Mint Explainer: How the 'twin burden' of influenza and air pollution is wreaking havoc on public health

Taking cognisance of the situation, Union health minister J.P. Nadda has directed a comprehensive review of preparedness in all district hospitals and medical colleges within the next fortnight.

Meanwhile, doctors in northern Indian states, particularly in the national capital region, describe the situation as a public health “havoc", noting that severe air pollution is exacerbating the impact of the viral surge.

Mint takes a close look at why this is a matter of concern for the government and the public.

What do the latest trends show?

The ICMR data shows a sharp upward trend beginning in late September, when the monsoon begins to withdraw, with positive cases peaking significantly by November.

The positivity rate in samples collected from hospitals (severe acute respiratory infections) and community settings (acute respiratory infections) spiked to 12–13% by late November, with weekly positive cases nearing 200 out of approximately 1,600 samples tested per week—a significant jump from the low single-digit positivity rates seen during the monsoon months.

While full data for December is still being compiled, the case trajectory entering the month remains steeply upward, showing no immediate signs of plateauing. This indicates that the virus is spreading rapidly through the community as winter sets in. Although the surge is nationwide, Kerala, Delhi, Maharashtra, Tamil Nadu, Gujarat, and Puducherry are reporting the highest number of cases, necessitating focused surveillance.

How has air pollution worsened the situation?

The convergence of hazardous pollution levels and the viral spike creates a “twin burden" for public health. According to experts, particulate matter 2.5 (ultrafine particles less than 2.5 micrometres in diameter, small enough to penetrate deep into the lungs and bloodstream) damages the respiratory tract's protective mucous lining (epithelium). This inflammation makes the lungs more “sticky", increasing susceptibility to viral attachment. When a patient contracts the flu in highly polluted air, symptoms such as breathlessness, coughing, and wheezing become more severe, and recovery times are significantly prolonged.

Dr Sanchayan Roy, senior consultant of internal medicine at Apollo Spectra Hospital, Delhi, noted that air pollution is exacerbating the severity of symptoms, particularly in infants, adults, young women, pregnant women, and individuals with chronic conditions.

He added that while outpatient departments are operating at full capacity, the focus remains on early diagnosis and timely antiviral therapy for high-risk patients.

Which influenza strains are currently circulating, and is a vaccine available?

The circulating strains are the usual seasonal variants, but the primary driver of the current surge is H3N2, according to the nodal agency in the country for disease surveillance, the National Centre for Disease Control (NCDC). This is significant because H3N2 is historically associated with more severe disease and higher hospitalization rates. Influenza B (Victoria lineage) and a smaller proportion of H1N1 cases are also being reported.

Experts strongly recommend the annual quadrivalent flu vaccination, which covers four strains, including the currently circulating H3N2 and H1N1. While not part of the government's universal immunization programme for adults, the vaccine is widely available in the private market. Vulnerable groups—including the elderly, children under five, pregnant women, and those with comorbidities like asthma or diabetes—are advised to get vaccinated 2-3 weeks before the peak winter season to ensure immunity.

Does the government view this as an unusual outbreak?

Although the health ministry, in a 2 December press statement following a high-level review, maintained that surveillance shows “no unusual surge" and activity remains low relative to historical trends, the ICMR data prompted it to call for quick action.

To manage the upcoming winter peak (January-March), Nadda has mandated a series of immediate actions. A review of preparedness in all district hospitals and medical colleges must be completed within the next fortnight to ensure readiness. Furthermore, he has directed that regular mock drills be conducted at health facilities to ensure they can handle increased patient loads. Additionally, the NCDC will convene a two-day high-level national strategy meeting ('chintan shivir') later this month with state governments to review influenza preparedness and plan the way forward.