The Ways to Know If Your Child Has the Flu

Influenza, or flu, is an infection caused by the flu virus.

It can be tricky to distinguish between flu symptoms and symptoms of a bad cold or another virus. Many other viral illnesses can cause "flu-like symptoms," although they're usually more intense than regular cold symptoms.

Mother feeling sick daughter's forehead
Alain Daussin / Getty Images

A few specific symptoms to watch out for are a high fever, muscle aches and pains, lethargy, headaches, dry cough, sore throat, and runny nose. Nausea, vomiting, and diarrhea are less-common symptoms of the flu. These symptoms can last for a few days to a few weeks.

The influenza virus can cause croup, bronchiolitis, ear infections, and pneumonia.

The flu is very contagious. In general, people with the flu are contagious and can make others sick beginning a few days before they even start having flu symptoms themselves and for up to five to seven days after getting sick. Kids can usually go back to school or daycare once they are free of fever for twenty-four hours, though.

Sometimes the only way to tell the difference between a cold and the flu is by doing a flu test. This can be important because flu medicines, like Tamiflu, can help to decrease the severity of flu symptoms and help your high-risk child get better sooner.

Flu Tests

Rapid flu tests are popular with pediatricians and parents. With this flu test, a simple nasopharyngeal cotton swab in your child's nose can usually determine within 15 minutes if he has the flu.

Unfortunately, although they are commonly used, these flu tests have some downsides, including a high rate of false negatives during the peak of flu season and some false positives when flu activity is low.

According to the Centers for Disease Control, a flu test is not needed for all patients with suspected flu. Instead, once it is known that flu is in the area, the diagnosis can usually be made clinically, based on the child's symptoms. A flu test may be helpful if a child is hospitalized with severe flu symptoms, if he has other high-risk medical problems, or if the flu test results might influence infection control practices of other children.

In addition to the rapid flu test, other flu tests can include flu virus culture, direct fluorescent antibody tests, and PCR molecular tests. Although usually more accurate, it can take much longer to get results using one of these other flu tests, from several hours to several days.

Flu Treatments

Unlike many other viruses, some medications can help to treat the flu, including Tamiflu (oseltamivir), Relenza (zanamivir), and Xofluza (baloxavir marboxil).

Tamiflu is available in capsule and suspension form, Xofluza in tablet and suspension, and Relenza as a dry powder inhaler.

When given within 48 hours of the start of flu symptoms, these prescription flu medicines can help prevent serious flu complications, shorten the period of illness by one or two days, and reduce the length of stay for hospitalized patients.

Kids who recently had the FluMist nasal spray flu vaccine may test positive on a flu test for at least seven days. The possibility of increased resistance with overuse, the high price of flu medicines, poor taste of liquid Tamiflu, and concerns about Tamiflu side effects are good reasons to only use antiviral flu medicines when they are really needed.

Most people don't need these flu treatments, though. The CDC only recommends routine use of antiviral flu medications for people who are at risk for serious complications from the flu, including children younger than 5, adults 65 years and older, pregnant women, people with many chronic medical problems, and residents of nursing homes and other facilities. Children and teens receiving long-term aspirin therapy should also avoid flu treatments. Although you should never give kids aspirin, it is especially important to avoid aspirin when your kids have the flu, because it has been linked to Reyes syndrome.

Most importantly, if your kids have the flu and didn't get a flu vaccine this year, consider having them vaccinated next year. That will decrease the chances that they get sick with the flu again.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Smith DK, Mcdermott AJ, Sullivan JF. Croup: Diagnosis and Management. Am Fam Physician. 2018;97(9):575-580.

  3. Justice NA, Le JK. Bronchiolitis. In: StatPearls [Internet]. 2019 Jan-. 

  4. Influenza Signs and Symptoms and the Role of Laboratory Diagnostics. Centers for Disease Control and Prevention. October 2016.

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By Vincent Iannelli, MD
 Vincent Iannelli, MD, is a board-certified pediatrician and fellow of the American Academy of Pediatrics. Dr. Iannelli has cared for children for more than 20 years.