"Quiet" COVID Season Fuels Rise of Respiratory Virus HMPV in Northern California

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NORTHERN CALIFORNIA — March 4, 2026 — As spring approaches, a less-familiar respiratory pathogen is making its presence felt across Northern California. Offices and schools from San Francisco to Sacramento are reporting a noticeable uptick in absenteeism, driven not by COVID-19 or the flu, but by Human Metapneumovirus (HMPV).

Recent data from WastewaterSCAN, a national network monitoring infectious diseases in municipal sewage, has detected elevated concentrations of HMPV in several key regions, including Marin, Vallejo, Napa, Novato, Santa Rosa, and Davis. While typically a seasonal visitor, the current surge is drawing attention from health officials as it fills the gap left by a relatively mild winter for other major respiratory viruses.

A “Competitive” Viral Landscape

The rise of HMPV this season may be a direct result of the shifting dynamics of viral circulation. Dr. Monica Gandhi, an infectious disease specialist at UC San Francisco (UCSF), notes that respiratory viruses often “compete” for hosts.

“These illnesses compete with each other,” Dr. Gandhi explained. “During the years of major COVID-19 surges, we saw record-low rates of other common respiratory viruses. Now that COVID-19 activity is ‘quieter’ this season, viruses like influenza and HMPV are getting their chance to circulate more freely.”

While California’s milder weather and better ventilation often curb the rapid indoor spread seen in the Midwest and Northeast—where HMPV levels are currently highest—the localized spikes in Northern California signal a significant community spread.

Symptoms and the “Barking” Cough

HMPV generally presents as a standard upper respiratory infection. For most healthy adults, symptoms are indistinguishable from the common cold, including:

- Congestion and runny nose
- Persistent cough
- Sore throat
- Fever

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However, in pediatric cases, HMPV can take a more distinctive turn. Health providers are warning parents to listen for a “barking” cough, a hallmark of croup, which HMPV can trigger in young children. The virus is also a leading cause of bronchiolitis—inflammation of the small airways in the lungs—which can cause wheezing and labored breathing in infants.

Vulnerable Populations at Risk

While the majority of people recover with rest and hydration, HMPV is not benign for everyone. According to the Centers for Disease Control and Prevention (CDC), HMPV is responsible for approximately 10% to 12% of all respiratory illnesses in children.

Vulnerable groups include:

Children under age 5: Particularly those born prematurely or with low birth weights.
Adults over 65: The aging immune system is less effective at clearing lower respiratory infections, which can lead to viral pneumonia.
Immunocompromised individuals: Those with underlying conditions like asthma, COPD, or weakened immune systems are at a higher risk for severe complications.

The Diagnostic Challenge

One of the primary hurdles in managing HMPV is that it is rarely included in routine “rapid tests” found in drugstores.

“One of the biggest reasons people—and even some physicians—aren’t as aware of HMPV is that it isn’t always part of the standard respiratory panel,” says researchers in recent clinical reviews. Because symptoms overlap significantly with RSV and the flu, healthcare providers often rely on comprehensive PCR panels to confirm the virus, a step usually reserved for more severe cases.

No Vaccine, No Cure: The Path to Recovery

Unlike COVID-19 or the flu, there is currently no vaccine and no specific antiviral treatment for HMPV. Management is strictly supportive, focusing on:

Hydration: Maintaining fluid intake to thin mucus.
Rest: Allowing the body to focus its energy on the immune response.
Fever Management: Using over-the-counter medications like acetaminophen or ibuprofen as directed by a professional.

Prevention remains the most effective tool. The CDC and local health departments continue to emphasize the “back to basics” approach: frequent handwashing for at least 20 seconds, staying home when symptomatic, and regular disinfection of high-touch surfaces like doorknobs and phones.

Looking Ahead

While the current uptick in Northern California is significant, health experts do not believe it warrants a return to pandemic-era restrictions. Instead, it serves as a reminder that the post-pandemic “normal” includes a diverse ecosystem of seasonal viruses that require ongoing vigilance.

“We need to monitor these trends, especially for our most vulnerable neighbors,” Dr. Gandhi noted. “But for the general population, the playbook remains the same: stay home if you’re sick and keep your hands clean.”

Medical Disclaimer: This article is for informational purposes only and should not be considered medical advice. Always consult with qualified healthcare professionals before making any health-related decisions or changes to your treatment plan. The information presented here is based on current research and expert opinions, which may evolve as new evidence emerges.