HMPV Virus Outbreak in the USA: Symptoms & Risks

A little-known virus, human metapneumovirus (HMPV), is currently spreading rapidly in the United States. Older adults, young children, and individuals with weakened immune systems are particularly vulnerable. Despite its prevalence, there is currently no vaccine or specific treatment available, raising concerns among health authorities.

A virus previously overshadowed by COVID-19 is now gaining attention in the United States: human metapneumovirus (HMPV). Since the fall of 2025, the virus has been spreading quickly, from the West Coast to the Northeast. According to the latest data from the Centers for Disease Control and Prevention (CDC), HMPV accounted for over five percent of positive respiratory tests in the first week of March, an increase from 3.8 percent in the last week of February. The CDC has been tracking HMPV circulation patterns alongside RSV, noting a return to typical seasonal trends after disruptions during the COVID-19 pandemic.

What is Human Metapneumovirus?

HMPV isn’t a novel virus; it was first identified in 2001 and belongs to the same virus family as respiratory syncytial virus (RSV). The CDC describes HMPV as causing respiratory illness in people of all ages, though it typically results in mild illness in healthy children. Young children, older adults, and people with compromised immune systems are at higher risk for more severe illness. In children, the virus can lead to bronchiolitis, an infection of the lower airways that often requires hospitalization. Symptoms commonly include cough, fever, nasal congestion, and shortness of breath, which can sometimes progress to bronchitis or pneumonia.

While HMPV isn’t considered exotic, it poses a risk to specific groups. Particular caution is advised in settings like nursing homes or shelters, where respiratory viruses can spread easily. Symptoms are similar to those of a severe cold or the flu, including cough, fever, and difficulty breathing. The mortality rate is comparable to that of influenza and RSV, but significantly higher in individuals with weakened immune systems.

Limited Treatment Options and Prevention

Currently, there is no specific antiviral treatment or vaccine for HMPV. Cleveland Clinic notes that treatment focuses on supportive care, managing symptoms as they appear. Health experts recommend basic preventative measures such as regular handwashing, disinfecting surfaces, and wearing masks around vulnerable individuals. If severe symptoms like difficulty breathing or chest pain develop, prompt medical attention is crucial.

Most people can recover at home with rest and fluids. However, it’s important to be aware of potential complications, especially in high-risk groups. These can include asthma attacks, ear infections, and, in severe cases, pneumonia. The CDC emphasizes that HMPV infections are most common during winter through spring, but can occur year-round.

Understanding HMPV Seasonality and Co-Circulation

The timing of HMPV outbreaks often overlaps with RSV season, typically running from winter through spring. However, recent data suggests some shifts in these patterns. A CDC report from April 2025 highlighted that RSV season has been occurring earlier than usual in recent years, and HMPV circulation is returning to its typical spring peak after a significant decline during the initial phases of the COVID-19 pandemic. This co-circulation of both viruses presents challenges for healthcare systems and underscores the importance of accurate diagnostic testing.

Diagnostic Testing and Public Health Surveillance

While there isn’t a routine test for HMPV, healthcare providers can test for it using molecular diagnostic methods. However, the CDC notes that testing isn’t always performed, and there is no specific treatment to guide clinical decisions. Increased awareness and broader apply of these diagnostic tests have contributed to a better understanding of HMPV’s impact as a cause of respiratory infections.

Public health surveillance plays a crucial role in monitoring HMPV circulation and identifying potential outbreaks. The CDC and state health departments collect data on HMPV cases to track trends and inform public health recommendations. Understanding these circulation patterns can help guide the timing and prioritization of testing, facilitate prompt outbreak detection, and ensure healthcare systems are prepared for seasonal increases in respiratory illnesses.

What to Expect Moving Forward

The ongoing circulation of HMPV highlights the continued importance of respiratory hygiene and preventative measures, particularly for vulnerable populations. While research into potential vaccines and antiviral treatments is ongoing, the current focus remains on supportive care and preventing the spread of the virus. Health authorities will continue to monitor HMPV activity and update guidance as needed. Individuals experiencing respiratory symptoms should consult with a healthcare professional for appropriate evaluation and management. Staying informed about official public health updates from the CDC and local health departments is also recommended.