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Sewage surveillance is flagging a notable surge of human metapneumovirus across parts of Northern California, with samples from San Francisco and several surrounding communities showing elevated levels. The pattern—which climbed sharply in January and remains above typical background levels into early March—matters because the virus can cause serious respiratory illness in vulnerable people and adds pressure to health systems already managing seasonal infections.
What the wastewater data show
Public health monitoring programs that test wastewater for respiratory pathogens have picked up increased signals of HMPV in multiple Bay Area locations, including San Francisco, Marin, Vallejo, Napa, Novato, Santa Rosa, Sacramento and Davis. Similar upticks are appearing in parts of the Midwest and the Northeast, indicating the current wave is not confined to California.
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The national network that coordinates these efforts—the CDC’s National Wastewater Surveillance System (NWSS) and local wastewater scanning initiatives—uses sewage samples to detect trends at the community level before many cases are reported clinically.
Why this matters now
Unlike influenza and COVID-19, HMPV remains less familiar to many clinicians and the public, which can delay recognition during seasonal surges. For hospitals and outpatient clinics, an increase in HMPV adds to caseloads of cough and shortness of breath and can worsen outcomes for people with chronic lung disease.
Symptoms, risks and complications
In otherwise healthy adults and children, infection typically causes cough, fever and nasal congestion. But for certain groups the stakes are higher: infants and toddlers, older adults, and people with weakened immune systems or chronic respiratory conditions face a greater risk of severe disease.
Complications can include bronchiolitis, pneumonia, asthma exacerbations, croup and other lower-respiratory infections. People with chronic obstructive pulmonary disease (COPD) or similar conditions may experience meaningful worsening of baseline symptoms.
How it spreads and when to expect it
HMPV transmits through close contact—via respiratory droplets from coughing or sneezing and by touching contaminated surfaces. The virus most often causes outbreaks from late fall into spring, which aligns with the current surveillance signal.
Testing, treatment and prevention
There is currently no vaccine and no specific antiviral proven for HMPV; diagnosis is established through laboratory testing ordered by a clinician. Care focuses on symptoms: hydration, rest and medical evaluation when breathing problems, high fever, persistent lethargy or rapid deterioration occur.
- Key places where wastewater levels are elevated: San Francisco, Marin, Vallejo, Napa, Novato, Santa Rosa, Sacramento, Davis.
- Common symptoms: cough, fever, nasal congestion, difficulty breathing.
- Higher-risk groups: young children, older adults, immunocompromised people, those with chronic lung disease.
- Prevention steps: cover coughs and sneezes, wash hands thoroughly, clean frequently touched surfaces, stay home or mask up when sick.
If you are in a high-risk category or caring for someone who is, consult a healthcare provider promptly if symptoms worsen. Public health officials say wastewater monitoring provides an early indicator of rising community transmission, giving clinicians and residents a chance to prepare as the seasonal wave continues to ebb and flow.
