Investigation of H1N1 influenza outbreak in a remote hilly region of North India

Abstract

Background: Influenza A/H1N1/2009 Pandemic strain is one of the reemerging viral diseases. Localized outbreaks of various magnitudes continue to occur globally as well as in India. An outbreak of this disease took place in a remote area of North India. We investigated it to find out the etiology and distribution and recommend appropriate control measures. Materials and Methods: On urgent directions from the State Health Department, a team was constituted to investigate the outbreak. The team mapped the area and undertook house to house search of cases on 17th–19th May 2017. Line listing of cases was prepared. Respiratory samples of 13 symptomatic cases were taken. Eight blood samples were also collected for viral serology and blood cultures. Results: Line listing consisted of 61 cases. Attack rate was 25.2/1000 population. Mean age was 13.9 years with a median of 4 years. All cases had fever, followed by cough (67.2%) and sore throat (44.3%). Case–fatality ratio was 1.6%. Epidemic curve showed a common source continuous epidemic with limited spread. The average incubation period was 5 days. Four samples were positive for Influenza A/H1N1/2009 Pandemic strain and two were positive for Influenza A (nonswine). Conclusion: It was a confirmed outbreak of pH 1N1. A similar outbreak here in April 2010 suggests the endemic presence of this virus, and in future, as the susceptible population again rises to a threshold level, another outbreak may occur in this area. Utmost priority should be accorded for continuous monitoring and surveillance along with intensified IEC activities.