Contrary to popular belief, flu season isn't just restricted to winter. Different regions of the world experience flu seasons at different times. In temperate countries, such as in North America, flu strikes hardest in the winter. In tropical regions, however, it peaks with heavy monsoon rains.
Many factors contribute to the increased prevalence of the flu in North America during the winter months. Colder temperatures and lower humidity levels are ideal conditions for the virus. Additionally, low temperatures keep people inside, sharing air - and airborne viruses - with anyone nearby.
Unfortunately, influenza is not the only illness that gets worse in the winter. The shift in temperature, humidity and subsequent changes in behaviors (such as staying inside) can exacerbate a variety of ailments, from heart attacks to asthma. At HealthGrove, we looked at nine common maladies that worsen in the winter and provide explanations as to why.
As previously mentioned, factors such as temperature and humidity greatly influence flu seasons around the world. According to the Journal of Virology, influenza epidemics peak between November and March in the Northern Hemisphere and between May and September in the Southern Hemisphere.
In their studies, the scientists found the virus was most readily transmitted at low temperatures (5 degrees celsius) and low humidity (20-30 percent relative humidity) - conditions that match up with typical, northern winters.
Though it can strike year round, norovirus is most infectious during the winter. Also known as the "winter vomiting bug," norovirus typically lasts only a few days and if you stay well hydrated, you should make a full recovery.
Unfortunately, there are many different types of noroviruses. According to the CDC, you can get the bug by eating contaminated food or interacting with contaminated people or surfaces.
Also known as "yersiniosis," yersinia is an infectious disease spread by contaminated food, especially raw or undercooked pork. Common symptoms develop four to seven days after exposure and can last from one to three weeks. Abdominal pain and fever are the predominant symptoms, though rashes and joint pain can occur sometimes as well.
Cold air can exacerbate asthma symptoms, such as shortness of breath and wheezing. Rain and wind also stir up allergens, which can make asthma worse. Additionally, working out in cold temperatures can be especially problematic - the cold air causes bronchoconstriction (narrowing of the airways), thus making it even harder to breathe.
Though no studies have shown a significant association between weather and arthritis pain, many people suffering from the disease claim there is one. Some doctors, despite the lack of scientific evidence, even provide theories as to why arthritic joint pain may worsen in the winter.
Dr. James Fant, professor of medicine at the University of South Carolina, explains that as temperatures lower, muscular tissues can shrink and pull on nerves, thereby causing pain. Additionally, people tend to lead less active lifestyles in the winter, and this causes joints to stiffen.
#6. Heart Attack
Cold snaps can increase blood pressure, which puts more strain on the heart. Your heart also has to work harder to keep your body warm during the winter months. Biological studies have also shown that cold temperatures can contribute to atherosclerotic plaque in blood vessels. Lower temperatures activate brown fat, which converts fat to heat. This is different from the white, and more common, type - what we normally think of when we think of fat. Unfortunately, as a side effect of converting fat to heat, this process also increases the amount of fat stored in blood vessels. This buildup can contribute to heart attacks.
Bronchitis, the swelling and irritation in the air passages of the lungs, often occurs in the winter. It often starts because of another illness, such as the cold or flu. The most common symptom of acute bronchitis is a frequent cough. In healthy individuals, it usually goes away on its own. Though it is not a serious illness, it can last anywhere from a few days to over a month.
Pneumonia, inflammation of the lungs, occurs more in the winter. The flu virus is one of the most common causes of viral pneumonia - and since the flu often occurs in the winter, so does pneumonia. It causes the small air sacs in your lungs (alveoli) to fill with fluid. This, coupled with your body's immune response of sending white blood cells to the area to fight infection, can make it very hard to breathe. Most healthy people recover within one to three weeks. However, it can be life-threatening for at-risk populations, such as children and the elderly.
#9. Whooping Cough
Also known as pertussis, whooping cough is most common in adolescents and adults. It is highly contagious and causes severe, violent, uncontrollable coughing. However, most healthy adults get over it in a few days. This condition is most fatal in young children that have not received the vaccine or those with weak immune systems.