Why is the Flu More Prevalent During the Winter? October 6, 2017 By Josh Martinez Leave a Comment Many viruses and diseases are a yearround problem. They can strike populations around the world at any time or season throughout the year. Diseases like hepatitis, meningitis and chickenpox can infect a person at any time during the year. But, it’s the viruses that only spread certain times of the year that we tend to worry about the most. Whether it’s seasonal allergies, the common cold, sinus infections or influenza, some illnesses can cause panic one time of the year. Fall has begun and with the new season comes the busiest time for the flu. But why does the flu strike people during the colder months? The flu virus targets the respiratory system. The symptoms are similar to the common cold, with the viruses often mistaken for each other. Although they are two types of viruses, both versions thrive in the warm, moist environment that humans provide. This allows the bacteria to survive, regardless of the cold weather during the winter. Once an individual has been exposed to the virus, they can expect symptoms to begin within a week of encountering the germs. It is during this period that the person is contagious and can spread the virus to others. We may know how the virus gets into they human body, but that doesn’t answer why it’s more likely to happen during winter. Without one concrete answer, research point to these various reasons for the flu’s seasonal spread: Close Quarters People are often cooped up in the wintertime. Many spend far less time outdoors and don’t get a chance to exercise. Anyone that’s free of the flu may be forced to share close quarters with a person that’s battling the virus. Even being careful, a sick person will get some of their infected bacteria into that shared air. For instance, even if you cover your nose or mouth, tiny droplets are released into the air every time we cough or sneeze. Researchers believe that these germ-filled droplets survive better when it is cold outside. The flu virus also flourishes in dry air with little humidity. Put these two traits together, and you have a perfect atmosphere to prolong the life of the cell. Limited Vitamin D The winter months also mean less exposure to sunshine. Other than giving us a bright demeanor, that sunshine is key for nutrients. The human body makes vitamin D via exposure to sunlight. One of the greatest purposes for vitamin D is to regulate the immune system. With less exposure to sunlight, and the natural source of vitamin D, the immune system tends to suffer. While you can get vitamin D from eating fish, dairy products and egg yolks, the nutrient’s greatest source is sunlight. Unless you brave the cold weather to get some sun, your immune systems will suffer in the winter. Cold and Dry Air As already mentioned, the flu virus has an extended cell life in the dry, cold air. But how cold and dry does it have to be? A study from 2007 tested what combination of humidity and low temperatures worked best for the flu virus. The virus could last for almost a day in low humidity with a temperature of 43 degrees. Unfortunately, no matter where you travel in the world, there is no escaping influenza. Wherever there is a winter season, there will be the flu. Your chances may be better of catching the flu in the winter, but things aren’t hopeless. By showing extra caution throughout the season, you can greatly reduce chances of catching the virus. The CDC recommends washing your hands whenever possible, staying home when sick and trying not to touch your face. It doesn’t stop all droplets, but covering your mouth when sneezing and coughing can also slow the spread. The flu vaccine can also help keep you healthy during the flu season. Unsure where you can get the flu shot? Passport Health can help! Give us a call at or book an appointment online to speak to a health specialist. Did we miss any crucial information about flu’s spread? Let us know in the comments or via Facebook and Twitter. Written for Passport Health by Sabrina Cortes. Sabrina is a freelance writer with a Bachelor’s Degree from Georgian Court University. She currently lives in the Smokey Mountains of western North Carolina.