New Virus Surges in Northern California

Though only identified in 2001 by Dutch virologists, human metapneumovirus (HMPV) is not a new pathogen. Serological studies show it has been circulating in humans for at least 50 years, and by age five, almost all children have been exposed to the virus. HMPV is part of the Pneumoviridae family, a close relative of the more commonly known respiratory syncytial virus (RSV). It is the second most common cause of lower respiratory infections in young children, after RSV. Symptoms are similar and can include fever, congestion, and a severe cough that can lead to bronchiolitis or pneumonia. The current surge is being monitored through wastewater surveillance, which provides early warnings of disease spread. Elevated levels of HMPV have been detected in several Northern California communities, including Marin, Napa, Novato, Sacramento, and San Francisco. While most people experience mild, cold-like symptoms, HMPV can be severe for young children, older adults, and individuals with weakened immune systems. The peak age for hospitalization in infants with HMPV is between 6 and 12 months. There is currently no vaccine or specific antiviral treatment for HMPV. Medical care is supportive, focusing on managing symptoms, such as using over-the-counter medications for fever and ensuring the patient stays hydrated. HMPV typically circulates in the winter and spring, similar to other respiratory viruses. The virus spreads through respiratory droplets from coughing and sneezing, close personal contact, or touching contaminated surfaces. Health officials recommend preventative measures similar to those for other respiratory illnesses: frequent hand washing, covering coughs and sneezes, cleaning surfaces, and staying home when sick.