Nobody wants to catch the flu, but is it something to worry about? The severity of a person’s illness, when infected with influenza, depends on various factors, including the person’s age and prior health status. It also depends on which flu strain caused the infection. Numerous versions of the flu virus will circulate in all parts of the world throughout the year, and they also mutate and change from year to year. Each type of infection falls broadly into three categories: Influenza A, B, and C.
Influenza A viruses are the first to peak during “flu season” each year, typically beginning in late fall, and reaching maximum levels of infection in early winter. There are many subtypes of Influenza A, each one identified by the types of hemagglutinin (“H”) and neuraminidase (“N”) proteins on its surface. Humans commonly get one of two strains of Influenza A: H1N1 and H3N2. Every year, these two strains mutate and change. For this reason, people who are immune to one year’s H1N1 or H3N2 viruses are still vulnerable to infection from these strains the following year. The mutations and changes also explain why some years produce strains of flu that are more virulent and deadly than other years.
Infection with an Influenza A virus typically causes high fevers, headaches, fatigue and body pain. While this is true of all Influenza infections, the symptoms associated with Influenza A tend to be particularly severe. A person sick with an Influenza A virus will have these symptoms for 4-5 days, or even a week or more.
Every year, Influenza A is responsible for thousands of hospitalizations and deaths worldwide. True flu pandemics occur only rarely, but when they do, they are always the result of Influenza A viruses. For example, the “Spanish flu” that killed 50 million people worldwide in 1918 was a variety of H1N1 virus, as was the “swine flu” that caused a pandemic in 2009.
Influenza A strains are unique among the three types of flu because they can originate in animals. Sometimes, popular media refer to these strains by the name of the species from which they were transmitted to humans, for example, “bird flu.” The carrier animals do not become sick or symptomatic from the virus.
Every year, researchers try to predict which strains of Influenza A will become the most widespread that season. On this basis, they select two strains for inclusion in the annual flu vaccine.
Influenza B viruses produce a similar illness to Influenza A, although symptoms tend not to be as severe. Unlike Influenza A, however, the B-strain of influenza remains active year-round. It is also more likely than Influenza A, to cause symptoms of nausea and vomiting. Also unlike Influenza A, new strains of Influenza B originate only in human populations.
Although less severe than Influenza A, B-strains of Influenza can still cause hospitalization and death. For this reason, one or two strains of Influenza B are among the annual flu vaccines.
This third category of influenza tends to produce the mildest symptoms. Although found worldwide, it does not mutate as rapidly as the other strains, and therefore does not cause pandemics or even seasonal epidemics. That is why seasonal flu vaccines do not include this strain. Its slower rate of change also allows most people to build up natural antibodies to the virus, usually through exposure to the disease in early childhood.
The number and variety of flu strains circulating and evolving year after year makes it difficult to predict just how uncomfortable the illness will be. It also makes it impossible to guarantee that flu vaccines will prevent a person from becoming infected with the disease. In addition to getting the vaccine and committing to proper handwashing routines, it helps to be aware of which strains of flu are circulating in your area at any given time so that you can assess your risk of becoming infected.
What should I do if I think I have the flu?
If you develop flu-like symptoms concerning to you, you should call your doctor or health care provider. If you are unable to get to your regular GP, call 1300 Dr To Me for an after-hours home doctor visit at the comfort of your home. It is especially important for people over 65, young children, pregnant women, and people with other chronic medical problems to seek medical attention for flu-like symptoms, as these groups are at the highest risk for developing complications from the flu. Please note that our after hours home doctors in Perth do not prescribe anti-biotic medications for viral illnesses.
Disclaimer: 1300 Dr To Me provides free health information blogs for the community to increase awareness on health & medical topics. The information in this article is educative and does not constitute diagnosis. Please consult a doctor, or request an urgent after hours home doctor visit should you or your family members experience any flu symptoms.