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Scientists comment on cases of Human Metapneumovirus (hMPV) reported in China.
Prof Antonia Ho, Professor and Hononary Consultant of Infectious Diseases, Medical Research Council-University of Glasgow Centre for Virus Research, said:
“Human metapneumovirus (hMPV) is a respiratory virus that predominantly causes mild flu-like illness, though can cause severe disease, such as bronchiolitis and pneumonia, in those at extremes of age and also those with a compromised immune system, such as individuals who have had an organ or stem cell transplant or individuals with HIV infection. Infection is more common in children than adults; serology studies suggest that most children have been infected by the age of 5.
“hMPV was first identified by Dutch resesarchers in 2001 in archived children’s respiratory samples in whom no bugs have been isolated, and has since been found worldwide.
“Seasonality is similar to that of influenza, with peak activity in winter/early spring, therefore high case numbers of hMPV identified in China may not be out of the ordinary.
“hMPV is probably less well studied, compared to other respiratory viruses, such as flu, SARS-CoV-2 than RSV.”
Dr Conall Watson, Consultant Epidemiologist at the UK Health Security Agency, said:
“hMPV is a common respiratory infection in winter, and we typically see activity reaching a peak at this time of year. Infections are usually mild, causing symptoms of a common cold. Our surveillance systems in GP surgeries and hospitals indicate that levels are in line with what we would expect to see. Most people have had hMPV by the time they are five years old and catch it again throughout their lives.
“As with all respiratory viruses, you can help reduce infections being passed on through regular handwashing and catching coughs and sneezes in tissues and throwing them away. If you have symptoms such as a high temperature, cough and feeling tired and achy, try to limit your contact with others, especially those who are vulnerable. There are many viruses in circulation at the moment, including flu – if you have symptoms of a respiratory illness and you need to go out, our advice continues to be that you should consider wearing a face mask.”
Prof Martin Michaelis, Professor of Molecular Medicine, University of Kent, said:
What is the human metapneumovirus (HMPV)?
“The human metapneumovirus (HMPV) was discovered in 2001. It belongs to the large group of viruses that cause common colds and flu-like diseases. Like influenza viruses, coronaviruses (including SARS-CoV-2 that causes Covid-19), and its relative respiratory syncytial virus (RSV), HMPV has an RNA genome (i.e. it stores its genetic information in RNA molecules and not in DNA molecules like all living organisms, including microorganisms, plants, and animals).
What disease(s) are caused by HMPV?
“HMPV is very common. At the age of five, almost everyone has been infected with HMPV. It causes common cold-like diseases with symptoms including a cough, fever, and a runny and/ or congested nose.
“Young children, the elderly, and immunocompromised individuals can develop more severe disease such as bronchitis and pneumonia.
Are there treatments for HMPV, and how can I protect myself?
“No, there are no vaccines or drugs available for HMPV. The only way of protecting yourself is by avoiding infections. HMPV spreads via the air and contaminated surfaces. Thus, protection measures are the same that we know from Covid-19 – they include thorough hand hygiene, avoiding contact with others, and wearing a face mask. Being cautious will protect you and others, in particular vulnerable individuals, who are at an increased risk.
Why is HMPV in the news now?
“Most respiratory viruses, including HMPV, predominantly spread when it gets colder, when they are more stable and we spend more time indoors.
“Even before Covid-19, large outbreaks of respiratory illnesses put hospitals under pressure in the winter. However, we did not care about the viruses that caused them. Today, there is more interest in the causes of respiratory diseases, and this year there is a relative high number of HMPV cases. However, you would be surprised how little we still know about common cold viruses in general.
Will HMPV cause another pandemic?
“This is extremely unlikely. In contrast to SARS-CoV-2, the coronavirus that causes Covid-19, HMPV has been around for decades, and there are high levels of immunity in the population.”
Dr Andrew Catchpole, Chief Scientific Officer, hVIVO, said:
What is hMPV?
