Outbreak of pandemic influenza A (H1N1) among children of an orphanage home and further spread among their contacts, Chennai, South India, 2009-10

Background: On 11December 2009, one of the administrative regions of Chennai corporation reported a cluster of influenza like illness (ILI) among students of an orphanage. We investigated the outbreak to identify the cause and propose control measures.

Methods: We defined a suspected case of A (H1N1) influenza as occurrence of fever > 38 0C, respiratory illness with or without cough, sore throat, nasal catarrh and shortness of breath between 1/12/2009-1/1/2010. We defined confirmed case as a suspect with laboratory confirmed influenza A (H1N1). We conducted active surveillance among resident and non-resident students, family contacts and collected information on exposure and symptoms. We described the outbreak by time, place and person. We collected nasopharyngeal specimens to confirm A (H1N1) by PCR. We implemented control measures.

Results: We identified 173 case-patients among 1769 at risk individuals (residents=224; non-residents=1545) (Attack rate: 10%; No deaths). The attack rate was higher among residents than non-residents, 5-14 years (21%) and females (11%). Secondary attack rate was 0.4% (7/1758). The attack rate among the residential children (4.9%, 11/224) was higher than non-residents (0.5%, 7/1545). The illness initially occurred among residents of the home with the first case-patient developing the illness on 10 December 2009 and subsequently spread to non-residents and peaked during 12-14 December 2009. Of the 57 tested, 18 were positive (26%) for A(H1N1). All the confirmed cases attended a cultural event on 6 December and none of the participants had ILI.

Conclusions: We confirmed an outbreak of A (H1N1) influenza among residents of an orphanage, which then spread among non-residents without causing severe illness. We recommended continued surveillance among the residents and non-residents of the orphanage and preventive measures to restrict the spread.

Key words: Pandemic influenza 2009, Chennai, India

For more information, email the presenter at: indiafetp@gmail.com

Author (s): 

Mahalakshmi S, Manickam P, Kuganantham P, MV Murhekar

Presenter (s): 
Dr. Mahalakshmi Srinivasan
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