Influenza, commonly known as the flu, is a respiratory illness caused by viruses affecting the nose, throat, and sometimes the lungs. It can range from mild to severe. Many wonder about flu transmission, especially if they’ve recently recovered or been in contact with someone they may have infected. This article addresses a common question: Can you get the flu from someone you gave it to?
How the Flu Virus Spreads
The flu virus primarily spreads through tiny droplets released when an infected person coughs, sneezes, or talks. These droplets can land in the mouths or noses of nearby individuals or be inhaled. Less commonly, one might contract the flu by touching a contaminated surface or object and then their own mouth, nose, or eyes.
People infected with the flu can spread the virus even before symptoms appear, typically one day prior to onset. The incubation period, between exposure and symptom development, usually ranges from one to four days, averaging two days. Individuals are most contagious during the first three to four days of illness.
How Your Body Fights the Flu
When the influenza virus enters the body, the immune system initiates a response. This involves identifying viral particles and producing specific proteins called antibodies. These antibodies recognize and neutralize the particular flu strain that caused the infection.
Once a person recovers from the flu, these antibodies provide protection against future infections with the exact same or very similar strains. This immunity is strain-specific; for instance, antibodies against one influenza A subtype do not necessarily protect against another. While antibodies can persist for a long time against a specific strain, this immunity can wane over several months to a year.
Understanding Flu Re-infection and Different Strains
It is unlikely to contract the exact same flu strain back from someone you infected, especially soon after recovery. This is because your immune system develops antibodies that protect against that specific strain. However, getting the flu again is possible under different circumstances.
The influenza virus is not a single entity; multiple strains circulate during each flu season. Immunity to one strain does not protect against others, meaning you could be infected by a different circulating strain. Flu viruses also continually change through processes known as antigenic drift and antigenic shift. Antigenic drift involves small, gradual mutations in the virus’s genes, leading to subtle changes in its surface proteins, which can make previous immunity less effective. Antigenic shift is a more abrupt and major change, typically in influenza A viruses, leading to a new subtype the human immune system may not recognize, potentially causing widespread illness. Immunity can also wane over time, or a person’s immune system might be weakened, increasing susceptibility to re-infection even with similar strains after a longer period.