The virus need...

I was reading this article from Syfy News.

New Delhi, Nov 22 (IANS) Swine flu cases have come down significantly with only about 22 cases and one death being reported across the country during the last week.

According to the health ministry, 22 cases of H1N1 have been reported between Nov 16 to 21, across three states. The lone death was reported from Orissa, which did not report any fresh case.

Tamil Nadu had the highest number with 11 cases while Karnataka had four cases and Rajasthan had six.

According to experts, the swine flu cases will come down further as winter approaches as the virus needs moisture and heat to thrive.

I am wondering about that affirmation the virus needs moisture and heat to thrive.