Viral Myositis: Causes, symptoms, and care options
Key Takeaways:
- Viral myositis can affect kids' ability to walk a few days after viral infection
- The condition is often seen during an influenza infection
- Muscles get worn down from inflammation during viral myositis
- Hydration plays a huge role in helping kids recover from the condition
When a child suddenly refuses to walk days after recovering from the flu, it can be terrifying for parents, but doctors say a little-known condition called viral myositis is often the cause.
It’s a muscle condition most often seen in children during or shortly after common viral infections, especially influenza (the flu). While the condition can be alarming for parents, medical experts say it is usually temporary and treatable with proper care.
Mustafa Bakir, MD, a pediatric infectious disease specialist with OSF HealthCare, says viral myositis typically appears a few days after the onset of a viral illness.
What is viral myositis?
Viral myositis refers to inflammation of the muscles caused by a viral infection. A specific and more common form in children is known as benign acute childhood myositis (BACM).
“Benign acute childhood myositis (BACM) is more likely to be seen with influenza,” Dr. Bakir says.
In these cases, the virus can trigger muscle inflammation after the initial respiratory symptoms begin to improve.
“Viral myositis, oftentimes, starts with influenza and then begins to cause damage in the person's muscles, also known as muscle inflammation.”
Common symptoms and who is affected
Viral myositis most often affects the calf muscles and can significantly impact how a child walks.
“Calves are almost exclusively affected by viral myositis, as well as gait (walking pattern).”
Children may complain of sudden leg pain, stiffness or difficulty walking, sometimes refusing to walk altogether. The condition is most seen in younger kids.
“This is likely a benign condition, but it takes about three to seven days to heal. It's mostly seen in school-aged children between 4 and 7 years of age,” Dr. Bakir says. “Usually, it presents with this pain and gait problems. Patients usually are out of school for those days.”
Treatment and recovery
In most cases, viral myositis resolves on its own within about a week. Supportive care at home is often sufficient, with a strong focus on hydration and pain control.
“Fluid support is important to prevent kidney damage. Anti-inflammatory medications like ibuprofen both decrease the pain and inflammation,” Dr. Bakir says.
Encouraging children to drink water and electrolyte-containing fluids is especially important during recovery.
When to seek emergency care
While viral myositis is usually mild, some symptoms require urgent medical evaluation. Severe pain, inability to walk or extreme muscle tenderness may signal a more serious condition.
“We must differentiate severe myositis from benign acute childhood myositis. If the patient has very severe pain and can't walk, they must be seen in the emergency department,” Dr. Bakir says. “The physician will decide if this is serious, and if the patient needs to be admitted.”
In rare cases, viral infections can lead to rhabdomyolysis, a severe breakdown of muscle tissue that can affect the kidneys.
“Those patients who refuse to walk and have very tender muscles with severe pain should be seen in the ED,” Dr. Bakir says. “Because we must differentiate those acute conditions from the more severe muscle involvement. This is rarely seen with influenza and other viral infections. We call it rhabdomyolysis.”
Dr. Bakir notes that kidney failure can occur in extreme cases and must be treated in the hospital.
“Because of the breakdown of muscle cells, the kidney canals may become blocked,” Dr. Bakir says.
Rising flu cases and prevention concerns
Dr. Bakir also points to a noticeable increase in influenza cases among children since the COVID-19 pandemic ended.
“Children under five years of age are more likely to have influenza compared to the other ages,” Dr. Bakir says. “There is a significant increase in childhood influenza since the end of the COVID-19 era.”
Low vaccination rates remain a major concern.
“Why can't we decrease the flu numbers? Because, especially in Illinois, the reported coverage of the influenza vaccine is only 24.4%. This is not optimal and sufficient to predict epidemics and complications in this community,” Dr. Bakir says.
Bottom line
Dr. Bakir emphasizes the importance of recognizing warning signs – such as severe pain or refusal to walk – that may signal the need for emergency care. As flu activity continues to rise, prevention efforts, including vaccination and early medical evaluation, remain key to reducing complications in children.