Influenza: How to prevent and treat a serious infection

This fall is different than any other before it. Back-to-school is different, professional and college sports are different, and many of the seasonal rituals are upended thanks to COVID-19. But what isn’t different is the return of influenza or the flu. The flu is more than a bad cold. Although many people who get the flu recover with rest and fluids, thousands of Americans die from this illness each year, and millions are sick enough to miss work or school. Influenza is serious — but it can be prevented and treated.

This flu season is complicated by worries about COVID-19. The same measures that help prevent the spread of the coronavirus — frequent and thorough handwashing, wearing a mask, not touching your face, coughing and sneezing into a tissue or your elbow, avoiding people who are sick, and staying away from others if you're sick — also help to protect against spread of the flu.

Meet the flu bug

There are many influenza viruses. Nearly all cases of the flu are caused by human strains of the influenza A or B virus. Influenza A is the more serious strain. Because flu viruses change from year to year, having had the flu — or a flu shot — in a previous year won’t protect you this year. That's why you need to get a new flu shot each year.

It is important to note that flu viruses are distinct from the coronaviruses that cause illnesses like COVID-19.  

Influenza epidemics

In the U.S., the flu season runs roughly from Thanksgiving to Easter, with most cases occurring in the dead of winter. The Centers for Disease Control and Prevention estimated that during the 2018–2019 flu season an estimated 35.5 million people came down with the flu. Of these people over 16 million had to see their doctors, and over 30,000 people died from the flu.

Influenza is highly contagious

As a respiratory virus, influenza spreads on tiny droplets that spew into the air when you cough, sneeze, or simply exhale. People close at hand are the most likely to catch the flu, which is why the infection spreads so quickly through families, health care facilities, and other places where people live or work close to each other. The influenza virus can also be spread by hand-to-hand contact.

Influenza symptoms

Influenza hits fast. After an incubation period of just one to two days, the influenza symptoms start abruptly. Most people run a fever, and high temperatures in the 103 F to 104 F range are common. Nearly everyone has a runny nose and sore throat, but unlike ordinary colds, the flu also produces a hacking, dry cough. Muscle and joint aches can be severe. Headache, burning eyes, weakness, and extreme fatigue add to the misery.

In most cases, the high fever and severe distress settle down in two to five days, but the cough can linger for a week or two and the fatigue even longer.

Influenza complications

The most serious — and deadly — complication is pneumonia. Young children, senior citizens, and people with chronic illnesses are at greatest risk. That's why they have the greatest need for preventive vaccinations and medical treatments.

In some cases, pneumonia is caused by the flu virus itself. It's a particularly deadly problem that begins early in the infection and progresses rapidly, with a severe dry cough and shortness of breath. Bacterial pneumonia is more common but more easily treated. It starts later, after a person seems to be on the mend. The fever returns and the cough increases, this time with thick, pus-laden sputum (phlegm).

Other flu complications can include asthma attacks, ear infections, bronchitis, sinusitis, inflammation of the heart or other muscles, and inflammation of the nervous system.

COVID-19 most often causes no or minimal symptoms similar to what a person feels with a cold. But anyone infected with this coronavirus can have symptoms that are just like influenza.

Flu Diagnosis

Your doctor will recognize the flu based on your symptoms, the season, and if the flu is going around the community. But milder cases of the flu can resemble other respiratory infections that also strike in the winter. You can use the information in the table "Is it the flu?" to see if your symptoms are likely to be the flu or a less serious problem — and to start thinking about what to do. And remember to consult your doctor for personal diagnosis and treatment.

While sometimes it is pretty clear that a person has the flu, doctors may recommend a  flu test. Most often, a rapid flu test can be done right in the office or clinic. The result comes back within 15 minutes. A positive test almost always confirms the flu. However, sometimes the test is negative despite the person having influenza. In that case the sample may be sent out for special flu testing. Blood tests, chest x-rays, and other studies may be needed if complications develop.

