From today's Washington Post:
Climate change is creating droughts and floods where they were not common before, and that is also altering patterns and flows of disease. In warming temperatures, mosquitoes are migrating to new areas, carrying diseases once confined to the tropics.
Chikungunya, a tropical disease from Africa and Asia that causes severe joint pain, showed up in Italy in 2006 and has infected several hundred people there. A tourist who visited Kerala, India, is suspected to have carried the virus home. Then the Asian tiger mosquito, which is working its way north as temperatures rise, carried it from one infected person to the next.