Influenza A(H1N1)pdm09-Associated Pneumonia Deaths in Thailand
et al. (2013) Influenza A(H1N1)pdm09-Associated Pneumonia Deaths in
Thailand. PLoS ONE 8(2): e54946. doi:10.1371/journal.pone.0054946
Influenza A(H1N1)pdm09-Associated Pneumonia Deaths in Thailand
Charatdao Bunthi 0
Somsak Thamthitiwat 0
Henry C. Baggett 0
Pasakorn Akarasewi 0
Ruchira Ruangchira-urai 0
Susan A. Maloney 0
Kumnuan Ungchusak 0
Yi Guan, The University of Hong Kong, China
0 1 International Emerging Infections Program, Global Disease Detection Regional Center, Thailand Ministry of Public Health- US Centers for Disease Control and Prevention Collaboration, Nonthaburi, Thailand, 2 Bureau of Epidemiology, Thailand Ministry of Public Health , Nonthaburi , Thailand , 3 Department of Pathology, Siriraj Hospital, Mahidol University , Bangkok , Thailand
Background: The first human infections with influenza A(H1N1)pdm09 virus were confirmed in April 2009. We describe the clinical and epidemiological characteristics of influenza A(H1N1)pdm09-associated pneumonia deaths in Thailand from May 2009-January 2010. Methods: We identified influenza A(H1N1)pdm09-associated pneumonia deaths from a national influenza surveillance system and performed detailed reviews of a subset. Results: Of 198 deaths reported, 49% were male and the median age was 37 years; 146 (73%) were 20-60 years. Among 90 deaths with records available for review, 46% had no identified risk factors for severe influenza. Eighty-eight patients (98%) received antiviral treatment, but only 16 (18%) initiated therapy within 48 hours of symptom onset. Conclusions: Most influenza A(H1N1)pdm09 pneumonia fatalities in Thailand occurred in adults aged 20-60 years. Nearly half lacked high-risk conditions. Antiviral treatment recommendations may be especially important early in a pandemic before vaccine is available. Treatment should be considered as soon as influenza is suspected.
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Funding: This work was funded primarily by the Thailand Ministry Of Public Health with additional support from the U.S. Centers for Disease Control and
Prevention (CDC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
The 2009 influenza pandemic virus, influenza A(H1N1)pdm09
was first confirmed in the United States by the Centers for Disease
Control and Prevention (CDC) in April 2009 and rapidly spread
worldwide [1,2,3,4]. Clinical manifestations of influenza
A(H1N1)pdm09 infection ranged from mild symptoms to severe
illness and death. Most patients with severe or fatal disease were
reported to have underlying medical conditions, including chronic
lung disease, diabetes, cardiovascular disease, neurological disease,
and pregnancy [5,6,7,8].
The first two cases of laboratory-confirmed influenza
A(H1N1)pdm09 infection in Thailand were reported on May
10, 2009, in exchange students who returned from Mexico.
Although the epidemiology of influenza A(H1N1)pdm09 deaths
has been well-described in the United States, Mexico, and Europe
[1,9,10], less is known about fatal cases in Thailand or other
countries in Asia [11,12,13].
We present epidemiological and clinical data on influenza
A(H1N1)pdm09-associated deaths among persons hospitalized
with pneumonia in Thailand, collected through retrospective
review of medical records.
Ethical Considerations
The medical records reviews were considered by the MOPH to
be part of the public health response to the 2009 influenza
pandemic in Thailand and therefore did not require review by the
human subjects Ethical Review Committee.
In 2004, Thailands Ministry of Public Health (MOPH)
established the National Avian Influenza Surveillance (NAIS)
system in response to human cases of avian influenza A(H5N1).
Under NAIS, hospitals were required to report all cases of severe
and fatal human influenza infection to the Bureau of
Epidemiology (BOE) [14]. In May 2009, at the start of the influenza
A(H1N1)pdm09 outbreak in Thailand, the MOPH encouraged
reporting of all suspected influenza A(H1N1)pdm09 cases through
the NAIS system along with submission of respiratory specimens
(nasopharyngeal swabs, throat swabs, or endotracheal tube
aspirates) to be tested at Thailands National Institute of Health
(NIH) for influenza viruses by real-time reverse transcription
polymerase chain reaction (rRT-PCR). Reports to NAIS were
submitted by hospital epidemiologists (or clinicians) electronically
through a web-based system or using paper forms and included
information on patient demographics, underlying medical
conditions, clinical characteristics, and outcome.
In addition, MOPH established a parallel surveillance system in
early 2009 to support the investigation of severe and fatal
pneumonia cases. Due to the natural overlap with NAIS, cases
from this severe and fatal pneumonia surveillance system were
reported through NAIS, but additional data and specimens were
requested. Under the severe and fatal p (...truncated)