Seasonal influenza (also known as the flu) is a contagious respiratory illness caused by flu viruses. It can cause mild to severe illness, and at times can lead to death. The flu is different from a cold . The flu usually comes on suddenly and may include these symptoms:
- Fever (usually high)
- Extreme tiredness
- Dry cough
- Sore throat
- Runny or stuffy nose
- Muscle aches
- Stomach symptoms, such as nausea, vomiting, and diarrhea, also can occur but are more common in children than adults
These symptoms are usually referred to as "flu-like symptoms."
The Flu Is Contagious
Most healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5-7 days after becoming sick. Children may pass the virus for longer than seven days. Symptoms start one to four days after the virus enters the body. That means that you may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick. Some persons can be infected with the flu virus but have no symptoms. During this time, those persons may still spread the virus to others.
How The Flu Spreads
The main way that influenza viruses are thought to spread is from person to person in respiratory droplets of coughs and sneezes. (This is called "droplet spread.") This can happen when droplets from a cough or sneeze of an infected person are propelled through the air and deposited on the mouth or nose of people nearby. Influenza viruses may also be spread when a person touches respiratory droplets on another person or an object and then touches their own mouth or nose (or someone else’s mouth or nose) before washing their hands. ( Cover Your Cough <pdf>)
Linens, eating utensils, and dishes belonging to those who are sick do not need to be cleaned separately, but importantly these items should not be shared without washing thoroughly first. Linens (such as bed sheets and towels) should be washed by using household laundry soap and tumbled dry on a hot setting. Individuals should avoid “hugging” laundry prior to washing it to prevent contaminating themselves. Individuals should wash their hands with soap and water immediately after handling dirty laundry. If soap and water are not available, they should use an alcohol-based hand rub* to clean their hands. Eating utensils should be washed either in a dishwasher or by hand with water and soap. ( Wash Your Hands <pdf>)
How To Know if You Have the Flu
Your respiratory illness might be the flu if you have sudden onset of body aches, high fever, and respiratory symptoms, and your illness occurs during the usual flu season in the Northern Hemisphere. However, during this time, other respiratory illnesses can cause similar symptoms to the flu. In addition, influenza can also occur outside of the typical flu season. It is impossible to tell for sure if you have the flu based on symptoms alone. Doctors can perform tests to see if you have the flu if you are in the first few days of your illness. Regardless of if you have influenza-like symptoms, it's best to take care of yourself .
At Risk Groups
Anyone can get the flu (even healthy people), and serious problems from influenza can happen at any age. Certain individuals are "high risk" and should talk to a health care provider about whether they need to be examined if they get influenza-like symptoms this season. They include:
- Children ages 6 months to 24 years (especially children under the age of 2 years old)
- People 65 and older
- Pregnant women
People with any chronic medical conditions that may increase risk of complications from influenza-like symptoms (such as asthma, diabetes, or heart disease)
Pneumonia, bronchitis, and sinus and ear infections are three examples of complications from flu. The flu can make chronic health problems worse. For example, people with asthma may experience asthma attacks while they have the flu, and people with chronic congestive heart failure may have worsening of this condition that is triggered by the flu.
*Information from CDC and Flu.gov.