Viral myositis: Symptoms, treatments, and more
Myositis is a group of conditions that cause muscle inflammation and weakness. Viral myositis occurs as a complication of a viral infection, such as influenza viruses or enteroviruses.
Viral myositis, more commonly known as benign acute childhood myositis (BACM), is a complication of a viral infection that can cause muscle weakness and difficulty moving.
Treatment may involve antiviral medications to address the underlying infection if one is still present. Doctors may also need to monitor the affected person and administer fluids to prevent dehydration.
Infective myositis, which includes viral myositis, is most common in children. The mean age of onset for BACM is 6.8 years, according to a 2024 review of 22 studies.
Although less common, viral myositis can also occur in adults. For example, a 2021 case report highlights myositis symptoms in a 38-year-old adult following the flu.
A 2025 study suggests that BACM is a rare condition that is more likely to occur during winter.
A 2024 review suggests that influenza B is most commonly associated with BACM. Influenza A was the second most likely virus. Other viruses in the review’s research included:
Myositis can also
Since BACM tends to occur after a viral infection, an affected person may also have recently had symptoms of a viral infection, such as the flu.
During a diagnosis, a doctor may also find that a person has high levels of an enzyme called creatine phosphokinase (CPK).
In rare cases, people may develop complications, such as rhabdomyolysis. Rhabdomyolysis is a condition in which the muscles start to break down. This complication requires urgent medical attention.
A 2024 case series suggests that BACM tends to be a self-limiting disease. This means it usually gets better on its own and does not need treatment.
A 2024 case report describes the treatment of viral myositis in a four-year-old using supportive measures and oseltamivir (Tamiflu). Oseltamivir is a type of antiviral medication.
However, the same case report highlights the limited efficacy of antivirals for treating BACM. More research is necessary to understand how effective antivirals may be at treating BACM.
For someone with viral myositis, a doctor may instead focus on pain relief, keeping the person hydrated, and monitoring their symptoms to quickly diagnose and treat any complications, such as rhabdomyolysis.
A 2024 case series highlights that the influenza vaccine can help prevent flu complications. However, the researchers state that more research is necessary to prove whether a flu vaccine can help prevent BACM.
Viral myositis tends to occur following a viral infection. People can reduce their likelihood of getting a viral infection, which may help prevent BACM.
If a person develops muscle pain or difficulty walking following a viral infection, it can be beneficial to speak with a healthcare professional for a diagnosis.
Similarly, if a parent or caregiver notices a child with reluctance or difficulty walking and signs of lower limb pain after a viral infection, they should speak with a healthcare professional.
A prompt diagnosis can help a person get treatment for symptoms that affect their daily life, such as pain. It can also help to rule out viral myositis if there is another underlying cause for a person’s symptoms.
Viral myositis, also known as benign acute childhood myositis (BACM), is a condition that occurs following a viral infection. People develop muscle inflammation, which can cause leg pain and difficulty walking.
BACM most often affects children, but it can affect adults, too. The most commonly associated viral infection is influenza B.
Viral myositis tends to get better on its own. However, a doctor may recommend treatments to manage a person’s symptoms and monitor them in case of complications.