Flu prevention: Hygiene

Whether or not you've had a flu shot this year, a few simple precautions can help protect you and your family:

• Wash your hands. Use ordinary soap and water or alcohol-based hand rubs and gels. Take extra time cleaning your hands after any contact with folks who have flu-like symptoms.
• Keep your distance. The flu is most contagious within three feet of someone who has it. If your community is hard-hit this winter, try to minimize the time you spend in crowded places.
• Wear a mask if you are in a high-risk group and you can't avoid getting up-close and personal with possible flu victims. Be sure your mask fits well. Keep it free of saliva and dry, and change it periodically.
• Protect others. Don't go to work or school if you have the flu. Use a tissue to cover your mouth when you sneeze or cough, and dispose of it properly. If a tissue isn't handy, sneeze into your elbow, not your hands. Wear a mask if you have to go public, especially in health care facilities.

Flu prevention: Vaccination

New influenza vaccines are produced for every flu season; each protects against the main strains of influenza A and influenza B that are most likely headed our way. In the U.S., October and November are the ideal months to get the vaccine — but it isn't too late to get one in January or February. Children ages six months to eight years who have never been immunized need two doses, but one dose will suffice for all others.

The flu vaccine is given by injection. Depending on your age and whether you have a true egg allergy, your health care provider will recommend the specific vaccine type. Side effects are mild and uncommon, amounting to a slightly sore arm or a slight fever.

Everyone above six months of age should get a yearly flu vaccine. Here is a list of high-priority vaccine candidates:

• All children ages six months to four years
• All adults age 50 and older
• Children and adolescents ages 6 months to 18 years who receive long-term aspirin therapy
• Women who are likely to be pregnant during the flu season
• People who have asthma, diabetes, or chronic diseases of their lungs, heart, blood, kidneys, or liver
• People who have illnesses or take medications that impair the immune system
• Residents of chronic-care facilities
• Health care personnel and child care providers
• Caregivers and household contacts of persons with medical conditions that put them at risk

Flu prevention and treatment: Medications

Antibiotics don't work against viruses, including influenza. But even though there are no medications for ordinary viruses, special prescription drugs can be used to treat or prevent the flu. They don't cure the flu, but they can ease and shorten the illness if started within the first 36 hours of flu symptoms. Two of them can also be used to prevent influenza in unvaccinated persons who are exposed to the infection.

Oseltamivir (Tamiflu) is available in tablet form. It is approved for treatment in patients two weeks of age and older and for prevention above one year of age. Side effects may include nausea and vomiting; behavioral abnormalities have also been reported.

Zanamivir (Relenza) is administered by inhalation from a nebulizer. It is approved for prevention in people age five and older and for treatment in people age seven and older. Side effects may include wheezing, nausea, and vomiting; behavioral abnormalities have also been reported.

Baloxavir marboxil (XOFLUZA) is take a single oral dose. It is approved for the treatment of people ages 12 years and older. Potential side effects include rash, severe allergic reaction (rarely), nausea and diarrhea.

Peramivir is given as a single intravenous dose, approved for treatment of influenza. It may cause diarrhea, severe allergic reactions (rarely), and behavioral abnormalities.

If you get the flu and can start treatment within about 36 hours, ask your doctor about an antiviral drug. Whether or not you take an antiviral drug, be sure to get lots of rest and drink plenty of fluids. Acetaminophen (Tylenol and other brands) or ibuprofen (Advil, Motrin, generics) can help ease fever and aches. Be careful when using products that treat multiple symptoms. It is easy to accidentally take unsafe doses of acetaminophen. Aspirin is also effective, but shouldn't be used by anyone under 18.

Be sure to contact your doctor right away if you develop chest pain, shortness of breath, confusion or difficulty staying hydrated.

Respect the flu

Although influenza is a serious infection, it doesn't get the respect it deserves. Don't make the mistake of dismissing the flu as "just a virus." Instead, get an immunization each fall and take simple precautions to protect yourself and your family during influenza outbreaks. And if you get the flu, ask your doctor if medication might speed your recovery.