If you live in a northern climate, winter increases your risk of the flu, head colds, and respiratory illnesses. These are somewhat expected. But winter also brings some less considered infections that you may get if you are lucky enough to go on a winter vacation in a warm climate. For example: Leptospirosis is endemic to Hawaii especially from October to February and is harmful to animals and humans. Coccidioidomycosis (valley fever) is a fungus found in the southwest U.S. and Mexico. Both of these areas are popular winter vacation spots.
In addition, there is an increase in aseptic meningitis causes by the Lymphocytic choriomeningitis (LCMV) virus which is mostly carried by the common house mouse (who gravitates inside for the winter). There is a strange norovirus (called the 'winter vomiting disease') that was described in 1929 in children and seems to peak between December and February.
While I don't want to be Debby Downer (a character on SNL), it is important to be aware of these rare but significant possible exposures. The take-home message??? Have a flu shot, be alert to high risk areas, remember to wash your hands a lot, and avoid sick animals!!!
Source: Wintertime Infections, Beyond the Usual Suspects. edscape. Jan. 13, 2014.