The Virus You’ve Never Heard Of: China’s HMPV Surge and the U.S. Response

U.S. health authorities confirmed the country’s first severe avian influenza (AI) case.

There has been a reported surge in infections from the lesser-known human metapneumovirus (HMPV) in China. On Wednesday, China’s Centers for Disease Control and Prevention announced a nationwide increase in acute respiratory infections, noting a spike in HMPV cases, particularly in northern regions. The virus has notably affected children and teens under 14.

In a phone interview with a reporter, Professor Eom Joong Sik from the Department of Infectious Diseases at Gachon University Gil Medical Center explained, “HMPV is a known cause of acute respiratory infection. It typically affects children more than adults, usually causing mild to moderate illness. Severe cases requiring hospitalization are rare.” However, he cautions that a mutation in China could change the situation. “If HMPV mutates to attack the lower respiratory tract more aggressively, it could potentially cause more severe pneumonia and bronchitis, possibly leading to life-threatening complications similar to COVID-19.”

He said, “We need more data from Chinese health officials to determine if this surge is solely due to HMPV, a combination with influenza, or seasonal patterns.” He added, “A significant HMPV surge could indicate a more transmissible mutation.”

Recent data from the Korea Disease Control and Prevention Agency show that 88.3% of patients with acute respiratory diseases tested positive for a virus. Over three weeks, HMPV detections increased from 3.2% to 5.3%.

Meanwhile, the U.S. is grappling with its own avian flu concerns. On December 18, 2024, the CDC reported a critical case of H5N1 virus infection in Louisiana, marking the first severe case requiring hospitalization in the country. Since last April, 61 H5N1 cases have been reported nationwide, with over half occurring in California. Most infections were among dairy farm workers exposed to infected poultry. In response, California Governor Gavin Newsom has declared a state of emergency.