Fever is almost at every home in Calcutta as the seasonal flu has struck in the middle of the Covid season. Hospital outpatient departments and clinics are swamped with people running high temperatures and having chest congestions.

Doctors said the symptoms are often similar to Covid but the test reports are mostly negative.

Some of the private hospitals said they have detected types of influenza virus in many swab samples collected from people suffering from fever. Doctors said although the fever is going away in three to five days, some of the elderly people with comorbidities are getting admitted to hospital.

The number of tests, which had dipped from the first week of July at hospitals and diagnostic centres, have increased again because of the outbreak of the flu, said health department officials.

On Monday, 45, 287 samples were tested and the positivity rate was 1.95 per cent, according to the state health department. On July 5, 40,388 samples were tested with a 2.19 per cent rate of positivity in Bengal.

Doctors said Covid cases could have dropped as many people are vaccinated, still they are not taking chances and asking anyone with fever lasting for two to three days, to get themselves tested.

At the fever clinic of Peerless Hospital, in May during the peak of the Covid pandemic, 275 people would turn up on an average with running temperature. “Results of about 60 percent of those samples tested would be positive. As the number of cases dipped, we would have around 35 people everyday at the fever clinic out of whom barely five percent would test positive for Covid,” said Sudipta Mitra, chief executive of Peerless Hospital.

However, in the last one week, the number of footfall at the hospital's fever clinic has gone upto around 70 everyday, said Mitra. “But less than two per cent are testing positive for Covid. We have detected H3N3, a type of influenza virus in some of the samples tested for flu,” he said.

At RN Tagore International Institute of Cardiac Sciences, during the peak of the pandemic there would be more than 200 people with fever and 60 percent were testing positive. Now, around 15 people are coming everyday at the fever clinic of the hospital but around three percent are detected with Covid, said R. Venkatesh, director of Narayana Health which runs the Mukundapur hospital.

Chandramouli Bhattacharya, tropical medicine and infectious diseases specialist at Peerless Hospital, said the flu is causing fever that usually lasts between three and five days. "It's starting with running nose and then there is high grade fever along with cough and after that most people are getting cured. The clinical presentations are similar to that of Covid but tests are generally coming negative.”

However, two elderly patients with co-morbidites, were admitted under him at the hospital on Monday. Both patients had fever and have tested negative for Covid. "This category of people are still at risk from flu even if they don't have Covid.

At Belle Vue Clinic too, there has been a steady decline in the Covid cases and now it is less than two percent of the samples tested. “There has been an increase in acute respiratory illness since last week of June. These cases were tested to be Influenza A,” said Anuradha Agarwal, head, clinical microbiology and hospital infection control at Belle Vue. She said the quadrivalent flu vaccine can protect people from this.

“The vaccine is safe and should be taken by all with co-morbidities and those above 65,” said Agarwal.

Doctors said although most of the symptoms of influenza virus were similar to Covid, some like diarrhoea and lack of sense of smell are not there. “But still it is important to get everyone tested because the pandemic is not completely over,” said physician Amitabha Saha.

"Now, we have three categories of fever patients, those who have taken two doses of Covid vaccine, others with a single dose and a third section without being vaccinated," said Saha.

"The second wave showed that young people also can get severe Covid infection. A large section of the young people are still not vaccinated and so we cannot take chances," he said. The young people who have to go out for work can also spread Covid again even if they are asymptomatic.

"So, we are asking everyone with fever to get tested," said Saha.