Common signs and symptoms of the flu include:
Fever over 100 F (38 C)
Aching muscles, especially in your back, arms and legs
Chills and sweats
Fatigue and weakness
Initially, the flu may seem like a common cold with a runny nose, sneezing, and sore throat. But colds usually develop slowly, whereas the flu tends to come on suddenly. And although a cold can be a nuisance, you usually feel much worse with the flu.
When to see a doctor
Most people who get the flu can treat themselves at home and often don't need to see a doctor. If you do come down with the flu, these measures may help ease your symptoms:
Drink plenty of liquids. Choose water, juice, and warm soups to prevent dehydration. Drink enough liquid so that your urine is clear or pale yellow.
Rest. Get more sleep to help your immune system fight infection.
Consider pain relievers. Use an over-the-counter pain reliever, such as acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin IB, others), to combat the achiness associated with influenza. Don't give aspirin to children or teens because of the risk of Reye's syndrome, a rare, but potentially fatal disease.
Taking antiviral drugs within the first 48 hours after you first notice symptoms may reduce the length of your illness and help prevent more serious problems. may help ease your symptoms:
If you have flu symptoms and are at risk of complications, see your doctor right away. Factors that may increase your risk of developing influenza complications include:
Age. Seasonal influenza tends to target young children and people over 65.
Weakened immune system. Cancer treatments, anti-rejection drugs, corticosteroids, and HIV/AIDS can weaken your immune system. This can make it easier for you to catch influenza and may also increase your risk of developing complications.
Chronic illnesses. Chronic conditions, such as asthma, diabetes, or heart problems, may increase your risk of influenza complications.
Pregnancy. Pregnant women are more likely to develop influenza complications, particularly in the second and third trimesters.
How Flu Spreads
People with flu can spread it to others up to about 6 feet away. Most experts think that flu viruses are spread mainly by droplets made when people with flu cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs. Less often, a person might also get flu by touching a surface or object that has flu virus on it and then touching their own mouth or nose.
When Are You Contagious?
Most healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5 to 7 days after becoming sick. Children may pass the virus for longer than 7 days. Symptoms start 1 to 4 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.
Stay home when sick!
To avoid this, people should stay away from sick people and stay home if sick. It also is important to wash hands often with soap and water or use an alcohol-based hand rub. Linens, eating utensils, and dishes belonging to those who are sick should not be shared without washing thoroughly first. They do not need to be cleaned separately. Frequently touched surfaces should be cleaned and disinfected at home, work, and school, especially if someone is ill.
How long do cold and flu germs stay alive?
It varies, depending partly on where the germ-laden droplets fall. Experiments with specific cold and flu germs have shown potential survival times ranging from a few minutes to 48 hours or more.
Germs generally remain active longer on stainless steel, plastic, and similar hard surfaces than on fabric and other soft surfaces. Other factors, such as the amount of virus deposited on a surface and the temperature and humidity of the environment, also have effects on how long cold and flu germs stay active outside the body.
It's easy to catch the flu or a cold from rubbing your nose after handling an object an infected person sneezed on a few moments ago. But personal contact with an infected person — a handshake, for example — is the most common way these germs spread.
The best way to avoid becoming infected with a cold or flu virus is to wash your hands frequently with soap and water or with an alcohol-based sanitizer. Also, avoid rubbing your eyes or biting your nails. Most importantly — get a flu vaccine every year.
Mayo Clinic 1/5/15