Seasonal Influenza (Flu)

Seasonal Influenza (more commonly known as Flu), is a contagious respiratory illness that primarily infects the nose and throat and is caused by three virus types in humans (influenza A, B, and C). Influenza infection sickens some people more than others depending on age and health status. On average, seasonal flu causes 50-60 million infections and illnesses, 25 million physician visits, 200,000 hospitalizations and 36,000 deaths each year in the United States alone.

Talking, singing, coughing and sneezing all produce tiny aerosolized or airborne droplets of potentially infectious material. Transmission of flu virus occurs when an uninfected person inhales the aerosolized secretions of a sick person. The virus can also be introduced to the nose or mouth after touching contaminated surfaces where the virus can survive for as little as 30 minutes to as long as 48 hours depending on the surface and environmental factors. The incubation period from exposure to onset of symptoms is generally 1 – 4 days and transmission to others is possible for approximately one day prior to onset of symptoms and for a week or longer after symptom onset.

Common symptoms include fever, chills, cough, headache, muscle and joint pain, fatigue, sore throat and runny or stuffy nose. Most people will recover from the flu within a few days; however, some may experience complications including sinus and ear infections, pneumonia, inflammation of the heart, brain or muscles, organ failure, sepsis and death. People 65 and older, children younger than 5, pregnant women and people with chronic health conditions or compromised immune systems are at higher risk of developing complications from flu infection. Antiviral drugs (i.e. Tamaflu) can lessen the severity and duration of flu symptoms and reduce the risk of flu related complications especially when it is taken within the first 2 days of illness onset.

Preventing illness caused by flu viruses is complicated by the fact that circulating flu viruses vary season to season and all influenza viruses undergo frequent genetic changes. Current influenza vaccines stimulate a protective immune response only to the strains included in the vaccine. These immune responses may not protect us from illness caused by new or different strains. This is why flu vaccines must be updated each year, why annual vaccination is recommended, any why flu vaccines don’t always prevent the flu.

In spite of these limitations, the most effective way to prevent seasonal flu is yearly vaccination. Flu vaccines are recommended for everyone 6 months and older, and greatly reduce the number and severity of illnesses, doctors’ visits, hospitalizations and deaths associated with the seasonal flu.

Researchers including Dr. Kawsar Talaat at the Center for Immunization Research, are working to develop a better flu vaccine - one that is capable of providing long-lasting protection against many strains of the flu virus even as they change or mutate over time. Such a vaccine may eliminate the need for annual vaccination to protect against seasonal influenza and could provide protection against newly emerging flu strains, including those that could cause a flu pandemic.