Even as dengue and leptospirosis cases have been in check in Mumbai due to delayed monsoon, cases of H1N1 infection, commonly referred as swine flu, have surged to 36 within a fortnight in July this year, against zero cases reported during the month last year.
So far, a total of 1,772 H1N1 flu cases and 191 deaths have been recorded across Maharashtra this year, officials said.
According to data from the civic health department, there were a staggering 3,029 H1N1 flu cases in Mumbai in 2015, which dropped to just three in 2016 and again rose to 995 in 2017. In 2018, 25 cases were recorded with the first case coming up in September, while this year already 309 cases have been recorded in the city.
Last week, Danishta Khan, 26, died due to a suspected co-infection of H1N1 and leptospirosis. A death review committee will now review the case.
State health officials have attributed the haphazard rise and fall in the H1N1 cases over the past few years to variation in the weather pattern — winter was prolonged this year as compared to the previous years. “Usually between January to June there are fewer cases of H1N1 flu, but this year the count is higher. The cyclic trend does not seem to continue. It may be possible due to a prolonged winter this year,” Dr Mahendra Jagtap, attached with state epidemiology cell, said.
Infectious disease expert Dr Om Srivastava said there are also chances of other viral strains going undiagnosed. “We are not actively testing for H3N2 or H7N9 strains, which are found in neighbouring countries. We need more evidence to suggest there is cyclic change, if at all, in H1N1 flu,” he said.
According to the World Health Organisation, H7N9 infections result from direct or indirect contact with infected poultry and are known in rare cases to infect humans, as opposed to H1N1 that commonly infect humans.
Dr Pradeep Awate, state epidemiologist, said H3N2, H7N9 and few other strains are randomly tested for by the National Institute of Virology in Pune, but the state government maintains no data on them.
“Usually, when there is H1N1 flu outbreak, the affected population gains immunity against that viral strain for 8-12 months. That is why we see a decline in subsequent years. But this is the first time we have recorded a high number of H1N1 flu cases in Maharashtra in 2017, 2018 and 2019.”
He added that Indian Council of Medical Research has been conducting research to study the viral strain better. H1N1, a respiratory infection, that started in pigs, causes fever, sore throat, body ache and chills, and causes death in severe complications.
At least 1.5 lakh people across state have been vaccinated against swine flu so far. Most H1N1 flu cases have been reported from Nashik, Nagpur, Ahmednagar and Pune.
The cold wave in last December and this January has played a conducive role for the H1N1 virus to grow, Awate said. He added that with several cases of H1N1 flu in Rajasthan, Madhya Pradesh and Uttar Pradesh and frequent migration from these states, the cases were also getting transferred to Maharashtra.
Meanwhile, leptospirosis cases have also recorded a gradual increase from five in June to 21 within a fortnight in July. According to civic health department, hepatitis infection, that recorded an outbreak in Kurla, has seen a slight decline.
Since June, 204 hepatitis A and E cases have been recorded in Kurla, where water pipeline was contaminated due to civic work. Health minister Eknath Shinde on Monday directed municipal officers to take preventive measures for swine flu, leptospirosis and dengue.