CA Hit Hard With Little-Known Respiratory Virus

SACRAMENTO, CA — A lesser-known respiratory virus is raising public health concerns across the United States and especially in California, where it is showing up in high concentrations in wastewater samples.

According to Stanford University's WastewaterSCAN, new data shows the spread of human metapneumovirus (HMPV) in high concentrations throughout the Inland Empire and in Northern California, including Sacramento, San Francisco, Santa Rosa, Davis, Napa, Marin, Vallejo, and Novato.

In Southern California, the virus has been detected in low-to-high concentrations. In the Los Angeles metro area, including Santa Monica, Burbank, Northridge, and Simi Valley, the rates of HMPV have been low. In east Los Angeles metro cities such as Long Beach, Torrance, El Monte, and West Covina, the virus has been detected at medium levels. However, San Bernardino County has experienced high levels of HMPV concentrations, including Chino, Ontario, Fontana, Rancho Cucamonga, and Upland.

WastewaterSCAN analyzes wastewater samples from sewage treatment plants to detect infectious diseases and inform public health responses at the local, regional, and national levels.

According to the Centers for Disease Control and Prevention, HMPV is a respiratory illness that usually spreads through winter and spring seasons. The virus can spread through contact with contaminated surfaces, person-to-person contact, and in the air.

Dr. Monica Gandhi, an infectious disease expert at University of California, San Francisco, said late fall and winter are always the seasons for respiratory pathogens, mainly because viruses thrive in cold conditions, and because of people gathering indoors without ventilation.

"This season, unlike the past four winters, we did not have high rates of COVID-19, allowing other viruses to flourish. A high COVID-19 season — or influenza season — can lead to broad immunity for a short period of time, a phenomenon called 'viral interference,' where viruses which cause the common cold cannot compete. However, this season, given the lower rates of COVID-19, we had high rates of influenza in the early winter and are now seeing a virus which causes cold-like symptoms, HMPV," said Dr. Gandhi.

HMPV symptoms include cough, fever, nasal congestion, and shortness of breath. Infected people can spread the virus for up to a week after symptoms first appear, according to the Mayo Clinic.

The virus can also lead to severe but less-common conditions, such as Asthma attacks, middle ear infections, and bronchiolitis — infection in the small airways. It also can trigger croup, the "barking" cough.

The CDC says HMPV virus can also lead to mild illness in healthy children. The first human case of the HMPV was confirmed in 2001 in Holland, according to the Mayo Clinic. It has since spread all over the globe.

The Midwest and Northeast have experienced the highest concentrations of the virus. HMPV is an RNA virus, which like COVID-19, spreads fastest in cold environments, especially among crowds of people who are indoors.

Anyone can be infected with HMPV, but infants, seniors, and people living with immune disorders or chronic obstructive pulmonary disease (COPD) and asthma are at higher risk for severe illness.

Currently, there is no vaccine or treatment available that can prevent HMPV infection.

To prevent the spread of HMPV, the CDC advises people to practice good hygiene, use proper handwashing techniques, cover the mouth and nose when coughing or sneezing, and regularly clean frequently touched surfaces, such as countertops, handrails, and doorknobs.