Everything you need to know about the human metapneumovirus hMPV sweeping China

The scenes are eerily familiar – crowded hospitals in China overrun by masked patients seeking medical help as infection tears through the population.

But this time it’s not COVID-19 doing the damage.

Instead, doctors are struggling to cope with high rates of sickness caused by a different organism known as human metapneumovirus or hMPV.

The virus causes cold and flu-like symptoms but can be dangerous to certain groups, particularly children and the elderly.

And, worryingly, other countries are also reporting a spike in cases – which have doubled in the UK in just a month.

So how concerned should you be – and could this be the start of the next pandemic?

Here’s everything you need to know...

WHAT IS hMPV?

HMPV belongs to the same family of infectious bugs as respiratory syncytial virus (RSV), which is already a common source of the lung infection bronchiolitis during winter – hospitalising around 30,000 children and 18,000 adults in the UK every year.

Respiratory viruses spike in winter because we spend more time indoors and in closer proximity to each other, allowing bugs to spread more easily.

HMPV was first officially identified by a team of Dutch scientists in 2001 but some evidence suggests it’s been circulating for hundreds of years.

You may not have heard of it because it is just one of many viruses (at least 200 at the last count) known to cause cold and flu symptoms every year.

In fact, it’s estimated almost every child in the UK has had at least one hMPV infection by the time they reach their fifth birthday which, in most cases, would have presented as just a bit of a sniffle.

WHY ARE WE ONLY HEARING ABOUT IT NOW?

HMPV has hit the headlines because of a surge in cases in China, especially in children – with social media swamped with images of hospitals being overrun.

While it hasn’t released official data, China says there has been a spike in hMPV cases in the north of the country, while India, Malaysia and Kazakhstan have also announced a surge.

HOW DANGEROUS IS IT?

For most healthy adults it’s unlikely to cause serious problems.

But in very young infants as well as the elderly or anyone with a chronic illness including leukaemia or rheumatoid arthritis, hMPV can lead to worrying complications.

These include pneumonia and bronchiolitis (especially in babies), where the virus causes dangerous inflammation in the small airways.

And, especially in the elderly, acute respiratory infections heighten the risks of heart attacks and strokes.

A 2018 study by University College London suggested viral infections could account for almost one in 30 cardiac-related fatalities in those over 75.

HOW WOULD I KNOW IF I’VE GOT IT?

You wouldn’t – unless you were very ill and were tested for it.

But, as with other viruses, these are caused by the body’s immune system trying to fight it off.

Some people may also experience nausea and vomiting, but in most cases this is very short-lived – symptoms often disappear within two to five days.

You probably wouldn’t be tested for the infection unless it caused complications that meant you ended up in hospital, where doctors might need to clarify what was causing your symptoms.

If so, they might do a rapid antigen test – like the DIY COVID tests used during the pandemic – where a nasal swab is examined for the presence of the hMPV virus.

Or they may use a more sensitive and high-tech PCR test (again, similar to those deployed for COVID) which looks for traces of genetic material from the virus in nasal swabs.

ARE CHINA CASES START OF A PANDEMIC?

Experyts have noted that while hMPV is usually detected in the winter period, the rates of serious infection may be higher in China than might normally be expected.

But according to leading experts, it’s unlikely this outbreak is the start of a pandemic.

HMPV replicates slowly and mutates into new strains at a much slower rate than flu or COVID.

Even if this hMPV outbreak is due to a new strain of the virus – for which there’s no evidence yet – expert consensus is it’s likely to be sufficiently similar to other circulating strains and our body’s defences will already have a degree of immunity to it.

“While hMPV does mutate over time, with new strains emerging, it is not a virus that we consider to have pandemic potential,” says Dr Andrew Catchpole, chief scientific officer at hVIVO, an independent research body based in the UK that helps develop vaccines against infectious diseases.

Compare this virus with COVID19 – this was a completely new pathogen.

The human immune system was ill-equipped to deal with it until vaccines arrived.

Pandemics usually occur in one of two ways.

Either a completely new pathogen gets into the human population, or a new variant of an existing virus, formed by a combination of a human and animal version, forms a powerful new organism.

Could this have happened? Dr Catchpole adds: “There is no such animal reservoir of related viruses for hMPV.”

IS IT GOING TO OVERRUN THE NHS?

According to the UK Health Security Agency, hMPV is currently at what it describes as a “medium” level of activity.

For example, in the week ending December 23, 2024, 4.53 per cent of hospital patients in England who had a PCR for the virus tested positive, up from 2.5 per cent at the beginning of the month and five times the amount testing positive in the summer.

That said, the numbers are not radically different from the same time last year.

To put it in context, the number of people testing positive for flu during the same week was more than 14 per cent, and for RSV 7.35 per cent.

Paul Hunter, a professor in medicine and expert in infectious diseases at the University of East Anglia, said it may be improved testing methods are detecting more cases – rather than infections actually rising dramatically.

HOW DOES IT SPREAD?

In much the same way as other cold, flu or COVID viruses – it’s largely airborne and moves from one person to another through inhaling contaminated droplets.

These travel deep into the lungs, where the virus hijacks healthy cells to use them as a reproduction “factory”, to spread further.

However, just as with cold and flu bugs, hMPV can also be picked up from touching contaminated surfaces or direct contact with an infected person, especially if they touch you in areas where the virus can easily invade the body – such as around the mouth, nose or eyes.

Symptoms show within three to six days.

HOW CAN I AVOID CATCHING IT?

The most effective defence is the same basic hygiene measures for any winter virus: washing hands with soap and warm water (to get rid of any viral particles lurking on your skin) and regularly cleaning surfaces around the home.

Some experts advise steering clear of high-contact surfaces, such as handrails and doorknobs in busy places – and wearing face masks in crowded environments.

HOW DO I TREAT IT?

Most cases don’t need treatment other than the usual over-the-counter remedies for cold and flu symptoms, such as paracetamol and ibuprofen.

IS THERE A VACCINE?

No, but there are several in development targeted at babies.