In those regions, there may be outbreaks during rainy, humid months or relatively consistent levels of flu cases all year round. This may seem counterintuitive. Indeed, although influenza data do support such a link, scientists do not fully understand how viruses are able to exert their maximum damage at both low and high temperature and humidity extremes.
There are several theories, however, ranging from the cold affecting how viruses behave and how well our immune system copes with infections to spending more time in crowded places and getting less exposure to sunlight. Common cold and flu viruses try to gain entry into our bodies through our noses. However, our nasal lining has sophisticated defense mechanisms against these microbial intruders.
Our noses constantly secret mucus. Viruses become trapped in the sticky snot, which is perpetually moved by tiny hairs called cilia that line our nasal passages.
We swallow the whole lot, and our stomach acids neutralize the microbes. However, cold air cools the nasal passage and slows down mucus clearance.
Once a virus has penetrated this defense mechanism, the immune system takes control of fighting off the intruder. Phagocytes, which are specialized immune cells, engulf and digest viruses. However, researchers have also linked cold air to a decrease in this activity. Rhinoviruses actually prefer colder temperatures, making it difficult not to succumb to the common cold once the thermometer plummets.
In one laboratory study , these viruses were more likely to commit cell suicide, or apoptosis, or to encounter enzymes that made short work of them when grown at body temperature.
During winter, levels of UV radiation are much lower than in summer. This has a direct effect on how much vitamin D our bodies can make. There is evidence to suggest that vitamin D is involved in making an antimicrobial molecule that limits how well the influenza virus can replicate in laboratory studies.
Consequently, some people believe that taking vitamin D supplements during the winter months can help keep flu at bay. Indeed, a clinical trial showed that school children who took vitamin D3 daily had a lower risk of contracting influenza A.
A systematic review concluded that vitamin D provided protection against acute respiratory infection. However, there have been no large-scale clinical trials to date, and discrepancies between individual studies make it difficult for scientists to draw firm conclusions. Another factor that may contribute to cold and flu infections in the fall and winter months is that we spend more time indoors as the weather becomes less hospitable.
This might lead to two effects: crowded spaces helping spread viruses-laden droplets from person to person, and central heating causing a drop in air humidity, which — as we have already seen — is linked to influenza outbreaks. However, many of us live our lives in crowded spaces all year round, and in isolation, this theory cannot explain flu rates.
Scientists continue to study seasonal patterns of respiratory infections to tease out how different factors may influence their spread. In fact, the CDC estimate that adults have two to three colds each year. You may have been told that you can catch a cold by getting caught in the rain and staying in wet clothes.
Jaime Friedman, a pediatrician in San Diego, said myths relating to wet weather and catching colds probably evolved due to a poor understanding of viruses. According to the Centers for Disease Control and Prevention CDC , every year there are millions of cases of the common cold with the average adult getting 2 to 3 colds every year.
Children typically get even more. The majority of people get colds in winter or spring, but it is possible to catch a cold any time during the year. Seasonal influenza circulates year round in the United States, but the flu is most common in fall and winter. Experts say colder weather can allow the flu virus to circulate more easily, but other factors are also to blame for the increase in influenza cases in the winter and fall.
But in the tropics, flu is often associated with the rainy seasons and may occur year-round or show both winter months and summer months peaks. And many of our pandemics, including the pandemic, seem to appear in the late spring and summer, after the traditional flu season has ended.
Lack of regular exposure to sunlight during the colder months may also impact the immune system, but experts say this is an area that needs further study. Jeffrey Klausner, a professor of medicine in the division of infectious diseases at the University of California Los Angeles, told Healthline. The CDC advises the best way to avoid a cold is to regularly wash hands with soapy water for at least 20 seconds, as well as avoid touching the face, eyes, nose, or mouth with unwashed hands.
You should also try to avoid close contact with those who are coughing and sneezing, as well as regularly disinfect frequently touched surfaces in the home like doorknobs. You probably started with a dry cough that soon became mucus-producing. You may also have aches and pains, chills, headache, runny nose, sore throat, shortness of breath, watery eyes and wheezing. Not much. It will clear up on its own — unless it progresses to pneumonia, which can be treated with antibiotics.
Meanwhile, a humidifier, cough medicine and pain relievers can ease your symptoms. About two weeks for most symptoms, though the cough can linger for a couple of months. Bronchitis is not contagious once the initial viral phase subsides after a few days, so return to work when you feel strong enough. About 5 percent of adults and 6 percent of children are diagnosed with acute bronchitis in the U. Learn more about acute bronchitis. Inflamed bronchi the big tubes that bring air to the lungs , resulting in overproduction of mucus.
Bronchitis is considered chronic if you have a mucus-producing cough at least three months per year, two years in a row. Probably from smoking, but irritants like air pollution may also be to blame. How I feel: You have a persistent cough, plus chest discomfort and difficulty breathing. The goal of treatment is to reduce symptoms so you can breathe more easily. If you smoke, quitting is recommended. Oral or inhaled medications can open your airways. In severe cases, you might consider lung reduction surgery or a lung transplant.
Chronic bronchitis is not contagious, so work if you are able. About 9 million Americans each year are diagnosed with chronic bronchitis. See a doctor if: You have a cough that lasts more than three weeks, produces bloody or discolored mucus, or is paired with a fever. Err on the side of caution and see a doctor even if you only suspect you have bronchitis — early treatment decreases the risk of lung damage.
Learn more about chronic bronchitis. Your lungs are infected, causing air sacs to fill with pus and other liquids. Viruses are responsible for about one-third of cases. The rest are caused by bacteria or fungi that are inhaled, particularly by people weakened by surgery, illness, age or smoking.
If you have viral pneumonia, rest, eat well and drink plenty of fluids. Bacterial pneumonia can be treated with antibiotics. In both cases, medications can ease your fever and cough. Most people respond well to treatment and recover in one to three weeks, but pneumonia can be very serious and even deadly. If you have bacterial pneumonia, the risk of infecting others drops sharply two days after taking antibiotics. Viral pneumonia is less contagious, but avoid others if you have a fever.
About 3 million people in the U.
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