Influenza
Influenza, more commonly known as the flu, is a viral illness that affects the respiratory tract. There are 3 types of influenza viruses: influenza A, B, and C. Each of these has several subtypes. All these forms of the virus mutate (change their genes slightly) and vary from year to year. This is why it is possible for the same person to have repeated episodes of the flu. Flu is usually transmitted from person to person through drops of respiratory discharge. Symptoms of the flu can include, fever, cough, chest pain, nasal discharge headaches, malise, or a vague feeling of illness, muscle pain, chills, excessive sweating, nausea, vomiting, and stiffness. The flu strikes about 7 out of 1,000 people. It is highly contagious.
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