What you need to know about human metapneumovirus cases in China

In recent weeks, scenes of hospitals in China being invaded by masked people have circulated on social media, raising fears of another pandemic.

Beijing has since acknowledged an increase in influenza-like human metapneumovirus (HMPV) cases, especially among children, and attributed it to a seasonal increase.

But HMPV is not like Covid-19, public health experts said, noting that the virus has been around for decades and that almost all children are infected before they turn five.

However, in some very young children and people with weakened immune systems, it can cause more serious illness. 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, in 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 youngest children, including children under two years old, are the 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 diseases doctor in Singapore.

If infected, a “small but significant proportion” among immunocompromised people will develop a more severe disease in which the lungs are affected, with wheezing, difficulty breathing and symptoms of croup.

“Many will need hospital care and a smaller proportion will be 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 viruses survive better in the cold and spread more easily from person to person as people stay indoors more often.

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

In fact, many countries in the northern hemisphere, including China among others, are experiencing a higher 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 the winter,” he said.

Data from health authorities in the US and UK show that these countries have also seen an increase in HMPV cases since October last year.

Experts said fears of a Covid-19-style pandemic are overblown, noting that pandemics are often caused by new pathogens, which is not the case with HMPV.

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

“Almost all children will have at least one HMPV infection by the time they turn five, and we can expect to have multiple reinfections throughout life,” says Paul Hunter, a professor of medicine at the University of East Anglia in England.

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

Still, Dr. Hsu recommends standard general precautions, such as wearing a mask in crowded places, avoiding crowds whenever possible if one is at higher risk for more severe illness from respiratory virus infections, practicing good hygiene of hands and get vaccinated against the flu.