Are there HMPV cases in the U.S.? What we know about human metapneumovirus as infection cases increase in China

As of January 2025, in both the U.S. and China, an increasing concern has developed over human metapneumovirus (HMPV). Notable upticks in reports have been detected. The U.S. has seen increased cases of HMPV beginning in November of 2024. The Centers for Disease Control and Prevention (CDC) reported that at the end of December, there was a two-fold increase, to 1.94%, in tests that came up positive for the virus in given weeks.

In the last week of December, it confirmed almost 300 cases from over 13,800 tests conducted. Experts explain this upsurge to follow the pattern that characterizes most of the seasons' usual spike of the winter respiratory viruses.

According to Dr. Andrew Catchpole, chief scientific officer at hVIVO, although HMPV is usually reported during winter seasons, the serious infection rates in the current wave seem to be higher than historical records.

Symptoms of HMPV include cold-like symptoms, such as cough, fever, nasal congestion, and fatigue. More susceptible populations—especially young children, older adults, and immunocompromised persons—are at increased risk for severe illness from this virus.

The CDC is tracking the situation in China, where cases of HMPV have significantly risen. The rise of U.S. cases does not give health officials reason to raise any alarms as of yet.

According to CBS News, Dr. Carla Garcia Carreno from the Children's Medical Center Plano said:

"This has been circulating for a while, so people have some immunity."

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Increasing HMPV cases in China

Reports indicate that infections have markedly increased, mainly among children, in several major cities, such as Beijing and Guangdong Province.

Health officials have confirmed that HMPV cases have increased among young people, especially in northern China. This has resulted in more hospital visits and emergency room congestion, similar to previous waves of COVID-19.

The World Health Organization (WHO) noted the rise in acute respiratory infections in China but said the overall scale and intensity of respiratory diseases this year are lower than last year.

Meanwhile, India has reported cases and is also increasing surveillance efforts for HMPV.

Concerns in the medical field state that HMPV is not to be confused with COVID-19 because it is already present in human beings and most of them have developed immunity to it. The increased infection rate observed in recent weeks falls within the peak that epidemiologists expected every year and does not signify a new public health disruption of higher severity.

Vanderbilt University's Dr. William Schaffner added that though HMPV causes serious illness in at-risk groups, most cases are mild and self-limiting. Schaffner told ABC News:

“This is that winter respiratory virus season, indeed. So, all of these respiratory viruses -- influenza, COVID, RSV, human metapneumovirus -- they all increase this time of the year, in part because we get so close to each other.”

"We spend time indoors and, of course, all of this holiday traveling, family get-together, and parties have been opportunities for us to get close together and for the virus to be transmitted."

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What is HMPV?

HMPV is a respiratory virus linked to respiratory illnesses in children, the elderly, and other individuals with compromised immune systems.

HMPV was initially identified in the year 2001 by researchers in the Netherlands. This is a negative-sense single-stranded RNA virus in the Pneumoviridae family, which comprises respiratory syncytial virus (RSV) and parainfluenza viruses.

The primary mode by which HMPV spreads is from respiratory droplets produced when an infected individual coughs or sneezes. It can also be transmitted through physical contact with things that have come into contact with the virus. Symptoms of the virus develop from three to five days after contracting the virus.

The severely affected patients present mild flu-like symptoms, which include cough, runny or blocked nose, sore throat, and fever.

In some situations, specifically for infants and other patients with other illnesses, this virus causes problems in the lungs, such as pneumonia and wheezing, and for asthmatic or COPD patients.