Chennai: Fevers in city hospitals, largely attributed to influenza A and B until two weeks ago, are now increasingly linked to Covid-19. This has prompted surgeons to cancel critical procedures like transplants, bypass surgeries, and heart valve replacements, doctors said.The public health department, which says there are 40 active cases, is yet to confirm whether people with the viral infection have strains similar to Omicron JN.1 descendants—LF.7 and NB.1.8—observed in Singapore and Hong Kong, where there is a rise in cases and hospitalisations.While healthy people with mild disease, treated as outpatients, are not tested, people with co-morbid conditions or those with severe disease requiring admission undergo tests. In most hospitals, including govt-run facilities, the panel of tests includes influenza, Covid-19, and respiratory syncytial virus. “We test for these because treatment for these diseases varies,” said Gleneagles Healthcity infectious diseases expert Dr Subramaniam Swaminathan.Since August 2024, there was a steady flow of patients with fever in the city due to various viruses. “We did not see a dip even when day temperatures were hovering near 40 degrees C. Nearly 60% of cases we tested were influenza A and B two weeks ago. Now, it is Covid,” he said.Most people report symptoms such as fever, nasal congestion, respiratory distress, and a persistent cough, but there is no spike in admissions to intensive care units or deaths reported so far, health officials confirmed. “There is no need for panic,” said Director of Public Health Dr T S Selvavinagayam. “Like influenza-like illness, Covid never completely went away. We have been seeing sporadic cases of the viral infection with seasonal peaks,” he said.On Tuesday, the directorate asked people to wear masks and maintain social distancing when they are in closed crowded spaces. “It is important for the elderly, pregnant women, and people with co-morbid conditions or immunity issues to take precautions,” he said. Educational institutions, workplaces, and public places must provide facilities for people to wash their hands with soap or cleanse them with sanitisers, he added.Doctors also advise people to take the flu vaccination. The flu vaccine prevents flu in up to 70% of cases. It also reduces the chances of severe disease, hospitalisation, and death, particularly among children, pregnant women, the elderly, and people with comorbid conditions such as diabetes and hypertension, said Apollo Hospital’s infectious diseases expert, Dr V Ramasubramanian. “We don’t yet have the Covid vaccination to prevent the present variant of Covid circulating in Singapore.We recommend people at risk to take the existing booster dose if they haven’t taken the vaccine for six months,” he said. The immune response to the flu weakens after six months. The annual vaccination boosts immunity. Additionally, viruses are constantly changing, he added.