Viral myositis is muscle inflammation that occurs as a complication of a systemic viral infection. The muscle inflammation itself is not transmissible from person to person. However, the virus that triggers the condition is highly contagious, meaning a person can catch the virus, but only some individuals will develop myositis.
Defining Viral Myositis
Viral myositis is a secondary condition where skeletal muscle tissue becomes inflamed, typically as the body recovers from a common infection. This inflammation causes pain and weakness (myalgia) and is most often a benign, self-limited process. It commonly manifests as Benign Acute Childhood Myositis (BACM), predominantly affecting school-aged children.
The condition usually develops several days after initial viral symptoms, such as fever, have begun to subside. The influenza virus, particularly type B, is the most frequently reported cause of acute viral myositis. Other common culprits include coxsackieviruses, adenoviruses, and parainfluenza viruses, all common respiratory pathogens. The inflammation may result from the virus directly invading the muscle tissue or, more commonly, from the immune system’s inflammatory response.
Understanding Contagion and Transmission Routes
The muscle inflammation itself is an internal reaction and cannot be spread. The risk of transmission lies entirely with the underlying virus that caused the initial illness. A person with viral myositis may still be shedding the active virus.
The transmission method depends on the causative virus. Influenza and adenoviruses, frequent triggers, are primarily spread through respiratory droplets released when an infected person coughs or sneezes. These droplets can be inhaled or transferred from contaminated surfaces to the mouth, nose, or eyes. Other agents, like coxsackieviruses, are enteroviruses that typically spread through the fecal-oral route, often via contaminated food or water.
Preventing the spread involves standard infection control practices. Consistent handwashing remains the most effective action to disrupt both respiratory and fecal-oral transmission. Annual influenza vaccination reduces the risk of infection by the most common viral trigger. Regularly cleaning high-touch surfaces and avoiding close contact while experiencing viral symptoms also helps contain the pathogen.
Managing Symptoms and Recovery
The clinical presentation often includes sudden-onset pain in the lower extremities, frequently affecting both calf muscles symmetrically. This pain can be severe enough to cause a child to refuse to walk or walk with a characteristic tiptoe gait. These muscle symptoms typically appear after the initial fever and upper respiratory symptoms have begun to resolve.
Viral myositis is generally a self-limiting condition with an excellent prognosis, meaning it resolves on its own without specific medication. The typical course of muscle pain and difficulty walking is short, usually resolving completely within 3 to 10 days. Supportive care is the mainstay of management, focusing on pain relief and maintaining adequate hydration.
Rest is important, and over-the-counter pain relievers, such as ibuprofen or acetaminophen, help manage muscle discomfort. Maintaining fluid intake is particularly important due to the rare but serious complication of rhabdomyolysis, which involves the breakdown of muscle fibers. Dark, reddish-brown urine or a sudden increase in muscle weakness are “red flags” requiring immediate medical attention, as they signal potential kidney injury.