HMPV in California: Symptoms, Spread & What to Know Now
A respiratory virus, human metapneumovirus (HMPV), is circulating in parts of California, prompting increased monitoring by public health officials. While cases are rising, experts emphasize there is currently no cause for widespread alarm.
Data from the WastewaterScan Dashboard indicate elevated concentrations of HMPV in wastewater across much of Northern California. A Los Angeles Times analysis identified increases in HMPV levels in wastewater samples collected from Merced in the San Joaquin Valley and Novato and Sunnyvale in the San Francisco Bay Area between mid-December and the end of February . HMPV has also been detected in Los Angeles County, though at lower to moderate levels.
HMPV isn’t a new virus; it was first identified in , according to the U.S. Centers for Disease Control and Prevention (CDC). However, its typical seasonal pattern was disrupted by the COVID-19 pandemic. The current resurgence may signal a return to pre-pandemic respiratory disease patterns, as immunity levels have changed.
What is HMPV?
Human metapneumovirus is a common cause of respiratory illness, affecting people of all ages. It spreads through close contact with infected individuals or by touching contaminated surfaces. Like other respiratory viruses, such as influenza, HMPV is more prevalent during colder months, according to infectious disease experts.
Typically, HMPV cases begin appearing in January, peaking in March or April, and declining by June. The pandemic altered this pattern, as reduced social interaction limited exposure and the development of natural immunity.
Prior to , regular seasonal exposure provided a degree of population immunity. This immunity waned during the pandemic, leaving individuals more susceptible when normal activities resumed. Unlike influenza or COVID-19, there is currently no vaccine available to prevent HMPV infection.
National test positivity for HMPV peaked at 11.7% in late March , according to the National Respiratory and Enteric Virus Surveillance System (NREVSS). The peak in was 7.43%. As of February , the most recent date with complete data, the positivity rate was 6.1%.
What are the symptoms of HMPV?
Most individuals experience mild, cold-like symptoms, including cough, fever, nasal congestion, and sore throat. However, HMPV can sometimes lead to more severe illness, particularly in vulnerable populations.
Potential complications include asthma exacerbations, middle ear infections, croup (characterized by a “barking” cough), and, in more severe cases, bronchitis or pneumonia. Individuals with weakened immune systems, young children, and older adults are at higher risk of developing severe disease.
How is HMPV treated?
Currently, there is no specific antiviral treatment or established treatment protocol for HMPV. Medical care focuses on supportive measures to alleviate symptoms. This typically involves rest, increased fluid intake, and over-the-counter medications to manage fever and discomfort.
In some cases, oxygen therapy may be required if a patient experiences difficulty breathing. However, most people recover on their own without requiring hospitalization.
How can you protect yourself from HMPV?
Preventive measures are similar to those recommended for other respiratory viruses. The American Lung Association recommends frequent handwashing with soap and water, or using an alcohol-based hand sanitizer when soap and water are unavailable. Regular cleaning of frequently touched surfaces is also advised.
Improving air circulation by opening windows, avoiding close contact with sick individuals, and avoiding touching the eyes, nose, and mouth can further reduce the risk of infection.
While the rise in HMPV cases is being monitored, public health officials emphasize that the virus is not new and that most infections are mild. Practicing good hygiene and taking preventative measures can help minimize the spread of HMPV and protect vulnerable individuals.