Influenza A virus driving flu cases in Bengaluru

Infectious disease experts at city hospitals say that Influenza A virus seems to be predominantly responsible for the increasing cases of upper respiratory tract infections now.

These infections are seasonal, with symptoms of cold, cough, fever and body ache. It resolves naturally in most cases, but fever and post-viral cough last longer than usual.

Dr John Paul M, infectious diseases consultant, says they do molecular diagnostics on samples of patients with severe illness, and most results are of Influenza A.

Severe illness is seen only in vulnerable groups like infants, elderly, pregnant women and those on immunosuppressants. For others, only supportive treatment is given.

"About 20 to 30% of patients return after one to two weeks as they have a distressing cough that doesn't resolve. Of them, nearly a third then have to take a short course of bronchodilators to control cough. Many of them are using inhalers for the first time in life," says Dr Paul. "Also, patients who had childhood or adolescent bronchitis and had fully recovered from it, seem to have a resurgence of bronchitis after the flu."

Infectious diseases consultant Dr Chintan Kaswala says that the H3N2 strain of Influenza A virus is identified in eight out 10 patients.

"This is a common strain. But while fever usually lasts two to three days, this time it's lasting up to five days. And in some, cough lasts longer than two weeks."

Infectious diseases consultant Dr Pruthu N Dhekane says that more cases of Influenza B and RSV are also seen this time, which were fewer pre-Covid. "But the treatment protocol for all of these viruses are the same. Most labs can test only for some prominent strains. Unless there is a severe disease or announcement about a variant of concern, in-depth testing may not be done."

Experts believe that the illness lasts longer this time because people had not been exposed to these viruses in the last few years.

"When Covid was predominant, we were not exposed to the usual community-circulating viruses for a long time. So our natural immunity to them would be lower. Also, viruses undergo minor mutations every season, which makes us more susceptible to them," says Dr Paul. "There doesn't seem to be any major mutation this time."

Dr Ashok M L, Professor at BMCRI, says that the number of flu patients has increased by 30 to 40% compared to last month.

Doctors recommend masking up in crowded and closed spaces and following hand hygiene to reduce spread. Taking annual flu shots would also prevent the disease, they say.