“hMPV is relatively common virus that causes cold symptoms. It is a member of the same virus family as RSV. In healthy adults the infection would be expected to cause common cold like symptoms indistinguishable from many other common-cold causing viruses and not normally serious. Hence most infections in the population will go undiagnosed as people with colds do not normally have tests to identify the specific pathogen. It can however, be serious in the elderly, immunocompromised or children. Serious cases requiring hospitalisation are almost exclusively in these risk groups.”
Is this a new / unknown virus or do we already know a lot about hMPV?
“It was first discovered in 2001 but was likely around well before this and not identified. It has been one of numerous common cold viruses that circulate every winter season each year, so no, it is not a new virus.
Do we know this is what is happening in China; do we need more information?
“We know that there has been a surge in infections which have 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, where we are seeing high levels of flu and COVID along with Norovirus. hMPV is usually detected in the winter periods but it does seem that the rates of serious infection may be higher in China than what we would expect in a normal year. We need more information on the specific strain that is circulating to start to understand if this is the usual circulating strains or if the virus causing high infection rates in China has some differences.
Whilst hMPV does mutate and change over time with new strains emerging, it is not a virus that we consider 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, like for COVID-19. Or in the case of influenza, when a totally new variant of the virus enters the human population by combination with a human version of the virus with that of an animal version of the virus from what is known as the animal reservoir. There is no such animal reservoir of related viruses known for hMPV. This means that even if the hMPV in China currently is a new variant of the virus, it is highly likely to be significantly related to previously circulating hMPV strains such that there will be some level of pre-existing immunity from exposure to related viruses previously, which will significantly reduce the disease burden in healthy people. Young people have less developed immune systems and the elderly’s immune systems’ effectiveness has declined from when they were younger, hence they become more susceptible to more serious outcomes of infectious diseases.
Is this unusual in China or does this often happen in winter?
“hMPV is common part of the winter cold causing viruses in most countries with seasonality. It is not usual to be a major concern for high numbers of hospitalisations but it is unclear just how high the numbers are or if issues are arising purely due to coinciding with high flu and COVID levels.
Any other comments about what we do and don’t know about the current situation based on what is being reported?
“hMPV is not a reportable disease and not normally specifically tested for unless a person is hospitalised with complications from cold-like symptoms so surveillance is not as robust and routine in most countries as it is for influenza. Recent years have seen an increase in availability of diagnostic testing for the virus and recent success of the RSV vaccines has led to a significant increase in hMPV vaccine development as success in RSV has given expectation that success in vaccination for hMPV is also possible given it is a virus from the same family. hVIVO’s challenge models played a pivotal role in the development of the RSV vaccines with our studies showing the first human data of clear vaccine efficacy against this important pathogen. Consequently, hVIVO has now developed a hMPV challenge model so that this is available for the research community to help expediate hMPV vaccine development and treatment.”
Prof Peter Openshaw, Professor of Experimental Medicine and Dr Claudia Efstathiou Research Associate, Imperial College London, said:
What is hMPV?
“Human Metapneumovirus. Related viruses cause a condition called ‘Swollen Head Disease of Chickens’ and rhinotracheitis of turkeys, but it’s not clear when metapneumovirus first adapted to human-to-human transmission. hMPV is a distant relative of RSV.
Is this a new / unknown virus or do we already know a lot about hMPV?
“First described in 2001, this awkwardly named common cold virus infects people of all ages. The illness it causes tends to be more severe in those who are very young (aged 1-5 years) or old (over 65). It has similarities to RSV but tends to affect children in the second year of life rather than the first and to peak later in the winter season (especially in older adults, who tend to peak a bit later than toddlers). It can be hard to detect, PCR not being completely reliable. There is no vaccine, but several trials are underway.
Do we know this is what is happening in China; do we need more information?
“More information is always helpful, but there is no evidence so far that what’s being seen in China is much different from what’s being seen in Europe. It seems that it’s the summation of several common winter viral infections rather than a new or unknown virus.
Is this unusual in China or does this often happen in winter?
“There’s the usual co-occurrence of several winter viruses, together causing intense pressure on the healthcare system.
