Fever, chills, cough, body aches and more are some of the symptoms of influenza, or often called the flu. It is caused by the influenza virus, which is a microorganism and is so small, you need a powerful microscope to see it. The flu infects the respiratory system, which is made up of the nasal passages, larynx, trachea, bronchial tubes, and lungs. The system, when working properly, allows a person to breathe and exchange oxygen and carbon dioxide throughout the body. In most cases when the respiratory system is not working properly, a person may simply have a common cold, but other times it may be the flu or influenza virus.
There are two main types of flu or the influenza virus called Influenza A and Influenza B. Influenza A is the group that most commonly causes illnesses in humans and is broken down into H and N subtypes, with 16 H subtypes and 9 N subtypes. The most contagious combinations causing nearly all outbreaks of the flu are H1N1, H2N2, H3N2. The strains are also named using the origin, geographical location, strain number, and the year of discovery of the virus. Nearly all major flu pandemics (spreads worldwide) in modern history have been caused by Influenza A.
Influenza B is less common but may still cause outbreaks of seasonal flu and have similar symptoms. The virus is not broken down into subtypes but by individual strains. When either influenza virus attacks the respiratory system, the symptoms include a high fever usually over 100°F, a cough, sore throat, stuffy or a runny nose, muscle pain, and weakness. The flu is a contagious illness meaning it can be spread from person to person by coughing and sneezing.
The virus can easily spread through the air and onto surfaces. When a person coughs or sneezes, virus-containing droplets from the person's mouth travel through the air and can be breathed in by another person or the droplets land on surfaces.
In addition, if a person with the flu sneezes or coughs into their hands and then touches something, the virus will remain on that item for a long time. A person who would touch the surface later could get the virus on their hand, touch their mouth, nose, or eyes, and then the virus could enter their body and could get the flu as well.
About every 10 years, the flu virus goes through major changes and many people can get severe cases. The large-scale outbreaks are called epidemics, and when they are worldwide, they are called pandemics. For example, the swine flu outbreak in 2009-2010 was epidemic and pandemic.
The body of the person who is exposed to the flu virus will go through an incubation period. First, once the person is exposed, the virus tries to invade a cell in your respiratory system. Once it gets into a cell it multiplies rapidly and clones itself many times while damaging the host cell. The newly-made viruses leave the damaged cell and begin invading other healthy cells. The process continues, and the virus spreads quickly throughout the body.
The incubation period may last two or more days to reproduce enough leading to the appearance of a variety of symptoms. A person can spread the virus to others during the incubation period, and then spread it about 5 to 7 days after they first get the symptoms.
In the U.S., the flu season is usually between October and May when millions of people come down with the flu each year. People of all age groups get the flu, but kids get the flu most often. Most likely, getting the flu is not serious, but older adults and young children and people with other medical conditions often become more seriously ill. In some cases, the flu strain could be much worse and can cause death.
People who do get the flu should stay home from work or school, rest, and drink lots of liquids, which includes drinks without caffeine. Sometimes medications like acetaminophen or ibuprofen can help with fever and aches, but it is important not to take aspirin, which can make matters worse. In addition, antibiotics usually do not work on the virus and will not help someone get better.
The best prevention of the flu is a vaccine. A flu vaccine is available as a shot and contains dead flu viruses. The body is tricked into believing it has the real flu and it makes new antibodies to fight off an infection if the person comes in contact with the live or real flu virus. Most people do not have a negative reaction to the flu vaccine but may notice a fever, sore muscles, and tiredness.
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