In the 2019-2020 flu season, nearly 56 million cases of influenza were reported, according to the Centers for Disease Control and Prevention. In many of those cases, the virus was accompanied by muscle and joint aches.
“Muscle pain is never enjoyable, and can cause alarm in patients,” says Thomas Donaldson, MD, chair of orthopaedics at Loma Linda University Health. “They can be especially frustrating for people who already experience issues with joint or bone health,” he says.
When a body is infected with a virus, the immune system works to fight the infection. Donaldson says this fight could lead you to feel muscle inflammation and weakness — called myositis — or joint and muscle pain — called myalgia. Pain manifested in the joints is called arthralgia is also a commonly associated with a fever.
What’s causing the pain?
When infected by a virus, the body mounts an immune response, sending antibodies to seek out attack the virus, blocking it from spreading further. “The pain you feel in your joints when you have the flu is due to the body’s immune response, not the actual flu,” Donaldson says. Once the antibodies have bonded with influenza, the body produces a type of protein to kill the virus. This protein is what causes the symptoms, Donaldson says.
Additionally, white blood cells produce cytokines — which are small proteins used for cell signaling — which causes inflammation in muscles and joints. “Inflammation can cause pain that feels similar to mild arthritis,” Donaldson says.
When should you seek help?
Fortunately, the aches and pains are temporary. Once the body fights the infection, the pain should subside. If symptoms are ongoing or severely worsening, there may be a more significant underlying issue, Donaldson says.
"Influenza cannot be treated with antibiotics, but prolonged viral symptoms can turn into a bacterial bronchitis and or pneumonia," he says. "A cough producing mucas that is not clear or white may require more aggressive treatment involving antibiotics."
While it’s common for joints to feel stiff or sore, Donaldson says you should be able to move them fully. “Even if it’s uncomfortable, you should still have full mobility of your joints,” he says. “If you lose movement or your joints are red or swollen, consider seeking medical attention.”
To learn more about what you can do to protect yourself and your family during the flu season, visit our flu page at lluh.org/flu. Loma Linda University Health Primary Care and Urgent Care locations are available for in-person or virtual visits. Appointments can be made quickly and easily online at MyChart or by calling 909-303-9939.