Any other comments about what we do and don’t know about the current situation based on what is being reported?
“Sensible precautions that prevent or reduce the spread of any of these winter viruses would be wise in those with symptoms.”
Prof Sir Andrew Pollard, Director of the Oxford Vaccine Group; Ashall Professor of Infection and Immunity; Pandemic Sciences Institute, University of Oxford, said:
“Human metapneumovirus virus is a common respiratory virus which was first identified almost a quarter of a century ago by Dutch scientists. The virus is known to cause a respiratory Illness in babies and in the elderly which can result in hospitalisation but in most other age groups it simply causes the symptoms of a cold. It is one of the many viruses which circulate in the winter and add to the winter pressures on the NHS. The reports of respiratory infections in China in the past few days appear to be attributed to both influenza and this human meta pneumovirus, which is rather similar to the situation in the UK this week. A vaccine for a similar virus, RSV, was launched by the NHS in 2024 and new vaccines are being developed which could protect against both RSV and human metapneumovirus in one jab.”
Prof John Tregoning, Professor in Vaccine Immunology, Imperial College London, said:
“HMPV (human metapneumovirus) is not a new virus, it was first isolated in 2001 but most likely has been circulating for much longer. It has very similar symptoms (in children at least) to RSV (respiratory syncytial virus). It is part of the cocktail of winter viruses that we are exposed to.
“As with all respiratory viruses, there will be a range of symptoms and severity. Risk factors will include age (either very young or very old) and underlying immunosuppression. Like other viruses it will transmit in coughs, sneezes and in droplets. Protecting yourself by being in well ventilated, covering your mouth when you cough, washing your hands will all help. It will present in the same way as flu, sars-cov-2, RSV, so the same advice applies for those affected – rest, take on fluids, try not to spread it to others. If you do feel very unwell go to your GP. As it is a virus, antibiotics won’t have any effect.”
Prof Paul Hunter, Professor in Medicine, UEA, said:
“Human Metapneumovirus was first really linked to respiratory infections about 25 years ago, but it has been around a lot longer, at least 65 years (https://pmc.ncbi.nlm.nih.gov/articles/PMC5795268/). I supervised a PhD on the infection some years back where we looked particularly at coinfections with other respiratory pathogens.
“hPMV is a quite common respiratory infection that peaks in winter. Almost every child will have at least one infection with hMPV by their fifth birthday and we can expect to go onto to have multiple reinfections throughout life.
“hPMV typically causes cold-like symptoms that recover by themselves within 2 to 5 days. Just occasionally it can cause more severe disease in the elderly, the very young (under 2 years of age) or medically vulnerable. It is one of the leading viral causes of respiratory infections in children under 5 years. There is currently no vaccine and treatment if necessary is basically supportive.
“One of the issues involved in these types of infection is that they are being diagnosed more frequently as we move to molecular diagnostic panels, so it is not always easy to know whether year on year increases are due to actual increases or just because we are diagnosing a greater proportion of infections.
“In England we have seen a fairly marked increase in recent weeks (see here https://ukhsa-dashboard.data.gov.uk/respiratory-viruses/other-respiratory-viruses) – so far the peak % positivity is a little over what it was this time last year so no major difference to usual, unless infections positivity rates continue to increase in coming weeks.
“So overall, I don’t think there is currently any signs of a more serious global issue.”
Declared interests
Prof Martin Michaelis: “No conflicts of interest to declare.”
Dr Andrew Catchpole “Chief Scientific Officer at hVIVO and has no other interests to state.”
Prof Peter Openshaw “I have advised several vaccine companies on the science that underpins vaccine development for hMPV and other respiratory viruses.”
Prof Sir Andrew Pollard: “Professor Pollard is chair of JCVI which provides independent scientific advice on vaccines to DHSC. The comment above is given as Director of the Oxford Vaccine Group, not as JCVI chair.”
Prof John Tregoning: “None for HMPV. In general I do work with Sanofi on flu vaccines.”
Prof Paul Hunter: “No CoIs.”
For all other experts, no reply to our request for DOIs was received.