A Retrospective Surveillance Study on Emergence and Consistency of Influenza like Illness Caused by Influenza Strains over a Period of Three Decades in Solan, (Himachal Pradesh), India

Abstract

In connectivity to the introduction of frequent epidemics of influenza A (H3N2, H1N1), the Influenza Surveillance Projects has monitored the burden of influenza in the outpatients through population-based surveillance. WHO is playing an active role by keeping an eye on status of seasonal as well as epidemic strains of influenza by its surveillance throughout the world. The present study offers the status of ongoing surveillance influenza at National Influenza Surveillance Centre (NISC), Central Research Institute (CRI), Kasauli for the emergence and consistency of influenza strains for current as well as over a period of three decades in Solan, Himachal Pradesh. From 1980 to 2015, various clinical centers of Himachal reported counts of influenza-like illness (fever including cough or sore throat). During these years, the respiratory specimens of 6581 patients showing influenza-like illness were collected. The incidence of visits had been calculated for influenza-like illness using the size of the patient population, and the incidence attributable to influenza was extrapolated from the proportion of patients with positive tests. Up to 2008 the egg inoculation method was used for the isolation and detection of influenza strains but in 2009 a RT-PCR equipped, fabricated BSL-3 laboratory was implanted at CRI for the isolation and detection of influenza strains. The reagents, primers and probes were supplied by NCDC, Delhi. Since 1980, 319 influenza isolates has been identified and isolated at NISC. Among these 282 were isolated by egg propagation method while 37 were processed by RT-PCR. Influenza incidence varied with age groups and by season after the pandemic of 2009 influenza A, H1N1. High levels of influenza virus circulation, especially in young Children, emphasize the need for additional efforts to increase the uptake of influenza vaccines and anti-viral. The continuous surveillance and monitoring of influenza strains is necessary to keep a check on the highly variable influenza strains to avoid the deadly incidents of influenza pandemics. In current scenario RT-PCR method is successful and appropriate method for the influenza surveillance.