What you need to know about human metapneumovirus cases in China

In recent weeks, scenes of hospitals in China overflowing with people wearing masks have surfaced on social media, raising concerns about the new pandemic.

Since then, Beijing has acknowledged a surge in cases of influenza-like human metapneumovirus (HMPV), particularly among children, and attributed it to a seasonal spike.

But HMPV is not like Covid-19, health experts said, noting that the virus has been around for decades and nearly every child is infected by their fifth birthday.

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

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

First discovered in the Netherlands in 2001, the virus spreads through direct human-to-human contact or when someone touches surfaces infected with it.

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

The youngest children, including children under two years old, are most vulnerable to the virus, as are people with weakened immune systems, including the elderly and cancer patients, said Hsu Lee Yang, an infectious disease doctor in Singapore.

If infected, a “small but significant proportion” of immunocompromised people will develop a more serious illness involving the lungs, with wheezing, shortness of breath and symptoms of croup.

“Many will need inpatient care, a smaller number are 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 that’s because viruses survive better in the cold and are more easily spread from person to person when people stay indoors more.

In northern China, the current surge in HMPV coincides with cold temperatures expected to persist into March.

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

“While this is a concern, the increased prevalence is likely a normal seasonal increase seen in winter,” she said.

Data from health authorities in the US and UK show that these countries have also seen a surge in HPV cases since last October.

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

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

“Almost every child will have at least one HMPV infection before their fifth birthday, and we can expect to have several re-infections over the course of a lifetime,” says Paul Hunter, professor of medicine at the University of East Anglia in England.

“So I don’t think there’s any sign of a bigger global problem right now.”

However, Dr. Hsu recommends standard general precautions such as wearing a mask in public places, avoiding crowds if possible if you are at higher risk of more severe illness from respiratory viral infections, practicing good hand hygiene and getting a flu vaccine.