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Influenza surveillance in Pune, India, 1978-90
1National Institute of Virology, Pune, India.
Abstract:
Continuous surveillance of influenza was carried out in Pune between 1978 and 1990. Most of the cases were identified during investigation of 16 outbreaks of influenza in Pune over this period. The majority of cases were children. Ten of the outbreaks occurred during rainy seasons. A total of 290 isolates consisting of several antigenic variants of influenza type A (H3N2), type A (H1N1), and type B viruses were isolated from throat/nasal swabs that were processed in chick embryos and MDCK cell culture and identified using the haemagglutination inhibition test. These variants circulated every year or in alternate years. Nearly two-thirds of the influenza virus isolates (181 out of 290) were from children aged < 10 years. Seasonal analysis indicated that the highest number of isolates (174) were collected during the rainy months of July, August and September, with the maximum number (93) in July.
Insights
Influenza surveillance in Pune from 1978-1990 identified numerous outbreaks, primarily affecting children. Antigenic variants of influenza A (H1N1, H3N2) and B circulated annually, with most cases occurring during the monsoon season.
Area of Science:
- Virology
- Epidemiology
- Public Health
Background:
- Continuous influenza surveillance is crucial for understanding viral circulation and disease burden.
- Pune experienced numerous influenza outbreaks between 1978 and 1990, necessitating detailed epidemiological study.
Purpose of the Study:
- To document the epidemiological and virological characteristics of influenza in Pune over a 12-year period.
- To identify circulating influenza virus strains and their seasonal patterns.
Main Methods:
- Conducted continuous surveillance for influenza in Pune from 1978 to 1990.
- Isolated and identified influenza virus strains (A/H1N1, A/H3N2, B) using chick embryo and MDCK cell culture, confirmed by hemagglutination inhibition tests.
- Analyzed data from 16 identified influenza outbreaks.
Main Results:
- A total of 290 influenza virus isolates were obtained, including various antigenic variants of types A and B.
- Children under 10 years old accounted for the majority of cases (181/290).
- Peak isolation occurred during the rainy season (July-September), with the highest number in July.
Conclusions:
- Influenza, particularly in children, poses a significant public health concern in Pune, with distinct seasonal patterns.
- Annual circulation of diverse influenza virus variants requires ongoing monitoring and potential vaccine updates.