Influenza, or flu, is a respiratory infection caused by a variety of flu viruses. The flu is a common catch-all term among the general public for a variety of illnesses, but it correctly applies only to the upper respiratory disease caused by the influenza virus.
Estimates are that between 15% and 40% of the population will develop illness from influenza every year. An average of about 36,000 people per year in the United States die from influenza, and 114,000 per year have to be admitted to the hospital as a result of influenza. Anyone can get the flu (even healthy people), and serious problems from influenza can happen at any age. People age 65 years and older, people of any age with chronic medical conditions, and very young children are more likely to get complications from influenza.
For the most current information about influenza in Florida, please see Florida's weekly surveillance report, the Flu Review.
Contagious vs. Non-Contagious Diseases
A contagious disease is a subset category of infectious diseases (or communicable diseases), which are easily transmitted by physical contact (hence the name-origin) with the person suffering the disease, or by their secretions or objects touched by them.
The non-contagious category of infectious / communicable diseases usually require a special mode of transmission between hosts. These include need for intermediate vector species (such as a mosquito for yellow fever), direct blood contact (such as transfusion or needle-sharing), or sexual contact (examples are AIDS and hepatitis B).
The boundary between contagious and non-contagious infectious diseases is not perfectly drawn, as illustrated classically by tuberculosis, which is clearly transmissible from person to person, but was not classically considered a contagious disease. In the present day, most sexually transmitted diseases are considered contagious, but only some of them are subject to medical isolation.