700 Children's® – A Blog by Pediatric Experts

Flu Complications: Risk Factors, Symptoms and Prevention

Jan 21, 2020
Child laying under a blanket, mom's hand placed on child's forehead

It's that time of year: flu season! The influenza virus causes a host of symptoms including high fever, headache, body ache, nasal congestion, cough, sore throat and vomiting. While these symptoms can be severe and long-lasting, the bigger (and sometimes life-threatening) problem with the flu are the complications that arise during the infection.

Some people have a higher risk of developing flu-related complications. This includes children under two years of age, the elderly, people with chronic medical conditions like asthma and heart disease and those with weakened immune systems.

So, what sort of complications are we talking about?

Pneumonia and Other Bacterial Infections

The immune system uses a lot of energy and resources in its long-lasting fight with the flu. This allows our normal mouth bacteria to go unchecked and provides opportunity for them to migrate down into the lungs and up into the ears and sinuses. While ear and sinus infections are easily treated with antibiotics, pneumonia presents more of a problem. In fact, most flu-related deaths are caused by this very serious complication.

Signs of pneumonia include fever that lasts more than three days, fever that goes away for a couple days and then returns, worsening cough or difficulty breathing. Anyone with the flu who develops these symptoms should be seen by a medical provider right away.

Bacteria from pneumonia can spread to the blood and cause a very dangerous condition called sepsis. Urinary tract infections (UTI) are also common with flu, especially in girls. Peeing rinses the bladder of skin bacteria that has made its way inside. Influenza zaps energy and appetite, so those with the flu drink and pee less, which can lead to a UTI. More reason to seek help when fever does not go away or returns!

Vomiting and Dehydration

Vomiting does not always occur with the flu, but when it does, dehydration can happen in a hurry. There are good medications to stop vomiting, but they are only available by prescription. Anyone who vomits more than a few times or who is not making urine at regular intervals needs to be evaluated by a medical provider. If dehydration is present, intravenous (IV) fluids might be needed.

Nervous System Problems

This is a rare complication of the flu, but one that is extremely serious. Sometimes the antibodies our immune system uses to fight the flu begin attacking other parts of the body. When antibodies attack nerves, progressive weakness called Guillain-Barré Syndrome can occur. Signals from the brain and spinal cord are not able to reach muscles, including those that keep us breathing.

Anyone who develops severe weakness, difficulty walking or difficulty breathing should seek emergency medical help right away.

Preventing Flu Complications

If these complications of the flu sound scary, that's because they are! This is why doctors and nurses are passionate about their patients getting flu shots. The flu vaccine may not be 100% effective in preventing flu illness, but it does a very good job of preventing flu hospitalizations and death. If you haven’t had a flu vaccine, it's not too late to get one. The flu will be around the rest of the winter and it can make you sick more than once each season.

Those at high risk for flu complications (see above) should visit their medical provider at the first sign of high fever during flu season. Antiviral medication can decrease the risk of complications, but it must be started within a day or two of fever onset to have the best chance of working.

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Featured Expert

Nationwide Children's Hospital Medical Professional
Mike Patrick, MD
Emergency Medicine; Host of PediaCast

Dr. Mike Patrick is an Assistant Professor of Pediatrics at the Ohio State University College of Medicine and Medical Director of Interactive Media for Nationwide Children's Hospital. Since 2006, he has hosted the award-winning PediaCast, a pediatric podcast for parents. Dr. Mike also produces a national podcast for healthcare providers—PediaCast CME, which explores general pediatric and faculty development topics and offers free AMA PRA Category 1 Credit™ to listeners.

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700 Children’s® features the most current pediatric health care information and research from our pediatric experts – physicians and specialists who have seen it all. Many of them are parents and bring a special understanding to what our patients and families experience. If you have a child – or care for a child – 700 Children’s was created especially for you.