Medically Approved

Flu symptoms, diagnosis, and prevention

Person with the flu

Optum Perks Author

By Optum Perks Author

The Flu, short for influenza, is a common contagious viral illness that can be spread directly or indirectly. It is spread directly from one person to another through airborne droplets produced by coughing or sneezing. It may also be spread indirectly when contaminated droplets land on a surface that is subsequently touched by an uninfected person. The incubation period for someone with the flu is about one to four days, with the symptoms lasting up to fourteen days. It is caused by viruses that infect the respiratory system.

The number of seasonal flu-associated deaths varies from one year to another in the United States. This is primarily because flu seasons are unpredictable and often fluctuate in length and severity. According to the CDC, from the 1976-1977 season to the 2006-2007 flu season, there is an estimated low of 3,000 and a high of about 49,000 flu-associated deaths.

You can catch flu year-round, but it is most common during winter, which is why it is also referred to as seasonal flu. Most individuals who contract a seasonal flu recover completely in one or two weeks, but it may develop into life-threatening health conditions such as pneumonia.


The Flu is caused by a virus, however, it differs from the ones that cause a cold. The symptoms are sudden and tend to be more severe and longer lasting.


The main symptoms of flu include:

  • A dry, chesty cough
  • A headache
  • A high temperature fever of 100F or above
  • General aches and pains
  • Tiredness and weakness
  • Nausea and vomiting
  • Loss of appetite
  • Difficulty sleeping
  • Chills
  • Abdominal pain or diarrhea

You may also experience cold-like symptoms such as a runny nose, blocked nose, sore throat and sneezing. These symptoms are not as severe as the other symptoms indicated above.


The illness can make you feel unwell and exhausted to an extent of confining you to bed rest until the symptoms lighten.

Diagnosis and treatment

The diagnosis for the flu involves physical examination, laboratory tests and a look into the patient's medical history. If you feel healthy and fit, you don't necessarily have to visit a doctor if you have flu-like symptoms.


It is recommended that you rest at home until you feel better, while drinking plenty of water. You also want to keep warm and take non-opioid pain medications if necessary. However, it is important to check with your doctor if you are at a higher risk of contracting severe flu symptoms than the normal healthy population.

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Visit your doctor if:

  • You are pregnant
  • Your symptoms are worsening over time
  • You are over sixty-five years old
  • You have a long-term medical condition such as lung disease, heart disease or diabetes
  • You develop shortness of breath, chest pain, or difficulty in breathing
  • You have a weakened immune system due to HIV or chemotherapy


It is estimated that an average of five to twenty percent of the population in the United States gets the flu each year, with more than 200,000 people hospitalized from seasonal flu-related complications. Getting a flu shot is the best protection against the flu. You can, however, get prescriptions from a doctor or buy over the counter medications to treat the flu.


The effectiveness of the flu shots may vary from year to year as flu causing strains also vary from one year to the other. This is also seen with flu medications that are frequently changing and improving much like the virus each year.

The influenza type-A virus undergoes frequent antigenic changes that require new vaccines. Therefore, a new flu shot is needed every year.

History of the flu shot

A flu shot is a seasonal vaccine given in the arm with a needle to protect against the three influenza viruses. There are several flu vaccine options, including the trivalent and the quadrivalent vaccines.


The CDC's Advisory Committee on Immunization practices voted for a universal flu vaccination in the U.S. to further its protection against the flu for more people. This recommendation has been in place since February 24th, 2010. You can get a flu shot from one of the many doctors in their offices, clinics, health departments, pharmacies and college health centers, urgent care clinic as well as by a number of employers and in schools.