1N1") in tropical countries. Here, we analyse the early progression of the epidemic from 26 May 2009 until the establishment of community transmission in the second half of July 2009 in Ho Chi Minh City (HCMC), Vietnam. In addition, we present detailed systematic viral clearance data on 292 isolated and treated patients and the first three cases of selection of resistant virus during treatment in Vietnam. METHODS AND FINDINGS:Data sources included all available health reports from the Ministry of Health and relevant health authorities as well as clinical and laboratory data from the first confirmed cases isolated at the Hospital for Tropical Diseases in HCMC. Extensive reverse transcription (RT)-PCR diagnostics on serial samples, viral culture, neuraminidase-inhibition testing, and sequencing were performed on a subset of 2009 H1N1 confirmed cases. Virological (PCR status, shedding) and epidemiological (incidence, isolation, discharge) data were combined to reconstruct the initial outbreak and the establishment of community transmission. From 27 April to 24 July 2009, approximately 760,000 passengers who entered HCMC on international flights were screened at the airport by a body temperature scan and symptom questionnaire. Approximately 0.15% of incoming passengers were intercepted, 200 of whom tested positive for 2009 H1N1 by RT-PCR. An additional 121 out of 169 nontravelers tested positive after self-reporting or contact tracing. These 321 patients spent 79% of their PCR-positive days in isolation; 60% of PCR-positive days were spent treated and in isolation. Influenza-like illness was noted in 61% of patients and no patients experienced pneumonia or severe outcomes. Viral clearance times were similar among patient groups with differing time intervals from illness onset to treatment, with estimated median clearance times between 2.6 and 2.8 d post-treatment for illness-to-treatment intervals of 1-4 d, and 2.0 d (95% confidence interval 1.5-2.5) when treatment was started on the first day of illness. CONCLUSIONS:The patients described here represent a cross-section of infected individuals that were identified by temperature screening and symptom questionnaires at the airport, as well as mildly symptomatic to moderately ill patients who self-reported to hospitals. Data are observational and, although they are suggestive, it is not possible to be certain whether the containment efforts delayed community transmission in Vietnam. Viral clearance data assessed by RT-PCR showed a rapid therapeutic response to oseltamivir.

Dataset Information

Systematic review of clinical and epidemiological features of the pandemic influenza A (H1N1) 2009.

Publications

Systematic review of clinical and epidemiological features of the pandemic influenza A (H1N1) 2009.

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