A day after Femida Panwala (33) became the first victim of the H1N1 virus in Mumbai, the civic administration said she had contracted the virus “through the air” and that the epidemic had moved to its next phase of virus spread.

The Brihanmumbai Municipal Corporation (BMC) said Panwala was an ‘indigenous’ case and investigations into her medical history had led them to conclude that she had contracted the disease from the environment and not due to her proximity to a patient or contact. “The virus is still the mildest strain,” said Dr Sanjay Oak, Director of Medical Education and Research, BMC.

Experts however explained that the viruses in milder strains could be more potent as they spread to more people than a deadlier strain. The deadlier strain ends with the death of the patient and does not spread further as against a milder strain which spreads within the community.

“At present, the swine flu virus is in the air. So, those of us who have a weak immune system are more likely to contract the disease,” Municipal Commissioner Jairaj Phatak said.

“In the two months that the virus has been in India, there have been an unusual number of cases in different parts of the country, in small numbers. This is the phase one of the epidemic in the country. In phase two, there is a dramatic rise in the number of cases which means that in one day diagnosis there has been a tremendous increase. This is the building up of the epidemiology curve which will rise till it reaches the phase of plateau. In the phase four, it starts decreasing,” said Professor V I Mathan, from the National Institute of Epidemiology, Chennai.