There’s a good chance you’ve seen headlines about HMPV recently, with some touting “what you need to know” about the virus, aka human metapneumovirus. The answer is: not much.
It’s a common, usually mild respiratory virus that circulates every year, blending into the throng of other seasonal respiratory illnesses that are often indistinguishable from one another. (The pack includes influenza virus, respiratory syncytial virus (RSV), adenovirus, parainfluenza virus, common human coronaviruses, bocavirus, rhinovirus, enteroviruses, and Mycoplasma pneumoniae, among others.) HMPV is in the same family of viruses as RSV.
As one viral disease epidemiologist at the US Centers for Disease Control summarized in 2016, it’s usually “clinically indistinguishable” from other bog-standard respiratory illnesses, like seasonal flu, that cause cough, fever, and nasal congestion. For most, the infection is crummy but not worth a visit to a doctor. As such, testing for it is limited. But, like other common respiratory infections, it can be dangerous for children under age 5, older adults, and those with compromised immune systems. It was first identified in 2001, but it has likely been circulating since at least 1958.
The situation in China
The explosion of interest in HMPV comes after reports of a spike of HMPV infections in China, which allegedly led to hordes of masked patients filling hospitals. But none of that appears to be accurate. While HMPV infections have risen, the increase is not unusual for the respiratory illness season. Further, HMPV is not the leading cause of respiratory illnesses in China right now; the leading cause is seasonal flu. And the surge in seasonal flu is also within the usual levels seen at this time of year in China.
Last week, the Chinese Center for Disease Control and Prevention released its sentinel respiratory illness surveillance data collected in the last week of December. It included the test results of respiratory samples taken from outpatients. Of those, 30 percent were positive for flu (the largest share), a jump of about 6 percent from the previous week (the largest jump). Only 6 percent were positive for HMPV, which was about the same detection rate as in the previous week (there was a 0.1 percent increase).
