The World Health Organisation has warned that a third of the world would be affected by the end of the H1N1 pandemic.

While experts have not confirmed the strike of the second wave of swine flu, the growing number of swine flu cases in Delhi give a different picture.

Around 78 cases were reported in the Capital on Monday.

"Low temperatures favour the spread of the flu externally. As during winters the blood circulation is low in the human body as blood capillaries close down to conserve heat and that is why most viruses become severe during winters," says Dr Sapatnekar.

Swine Flu cases across India had plateaued between September and October but in the Capital, with the mercury dropping to 7.9 degree Celsius on November 28 - New Delhi's lowest temperature in the season - an alarming 111 cases of the swine flu were confirmed.

Winters have set in across the Northern Hemisphere and Europe is also seeing a rise in cases.

Though authorities say the number of cases in the US, has fallen, the World Health Organisation reported about 850 deaths in just one week from across the Americas and Europe.

Mutations have been reported from France, Norway, China - where disturbingly, the bird flu virus is endemic.

While vaccines are still said to be effective, the WHO has confirmed 75 cases where the virus is resistant to the anti-viral drug oseltamivir.

However, no mutations have been reported from India so far.