On swine flu surge, medical body ICMR’s advice on testing, end of the wave

Why are more seasonal flu cases being reported?

Seasonal flu is a common infection that usually has two peaks in the country: one, during the winter months of January to March and two, towards the end of monsoon season. “This is the increase that we are seeing right now, but there is no cause for concern as there is no increase in mortality,” said Dr Bahl. H1N1, earlier commonly referred to as swine flu, now behaves as a seasonal influenza virus that circulates regularly.

He said that the infection is currently on the rise and is likely to plateau or go down over the next few weeks as per data from the ICMR surveillance network.

The current rise in H1N1 infections across India is part of the seasonal influenza pattern, with no new strain of the virus identified, Bahl added, urging people not to panic as the vast majority of infections are mild and self-limiting.

According to ICMR surveillance, Influenza A (H1N1) pdm09 is currently the dominant respiratory virus being detected among people presenting with cough and cold symptoms. “H1N1 accounts for around 97-98 per cent of detected Influenza A infections, while H3N2 accounts for about 2-3 per cent. Influenza B, particularly the Victoria lineage, is also circulating but is not predominant,” said Bahl.

The circulating H1N1 virus belongs to the familiar Influenza A (H1N1) pdm09 lineage, which has been present since the 2009 pandemic and has subsequently become an endemic, seasonal influenza virus. He said since influenza viruses characteristically mutate over time, such mutations do not, by themselves, indicate the emergence of a new strain.

Why intensive testing is not needed now

Dr Bahl explained that people needed to get tested during the Covid-19 pandemic because it was a new infection, the scientists were still trying to figure out the pattern, and 5-7% of all cases were becoming severe, while 2% were dying in the beginning. Testing, in such a scenario, allowed the government to plan its response better. This is not needed for seasonal flu, which is an endemic infection. “Now, we don’t even test for Covid-19 because we do not see such severe disease anymore,” said Dr Bahl.

How do we know the flu is on the rise if there is no testing?

That’s because of greater surveillance. The ICMR has a network of 73 viral laboratories in tertiary care hospitals across the country. These laboratories routinely collect and test samples from people with respiratory infection — around 1,500 samples each week. All these samples are not just tested for H1N1 but other common respiratory infections such as Covid-19 and RSV.

Since the number of tests being conducted remains the same, these surveillance sites can inform when there is an increase in a particular infection.

India’s respiratory-virus surveillance has been strengthened substantially since the COVID-19 pandemic, Dr Bahl said. Data is collected through multiple layers, including surveillance under the Integrated Health Information Platform and the National Centre for Disease Control, along with ICMR’s sentinel surveillance network covering 73 laboratories or hospitals across the country. “The surveillance network is currently showing a marked predominance of H1N1 among Influenza A viruses. COVID-19 infections are also being detected, but they have been declining after a slight increase earlier,” he added.

The ICMR chief cautioned against attempting to calculate a nationwide total of H1N1 infections by extrapolating sentinel surveillance figures.The surveillance system is designed to track circulating viruses and trends, while ICMR does not measure total hospital admissions attributable to these infections. A reliable national case count would require testing everyone, which is not being recommended, he explained.

High-risk groups advised to exercise greater caution

The ICMR has urged people at higher risk of complications —including elderly persons, immunocompromised individuals and pregnant women — to take additional precautions. Such individuals should minimise contact with people who are sick, maintain hand hygiene and avoid places where large numbers of sick people may be present. They may also consult their doctors about influenza vaccination, which can be considered for high-risk individuals when medically recommended.

People with flu-like symptoms have been advised to maintain adequate fluid intake, eat properly and get sufficient rest. They should avoid close contact with others, cover their mouth and nose while coughing or sneezing, wash their hands frequently and maintain distance from people who are ill. Medical attention should be sought if symptoms become serious, particularly in the event of difficulty breathing or chest pain.

Who should get the flu vaccine?

While the World Health Organisation (WHO) recommends annual vaccination for people at risk for severe disease — healthcare workers, those over the age of 65 years, people living with comorbid conditions that increase the risk of severe disease, those with compromised immune system, and pregnant women — the vaccine is not recommended for all as part of an immunisation programme in India.

“However, the vaccine is readily available and those who are at a high risk may choose to get it after consulting their doctor. They should prefer to get the vaccine recommended for the northern hemisphere as it is likely to be closer to the strains in circulation and therefore offer better protection,” said Dr Bahl.