With all eyes on influenza and respiratory syncytial virus, or RSV, this winter and spring, many Americans may have overlooked a common but dangerous respiratory pathogen: human metapneumovirus. HMPV, or hMPV, is a negative-sense single-stranded RNA virus in the Pneumoviridae family and is closely related to avian metapneumovirus subgroup C.

Like RSV, hMPV typically causes symptoms of an upper respiratory infection in healthy adults and children. These usually include a runny nose or nasal congestion, a sore throat and a cough, but can sometimes lead to wheezing, difficulty breathing, pneumonia, and aggravating asthma in some people. It is most active in late winter and early spring, but has also been seen during summer in long-term care facility residents and staff.

Symptoms of a hMPV infection last about two to five days and often go away on their own in healthy people. But young children, older adults and people with weakened immune systems are at higher risk of developing complications from the virus — including secondary infections such as bronchiolitis or pneumonia — and may need to be hospitalized.

Most kids get hMPV by the time they’re three and are likely to have had several infections by the age of five. Kids can spread hMPV by sneezing and coughing, which spray droplets containing the virus onto hands and surfaces. They can also pass it to other kids through close contact. Health care providers don’t treat hMPV in healthy people, but they can help with supportive care and by cleaning contaminated surfaces. In very severe cases, a healthcare provider might use a bronchoscopy — inserting a thin tube with a camera down the throat and into the lung to take a fluid sample.