Human Metapneumovirus (HMPV) Spreading in Northern California, Filling the Gap Left by Quieter COVID Season

As COVID-19 cases remain relatively low this season, another respiratory virus is gaining traction across Northern California. Human metapneumovirus (HMPV), a common cause of respiratory illness, is circulating widely in communities from San Francisco to Sacramento, leading to increased absenteeism in offices and schools.

What is Human Metapneumovirus (HMPV)?

Human metapneumovirus (HMPV) is a virus that typically causes respiratory infections, particularly during the winter and spring months. It was first discovered in 2001 and is closely related to the virus that causes RSV (Respiratory Syncytial Virus). According to the Centers for Disease Control and Prevention (CDC), HMPV can cause mild to severe illness, with symptoms similar to those of a common cold or the flu.

Where is HMPV Currently Spreading?

Recent data from WastewaterSCAN indicates high concentrations of HMPV in several Northern California locations, including:

• San Francisco
• Marin
• Vallejo
• Napa
• Novato
• Santa Rosa
• Sacramento
• Davis

The virus isn’t limited to California, with data showing an upward trend of HMPV throughout the U.S. The Midwest and Northeast are currently experiencing the highest rates, according to WastewaterSCAN data.

Symptoms of HMPV

HMPV typically causes symptoms such as:

• Cough
• Fever
• Congestion
• Runny nose
• Sore throat

In some cases, particularly in young children, HMPV can lead to more severe complications like:

• Bronchiolitis (inflammation of the modest airways in the lungs)
• Croup (characterized by a distinctive “barking” cough)

The Mayo Clinic describes the croup cough as sounding similar to a seal barking, and it is most common in small children.

Why is HMPV Increasing Now?

Dr. Monica Gandhi, an infectious disease specialist at UC San Francisco, explains that the decrease in COVID-19 cases has created an opportunity for other respiratory viruses, like influenza and HMPV, to spread. “These illnesses ‘compete with each other,’” she stated to SFGATE. “When we had big COVID surges, we saw really low rates of other common cold viruses.”

HMPV, being an RNA virus like COVID-19, thrives in colder environments. As people spend more time indoors during the winter months, the virus spreads more easily through close contact, contaminated surfaces, and airborne droplets.

Prevention and Treatment

The CDC recommends the following measures to prevent the spread of HMPV:

• Stay home when sick
• Wash your hands frequently
• Regularly clean surfaces

Currently, there are no specific treatments or vaccines for HMPV. Most people recover with rest, fluids, and supportive care.

Tracking HMPV Through Wastewater Surveillance

Wastewater surveillance is playing an increasingly important role in tracking the spread of infectious diseases, including HMPV. Programs like WastewaterSCAN and the California Department of Public Health (CDPH) Wastewater Surveillance (WWS) monitor wastewater for the presence of various pathogens, providing valuable data to public health officials. California Wastewater Surveillance Center of Excellence and WastewaterSCAN provide dashboards visualizing this data across the United States.