What to know about cases of human metapneumovirus in China

In recent weeks, scenes of Chinese hospitals full of masked people have made the rounds on social media, sparking concerns of a new pandemic.

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

But HMPV is not like Covid-19, public health experts said, pointing out that the virus has been around for decades and almost all children are infected before their fifth birthday.

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 causes a mild upper respiratory infection in most people – virtually indistinguishable from the flu.

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

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

The very young, including children under two years old, are most vulnerable to the virus, as well as those with weakened immune systems, including the elderly and those with advanced cancer, says Hsu Li Yang, a doctor infectious disease specialist in Singapore.

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

“Many will need hospital care, and a smaller proportion are likely to die 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 viruses survive cold weather better and are more easily transmitted from person to person to the other, 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, notably China, are experiencing 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,” she said.

Data from health authorities in the United States and the United Kingdom show that these countries are also experiencing an increase in HMPV cases since October last year.

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

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

“Almost all children will have at least one HMPV infection before their fifth birthday and we can expect to have several reinfections throughout our lives,” says Paul Hunter, professor of medicine at the University of East Anglia in England.

“So overall, I don’t think there are any signs right now of a bigger global problem.”

Still, Dr. Hsu advises taking standard general precautions, such as wearing a mask in crowded places, avoiding crowds as much as possible if one is at higher risk of more severe illness from virus infections respiratory tract, practice good hand hygiene and get vaccinated against the flu.