What is HMPV, is it in Ireland, and how worried should we be?

Social media is alive with images of crowded hospitals in China being overrun with masked people. Inevitably, this has been accompanied with disinformation about another looming infectious disease pandemic, some five years since Covid-19 (Sars-CoV-2) took over our lives.

So what is going on and how worried should we be?

According to the Chinese authorities, they are dealing with an outbreak of a bug called human metapneumovirus (HMPV) in the north of the country. First identified in the Netherlands in 2001, the microbe is in the same family as the respiratory syncytial virus (RSV) – the disease which, alongside influenza, is causing such pressure on hospital beds here in Ireland at present.

HMPV is a respiratory disease that causes flu or cold-like symptoms. It has primarily been found in younger children, most of whom readily overcome the infection. But the virus can lead to more serious complications, especially among the elderly, very young children and those who are immunocompromised.

And if you have been struck down with Covid recently, which we know in some people can take the edge off their immune systems, then you may be at risk from a more serious episode of HMPV infection.

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I looked after one patient in their mid-60s last winter who contracted HMPV some two weeks after getting Covid. Despite not having any pre-existing lung disease or problems with their immune system, they needed a week’s hospital treatment to get over the severe wheeze and cough brought on by the infection.

Is HMPV circulating in Ireland?

The Health Protection Surveillance Centre (HPSC) does not report HMPV levels in the Republic. Its Respiratory Virus Notification Data Hub focuses on influenza, RSV and Covid-19 numbers.

However, data from the UK suggests HMPV levels are at expected rates in these islands. The UK Health Security Agency’s (UKHSA) weekly national flu and Covid-19 surveillance report found that overall rates of HMPV have increased slightly to 4.5 per cent. It found the highest positive rate (10 per cent) was among those five years old and younger. The UK Health Security Agency added its surveillance indicates that HMPV levels are consistent with what we typically expect during winter.

How serious is HMPV?

The symptoms of HMPV are similar to a cold or flu, and it is one of several viruses often lumped under a broad definition of the “common cold”, according to Dr Jacqueline Stephens, a senior lecturer in public health at Flinders University in Australia. It is not a notifiable disease like Covid-19 or influenza. HMPV is a single-stranded RNA virus that spreads through respiratory droplets or contact with contaminated surfaces.

How might you know that you have HMPV?

Symptoms include cough, wheeze, fever, nasal congestion, and fatigue, with an incubation period of three to six days. Unlike Covid-19 or influenza, there is no vaccine or specific antiviral treatment for HMPV. So treatment is supportive, including rest, paracetamol and maintaining a good fluid intake.

How worried should we be?

There is no need to be concerned. HMPV is not like Covid-19; it has been around for several decades and there is a level of immunity in the global population from past infections. Covid-19 was a new disease which had never infected humans before, which facilitated its spread to pandemic-levels.

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What can we do if the amount of circulating HMPV increases?

There is certainly no need for the levels of social isolation that were introduced during the Covid pandemic. If you are infected, then it’s best not to go to work. Wash your hands thoroughly and practise good cough and sneeze etiquette. And if you do have to go out into the community consider wearing a face mask so that you don’t pose a risk of serious HMPV infection to vulnerable people.

HMPV is in no way similar to Covid-19. The rise in cases in northern China is nothing more than the usual seasonal increase seen with many viral illnesses.

mhouston@irishtimes.com