hMPV is common virus that causes cold-like symptoms indistinguishable from other common-cold causing viruses and is not usually serious. This means most infections go undiagnosed as people with colds don’t usually have tests to identify the specific bug that’s causing the symptoms.

But it can be serious in the elderly, the immunocompromised, and children.  Cases requiring hospital treatment are almost exclusively in these groups.

No. It was first identified almost a quarter of a century ago by Dutch scientists. hPMV is a common respiratory infection that peaks in winter.  Almost every child will have at least one infection with hMPV by their fifth birthday and we all have multiple reinfections throughout our lifetime.

One of the issues with infections like this is that they are being diagnosed more frequently due to molecular diagnostic tests, so it’s not always easy to know whether there has been an actual increase or just more/better testing.

There has been a surge in infections but these coincided with high rates of influenza and COVID, putting health systems under considerable strain just as they are in many other countries at present – including the UK.  hMPV is usually detected in the winter, but it does seem that the rates of serious infection may be higher in China than in a normal year.

What’s not clear is that just how high the numbers are in China, or if there are issues are arising purely due to it coinciding with high flu and COVID levels. Also China does not have a primary care system (such as GPs in the UK) – if you are sick you present at the hospital so we need to treat headlines about ‘increased hospitalisations’ carefully.

Whilst hMPV – like all viruses – does mutate and change over time with new strains emerging, it is not a virus that is considered to have pandemic potential.  This is because the changes in hMPV are gradual and based on previously circulating strains.

Pandemics occur when a totally new virus enters the human population (such as SARS-CoV-2). Also there is no known animal reservoir for hMPV so it’s not like flu where an entirely new variant can suddenly arise when strains reassort in another animal.

Even if the hMPV in China is a new variant it is likely to be closely related to previously circulating hMPV strains, so there will be a level of pre-existing immunity from previous exposure to hMPV. This will significantly reduce the disease burden in healthy people.

Young people have less developed immune systems, and in the elderly the immune system’s effectiveness declines over time, hence the increased susceptibility to more serious outcomes from infectious diseases.