(This story originally appeared in on Jul 24, 2017)

NEW DELHI: Swine flu the viral illness that became a pandemic in 2009, has made a comeback this year, claiming nearly 600 lives across the country so far this year with close to 12,500 cases being reported. Maharashtra is the worst affected with 284 deaths followed by Gujarat (75), Kerala (63) and Rajasthan (59), government data shows.In Delhi, official figures state, 241 people have tested positive for swine flu and four have died, as on July 9. Doctors said the number of deaths could be higher."People are visiting hospitals late. This is why there have been more deaths. If patients are put on Tamiflu, the drug approved for treating swine flu, as soon as clinical symptoms appear, many lives can be saved," Dr Jagdish Prasad, the director general of health services, told TOI .Clinicians suspect the H1N1 virus, which causes swine flu, may have mutated. The disease initially spread through pigs but now transmits from human to human.A central rapid response team has been deployed in Maharashtra to investigate the rising trend of influenza there, Prasad said.He added that government has put Oseltamivir, marketed as Tamiflu, in schedule H1 to enable it to be sold by all licensed chemists under prescription. The drug was earlier in schedule X, wherein only certain selected pharmacists were authorised to stock it.The growing number of swine flu cases so early in the season has had doctors worried."This is surprising. Swine flu is commonly seen in winter or post-monsoon season. But we have been seeing significant number of cases of swine flu since June in spite of high temperatures that are not conducive for viral growth or transmission," Dr Arup Basu, senior chest physician at SGRH, said.Dr Suranjit Chatterjee, a senior consultant at Apollo Hospitals , said the National Institute of Virology and National Centre for Disease Control should investigate the reasons behind the sudden spurt in swine flu cases. "As clinicians, we need to look out for characteristic symptoms of swine flu throughout the year so that timely action can save lives," he added.Dr Sandeep Nayar, head of respiratory medicine at BLK hospital, said three patients who tested positive for swine flu have died at the hospital in the last few months. "They were referred from other hospitals in critical state," he said. Dr Atul Gogia, senior consultant, internal medicine at Sir Ganga Ram hospital reported five deaths in his hospital this year.At Max Saket, doctors said five to 10 patients were currently being treated for swine flu. "There is a sudden upsurge in swine flu cases over the past few weeks. Those with severe symptoms require admission," said Dr Rommel Tickoo, senior consultant at the hospital.Swine flu, experts say, is a contagious respiratory disease caused by type A strains of the virus. The virus enters the body through inhalation of contaminated droplets or is transferred from a contaminated surface to the eyes, nose or mouth of a person."Symptoms of swine flu are similar to common viral illnesses. But the intensity is higher. Patients feel lethargic, have high grade fever and sore throat, among other symptoms. Treatment is mostly symptomatic," said a doctor.In some cases, patients suffer from nausea or diarrhoea. Severe cases can progress to pneumonia and organ failure, say doctors."Maintaining hygiene is most important. People should wash hands at regular intervals with disinfectants. If there is prolonged fever, one must see a doctor and not ignore symptoms such as difficulty breathing," doctors say.