By AlexSosnowskiAccuWeather.comWhile there is no question that common influenza shows a bias during thewinter months, meteorologists have uncovered other possibleroles the weather may play in the H1N1 pandemic, formerly known as the swineflu. These roles range from humidity levels to ultraviolet meteorologists are anticipating an El Niño to developthis summer. The pattern could then last through the coming winter. ElNiño produces warmer-than-normal Pacific Ocean water temperatures off ofCentral and South America and alters the weather pattern in the United Statesand abroad. During a typical El Niño winter, the southern part of theUnited States experiences cooler- and wetter-than-average conditions, while thenorthern part of the nation experiences somewhat milder conditions with lesssnow, compared to average.

Common influenza outbreaks have flourished during the winter months when theair is generally cold and dry. There has been some evidence suggesting thatinfluenza can survive outside the body longer under cold, dry conditions. Arecent study done by Oregon State University indicated that low humidity of airalone could be a determining factor. The study suggested that year-round lowhumidity, such as that of the western U.S. could harbor influenza throughoutthe year.

Indoor humidity levels can drop very low, even if you keep your house coolin the winter. This occurs when air at 20 degrees with a humidity of 50 percentis then warmed to 70 degrees. The humidity level can drop to 10 to 20 percent.

Your house can still be very dry even during a rain or snowstorm in January.

You may want to consider a humidifier as part of your winter householdconditioning system for the upcoming winter. Running a hot shower periodicallymay help as well as keeping a pot of water on top of your wood or coal-burningstove.

Regardless of whether the winter is mild or harsh, winter months typicallyhave more people indoors in colder climates, such as the northern Untied Statesand Canada, northern and central Europe and northern Asia. Meanwhile, in theSouthern U.S. this winter, anticipated rainy conditions may keep moreSoutherners indoors for longer periods of time than average.

College students wear masks at Mexico City'sUniversity of London, Thursday, May 7, 2009(AP Photo/Brennan Linsley)If you are confined indoors for long periods of time with someone who hasthe flu, you are more likely to contract the illness. It is not known whetherthe virus survives in the air by itself, or via transport of moisturedroplets.According to Jonathan Adams, M.D. and Associate Professor of Family andCommunity Medicine at the Pennsylvania State College of Medicine, it appearsthat the more dangerous viruses and pandemics of the past several decades havenot followed the traditional winter season spike. These "mega" viruses havealso been present during the warm, humid season and in tropical climates.

Recall that the most recent H1N1 virus is believed to have originated inMexico. According to Dr. Adams, the H1N1 virus is a combination of swineviruses in North America and Europe, avian viruses and common human viruses.

Adams added, "This strain is something that has not been seen before."Over the next couple of months, it will be interesting to see if the H1N1virus follows that of more common influenza and diminishes in the northernhemisphere and resurges in the more distant winter. Confirmed cases havealready been reported in the southern hemisphere, which will soon be headinginto winter. If the number of confirmed cases of H1N1 swell in the southernhemisphere during the next couple of months, there is the potential for a roughwinter in the north to follow.

The "Spanish flu" pandemic of 1918-1920, a variant of H1N1, first emergedduring the early spring in the northern hemisphere. Then during the northernhemisphere's summer, the virus spread over the southern hemisphere or winterfor down under. During the fall of 1918, the virus exploded in the northernhemisphere as numerous parades and large parties celebrated the ArmisticeTreaty of World War I.

Interestingly, the swine flu outbreak of 1976 was confined to the militarystationed Fort Dix, N.J., during the summer.

There may be another important connection to influenza outbreaks. Dr. Adamspointed out that some studies have indicated a vitamin D deficiency can putpeople at risk of upper respiratory infections, such as influenza. As far as aweather connection with this, vitamin D levels in humans are at their lowestlevels during the late winter and early spring. In order for the body to makevitamin D, the skin must absorb a certain amount of ultraviolet rays from thesun. If the sun's angle is too low in the atmosphere, as it typically is duringthe winter months, the body cannot make a sufficient amount of vitamin D.

In this scenario, it is possible that a modern, well-balanced diet,sufficient in vitamin D could be a deterrent for influenza.

The current H1N1 pandemic is no doubt being spread by the rapid globaltravel of our time. As the summer season comes into bloom in the northernhemisphere, it is possible confirmed cases of H1N1 may soon level off ordiminish.

There are other factors to consider, such as the strain (nature) of thevirus itself, individual immunity and the potential for the the virus tomutate.

Now is a good time to practice common sense hygiene: wash your hands aftertouching keyboards, sharing phones, hand-to-hand contact, etc. If you areexperiencing flu-like symptoms, call your doctor, avoid public places,mass-transit and travel. Cover your mouth when sneezing, discard used tissuesimmediately and, again, wash your hands.

Story by Expert Senior Meteorologist Alex Sosnowski