Is flu going around in India?

India's influenza pattern is bimodal, unlike the single winter peak seen across most of Europe. One peak runs through the monsoon months of July–October, and a second builds during the cooler January–March window. The relative strength of the two peaks varies by year and by region, with southern states often showing stronger monsoon activity and northern states a clearer winter rise.

Influenza surveillance in India is carried out by a network of sentinel sites coordinated through the Indian Council of Medical Research (ICMR) and the National Centre for Disease Control (NCDC), with virological support from designated reference laboratories. Aggregated weekly data from these sentinel sites is transmitted to WHO FluNet via the South-East Asia regional reporting framework.

India's sentinel laboratory network submits weekly positivity and subtype-distribution data to WHO's South-East Asia Regional Office, which feeds WHO FluNet. FluNet then publishes India's curves alongside those of neighbouring South-East Asian countries. This makes India's bimodal pattern clearly visible against the single-peak patterns typical of higher-latitude countries.

India's monsoon peak, roughly July through October, is driven by high humidity, crowded indoor conditions during heavy rains, and increased respiratory-virus transmission in south-west and central regions. The winter peak reflects cooler, drier northern winters with patterns closer to temperate seasonality. Together they produce a year-round baseline of flu circulation rather than a single sharp winter window.

Qualitative classification (low, moderate, high) is applied at the sentinel level, anchored to historical reference ranges for each participating site. WHO FluNet publishes the aggregated indicators. Given the bimodal pattern and significant regional variation, these qualitative tiers capture relative pressure better than absolute case counts ever could.