Mild form of 2009 H1N1 influenza infection detected by active surveillance: Implications for infection control

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Am J Infect Control. 2010 Apr 22. [Epub ahead of print]
Mild form of 2009 H1N1 influenza infection detected by active surveillance: Implications for infection control.

Jeong I, Lee CH, Kim DK, Chung HS, Park SW.

Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine and Lung Institute, Seoul National University College of Medicine, Seoul, Republic of Korea.
Abstract

BACKGROUND: Screening patients with suspected influenza is a key step for infection control within communities and institutions. By analyzing the clinical characteristics of mild 2009 H1N1 influenza cases detected by active surveillance, we assessed the utility of the commonly used influenza case definition. METHODS: We retrospectively reviewed medical records of 44 patients who were hospitalized and quarantined and who tested positive for the 2009 H1N1 virus using real-time reverse-transcriptase polymerase chain reaction between May 29 and July 28, 2009. RESULTS: Patient median age was 17 years (range, 8-79 years), and 37 patients were male (84%). Common symptoms included cough (34/44; 77.3%), subjective fever (23/44; 52.3%), rhinorrhea or nasal congestion (22/44; 50%), sore throat (19/44; 43.2%), and diarrhea (7/44; 15.9%). All patients were treated with oseltamivir after the onset of initial symptoms (mean, 2.6 days). Common laboratory test results included leucopenia (23/44; 52.3%) and mildly elevated C-reactive protein (26/44; 59.1%). CONCLUSION: There were many mild afebrile cases of the 2009 pandemic H1N1 influenza. Cough, mild leukopenia, and mildly elevated C-reactive protein were relatively common clinical manifestations. Thus, case-based surveillance for the index cluster of 2009 pandemic influenza is not an effective method for infection control in communities or hospital settings. Copyright ? 2010 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Mosby, Inc. All rights reserved.

PMID: 20416971 [PubMed - as supplied by publisher]

http://www.ncbi.nlm.nih.gov/pubmed/20416971

 

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Re: Mild form of 2009 H1N1 influenza infection detected by active surveillance: Implications for infection control

August 2, 2010 ? The commonly used influenza case definition of H1N1 2009, which includes fever, may miss many cases and be ineffective for infection control within communities and institutions, new research suggests.

Ina Jeong, MD, from the Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine and Lung Institute, Seoul National University College of Medicine, Republic of Korea, and colleagues reported the findings in the August issue of the American Journal of Infection Control.

"Fever over 37.8?C (100?F) with respiratory symptoms has been used as a case definition criteria for influenza," Dr. Jeong and colleagues write. "However, little is known about how this tool has been effectively applied to the 2009 H1N1 influenza pandemic situation."

In South Korea, from the beginning of the H1N1 outbreak in May 2009, all patients with confirmed 2009 H1N1 influenza were to be hospitalized and quarantined to a government-designated hospital, although this policy was abandoned in July 2009 because of the large number of patients infected.

The researchers retrospectively reviewed medical records of 44 patients testing positive for H1N1 who were quarantined during that time. Median age of the patients was 17 years (range, 8 - 79 years). Of the patients, 77% had cough, 52% had fever, 50% had rhinorrhea or nasal congestion, 43% had sore throat, and 16% had diarrhea.

Patients were treated with oseltamivir within an average of 3 days of onset of symptoms. Lab tests included decreased white blood cell count in 52% of the patients and increased C-reactive protein in 60%.

"Although findings were generally nonspecific, cough, mild leukopenia, and mildly elevated [C-reactive protein] were relatively common clinical manifestations," Dr. Jeong and colleagues note. In contrast, "case-based surveillance for the index cluster of pandemic influenza is not an effective method for infection control in communities and hospital settings."

According to the researchers, the most sensitive indicator of H1N1 was cough, present in 77% of the patients, which the researchers suggest may reflect the nature of lower respiratory infection by the influenza virus.

http://www.medscape.com/viewarticle/726158