How Flu Viruses Can Change Flu viruses can change in two different ways—antigenic drift and antigenic shift. Transmission of Flu Viruses from Animals to People Flu A viruses also are found in many different animals, including ducks, chickens, pigs, horses, whales, and seals. Learn more, including about past flu pandemics. Images of Flu Viruses Graphics of generic flu viruses Human Serology and Flu CDC conducts human serology work to improve seasonal flu vaccines and prepare against future flu pandemics.
Antigenic Characterization of Flu Viruses CDC antigenically characterizes circulating flu viruses each year to monitor for changes and to help inform flu vaccine composition recommendations. What CDC Does. To receive weekly email updates about Seasonal Flu, enter your email address: Email Address. What's this? Preventing the flu and reducing the severity of flu illness and hospitalizations could also lessen the number of people needing to stay in the hospital.
This year's seasonal flu vaccine provides protection from the four influenza viruses that are expected to be the most common during the year's flu season. This year, the vaccine will be available as an injection and as a nasal spray. Avoid crowds. The flu spreads easily wherever people gather — in child care centers, schools, office buildings, auditoriums and public transportation. By avoiding crowds during peak flu season, you reduce your chances of infection.
Also avoid anyone who is sick. And if you're sick, stay home for at least 24 hours after your fever is gone so that you lessen your chance of infecting others. Your local health department and the CDC may suggest other precautions to reduce your risk of COVID or the flu if you haven't been fully vaccinated.
For example, you may need to practice social distancing physical distancing and stay at least 6 feet 2 meters from others outside your household. You may also need to wear a cloth face mask when indoors with people outside your household and when outdoors in crowded areas.
If you're fully vaccinated and are in an area with a high number of new COVID cases in the last week, the CDC also recommends wearing a mask indoors in public and outdoors in crowded areas or when you're in close contact with unvaccinated people.
Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission. Check out these best-sellers and special offers on books and newsletters from Mayo Clinic Press. This content does not have an English version. This content does not have an Arabic version. Overview Influenza is a viral infection that attacks your respiratory system — your nose, throat and lungs. More Information Flu: When to see a doctor? Request an Appointment at Mayo Clinic. Mayo Clinic Minute: Why getting vaccinated for the flu is doubly important this season.
More Information Flu shots Cold and flu viruses: How long can they live outside the body? High-dose flu vaccines: How are they different from other flu vaccines? Share on: Facebook Twitter. Show references Jameson JL, et al. In: Harrison's Principles of Internal Medicine. New York, N. Accessed July 13, Zachary KC. Flu is different from a cold.
Flu usually comes on suddenly. People who have flu often feel some or all of these symptoms:. Most experts believe that flu viruses spread mainly by tiny droplets made when people with flu cough, sneeze or talk.
These droplets can land in the mouths or noses of people who are nearby. Less often, a person might get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose or possibly their eyes. The same CID study external icon found that children are most likely to get sick from flu and that people 65 and older are least likely to get sick from influenza.
Median incidence values or attack rate by age group were 9. This means that children younger than 18 are more than twice as likely to develop a symptomatic flu infection than adults 65 and older. Influenza virus infection is so common that the number of people infected each season can only be estimated. These statistical estimations are based on CDC-measured flu hospitalization rates that are adjusted to produce an estimate of the total number of influenza infections in the United States for a given flu season.
The estimates for the number of infections are then divided by the census population to estimate the seasonal incidence or attack rate of influenza. Does seasonal incidence of influenza change based on the severity of flu season?
The proportion of people who get sick from flu varies. You may be able to spread flu to someone else before you know you are sick, as well as while you are sick. The time from when a person is exposed and infected with flu to when symptoms begin is about 2 days, but can range from about 1 to 4 days. Complications of flu can include bacterial pneumonia, ear infections, sinus infections and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes.
Anyone can get flu even healthy people , and serious problems related to flu can happen at any age, but some people are at high risk of developing serious flu-related complications if they get sick. This includes people 65 years and older, people of any age with certain chronic medical conditions such as asthma, diabetes, or heart disease , pregnant women, and children younger than 5 years.
The first and most important step in preventing flu is to get a flu vaccine each year. Flu vaccine has been shown to reduce flu related illnesses and the risk of serious flu complications that can result in hospitalization or even death.
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