What to know about human metapneumovirus cases in China

In recent weeks, scenes of hospitals in China being overrun by masked people have made the rounds on social media, raising concerns about another pandemic.

Beijing has since acknowledged a rise in cases of human influenza-like metapneumovirus (HMPV), particularly among children, and attributed it to a seasonal peak.

But HMPV is not like Covid-19, public health experts said, noting that the virus has been around for decades, with almost all children infected by their fifth birthday.

However, in some very small children and people with weakened immune systems, it can cause more serious illnesses. Here’s what you need to know.

HMPV is a virus that will cause a mild upper respiratory tract infection—virtually indistinguishable from the flu—for most people.

First identified in the Netherlands in 2001, the virus spreads through direct contact between people or when someone touches surfaces contaminated with it.

Symptoms for most people include cough, fever and nasal congestion.

The very young, including children under the age of two, are most vulnerable to the virus, along with those with weakened immune systems, including the elderly and those with advanced cancer, says Hsu Li Yang, an infectious disease doctor at Singapore.

If infected, a “small but significant proportion” among the immunocompromised will develop a more severe disease where the lungs are affected, with wheezing, shortness of breath and symptoms of croup.

“Many will require hospital care, with a smaller proportion at risk of dying from the infection,” Dr Hsu said.

Like many respiratory infections, HMPV is most active in late winter and spring – some experts say this is because the virus survives better in the cold and is more easily passed from one person to another, since people stay at home more often.

In northern China, the current HMPV spike coincides with low temperatures that are expected to last until March.

In fact, many countries in the northern hemisphere, including but not limited to China, are experiencing an increased prevalence of HMPV, said Jacqueline Stephens, an epidemiologist at Flinders University in Australia.

“While this is concerning, the increase in prevalence is likely the normal seasonal increase seen in winter,” he said.

Data from the health authorities in the United States and the United Kingdom show that these countries, too, have had a peak in cases of HMPV since October of last year.

Fears of a Covid-19-style pandemic are overblown, experts said, noting that pandemics are typically caused by new pathogens, which is not the case for HMPV.

HMPV is present worldwide and has been for decades. This means that people around the world have “some degree of existing immunity due to previous exposure,” Dr. Hsu said.

“Almost every child will have at least one infection with HMPV by their fifth birthday and we can expect to have many reinfections throughout life,” says Paul Hunter, professor of medicine at the University of East Anglia in England.

“So overall, I don’t think there is currently any sign of a more serious global problem.”

However, Dr. Hsu advises standard general precautions such as wearing a mask in crowded places, avoiding crowds where possible if one is at greater risk of more severe illness from respiratory virus infections, practicing good hand hygiene, and getting the flu vaccine.