Influenza

Overview Flu (influenza) is an infection of the nose, throat and lungs, which are part of the respiratory system. Influenza is commonly called the flu, but it's not the same as stomach "flu" viruses that cause diarrhea and vomiting. Most people with the flu get better on their own. But sometimes, influenza and its complications can be deadly. People at higher risk of developing flu complications include: • Young children under age 2 • Adults older than age 65 • Residents of nursing homes and other long-term care facilities • People who are pregnant or plan to be pregnant during flu season • People with weakened immune systems • American Indians or Alaska Natives • People who have chronic illnesses, such as asthma, heart disease, kidney disease, liver disease and diabetes • People with a body mass index (BMI) of 40 or higher Although the annual influenza vaccine isn't 100% effective, it reduces the chances of having severe complications from infection. Symptoms At first, the flu may seem like a common cold with a runny nose, sneezing and sore throat. Colds usually develop slowly. But the flu tends to come on suddenly. And while a cold can be miserable, you usually feel much worse with the flu. Common symptoms of the flu include: • Fever • Aching muscles • Chills and sweats • Headache • Dry, persistent cough • Shortness of breath • Tiredness and weakness • Runny or stuffy nose • Sore throat • Eye pain • Vomiting and diarrhea, but this is more common in children than adults R...

The flu is a common respiratory illness you get from the influenza virus. Symptoms often include fever, head and body aches, coughing and a stuffy or runny nose. You’re at risk for serious complications if you have an underlying health condition or are pregnant. Getting vaccinated every year is the best way to avoid getting sick with the flu. Overview The flu, common cold and COVID-19 have similar symptoms. The flu and COVID-19 can be severe, but colds rarely are. What is the flu (influenza)? The flu is an illness you get from the influenza virus. It causes symptoms like head and body aches, sore throat, fever and respiratory symptoms, which can be severe. Flu is most common in winter months, when many people can get sick at once (an epidemic). When is flu season? Flu season — when cases of the flu go up dramatically — in the Northern Hemisphere (which includes the U.S.) is October through May. The highest number of cases (peak) usually happen between December and February. How common is the flu? The flu is one of the most common What is the difference between the flu and the common cold? The flu and the common cold can have similar symptoms, like runny nose and cough. But cold symptoms are usually mild and flu symptoms can be severe and lead to serious complications. Different viruses cause colds and the flu. How do I know if I have the flu or COVID-19? Since they have similar symptoms, the only way to know for sure if you have the flu or COVID-19 is to get tested. They b...

Type A influenza is a common infection that can cause widespread flu outbreaks. It can cause fever, body aches, chills, fatigue, and other symptoms. Common symptoms of type A infection can be confused with other conditions. While in some milder cases the flu can resolve on its own without significant symptoms, severe cases of type A influenza can be life-threatening. Types A and B influenza are the more common forms of this infection, routinely causing seasonal outbreaks. Type C influenza usually only causes mild respiratory infections. Type B influenza can be just as severe as type A influenza but is less common throughout the flu season compared to type A. Humans are the natural host for type B infection. Type B viruses mutate much slower than type A infections and are categorized by strains, but not subtypes. The B virus strains take longer for their genetic makeup to change than influenza A. This drastically reduces the risk of a widespread pandemic due to type B influenza. Type A influenza can be dangerous and is known to cause outbreaks and increase your risk of disease. Unlike a type B infection, type A viruses are categorized by subtypes and strains. Influenza A mutates faster than influenza B, but both viruses are always changing, creating new strains from one flu season to the next. Past flu vaccinations will not prevent infection from a new strain. Wild birds are the natural hosts for a type A virus, also called avian flu and bird flu. This infection can also sp...

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Overview Seasonal influenza is an acute respiratory infection caused by influenza viruses which circulate in all parts of the world.There are 4 types of influenza viruses, types A, B, C and D. Influenza A and B viruses circulate and cause seasonal epidemics of disease. • Influenza A viruses are further classified into subtypes according to the combinations of the hemagglutinin (HA) and the neuraminidase (NA), the proteins on the surface of the virus. Currently circulating in humans are subtype A(H1N1) and A(H3N2) influenza viruses. The A(H1N1) is also written as A(H1N1)pdm09 as it caused the pandemic in 2009 and subsequently replaced the seasonal influenza A(H1N1) virus which had circulated prior to 2009. Only influenza type A viruses are known to have caused pandemics. • Influenza B viruses are not classified into subtypes, but can be broken down into lineages. Currently circulating influenza type B viruses belong to either B/Yamagata or B/Victoria lineage. • Influenza C virus is detected less frequently and usually causes mild infections, thus does not present public health importance. • Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people. Signs and symptoms Seasonal influenza is characterized by a sudden onset of fever, cough (usually dry), headache, muscle and joint pain, severe malaise (feeling unwell), sore throat and a runny nose. The cough can be severe and can last 2 or more weeks. Most people recover from fever and o...