Getting well from the flu is generally not contagious in the short term; however, you can be reinfected after a change in the type of flu virus.
After an influenza virus infection, antibodies to the corresponding influenza virus are usually present in the body, but after re-exposure to this type of virus, re-infection is usually not possible.
However, influenza viruses are prone to mutation, and the influenza viruses are divided into influenza A and influenza B. The specific types of influenza viruses are different, and the types that are prevalent vary from year to year, so after being infected with influenza viruses, reinfection can occur if the types that are prevalent change.
Influenza viruses are contagious quickly, so people with low immunity or underlying medical conditions can be prevented by getting the flu vaccine before the onset of each year’s flu.