Mumbai: Five more people have succumbed to swine flu in the state over the past two weeks, taking the number of such deaths to 197 this year, so far, while as many as 2,101 people have tested positive for H1N1.
Health experts say the change in climate, global travelling patterns, the transfer of viruses from one place to another and the possibility of an antigenic shift in viruses are the major causes for the increase in the number of influenza cases this year.
“The active transmission of the virus is not limited to cities anymore. Rural parts of the state, such as Satara, Solapur, Dhule, Jalgaon, Latur and Buldhana have also started reporting positive cases and casualties,” said a health official.
In urban areas, Pune, Nagpur, Nashik, Mumbai and Kolhapur have collectively recorded 146 H1N1 deaths. Besides, the Municipal Corporation of Aurangabad has recorded nine deaths, followed by the civic bodies of Ahmednagar (8), Thane (5), Kalyan (5) and Pimpri Chinchwad (3).
Antigenic shift is explained as a major change in the influenza virus, occurring typically when a human flu virus crosses with a flu virus that usually affects animals (such as birds or pigs). When the viruses mutate, they shift to create a new subtype that is different from any seen in humans before.
Experts said diminshed immunity among masses and the co-circulation of other seasonal viruses along with swine flu, are other contributive factors. The wide fluctuation in day and night temperatures is conducive to the spread of the virus.
“Minute changes in the temperature affect the transmission dynamics of a virus. When the temperature is low, the virus remains suspended in air and this leads to a rise in swine flu cases,” said Abhay Chowdhary, the former director of the Parel-based Haffkine Institute.
Doctors said there are far more mutated virus strains this year, as compared to the previous year, leading to an increased number of cases. “The two main groups of influenza virus that we see are H1N1 and Influenza A.
Influenza B virus is spreading fast and there is definitely a very severe strain that was missing in the previous years,” said Dr Om Srivastava, infectious diseases specialist, Jaslok Hospital.
Private practitioners confirmed a rise in H1N1 cases and seeing three patients daily on average. “We continue to see 4-5 new cases of H1N1 every week. There are more patients this year. Patients in the high-risk group are being put on Tamiflu immediately,” said doctors in Mumbai.