Human metapneumovirus (hMPV) was first ‘discovered’ in 2001 in the Netherlands when researchers found evidence most children had been exposed to the virus by the time they were five years old. The following year, Australian researchers came to the same conclusion: hMPV is very common and often causes the ‘the common cold.’

The illness is most common during the winter months when the seasonal increase of flu-like respiratory illnesses occurs. New technology means we can now much more easily test for viral respiratory illnesses.

Currently, the northern hemisphere – including China – is experiencing an increased prevalence of hMPV and, while this is concerning, the increased prevalence is likely the normal seasonal increase seen in winter. The reported high prevalence amongst children also reflects what we know about this virus: it is a common cause of childhood respiratory illness. Some people can have poor outcomes – like pneumonia – following this respiratory illness and so it is important to try to reduce transmission by staying home when you or your children have flu-like symptoms because hMPV is spread just like other flu-like illnesses – by air-borne droplets produced when an infected person breathes, coughs, or sneezes.

Good hand hygiene, good sneeze and cough etiquette, and wearing a face mask in public places are also important. In Australia, hMPV is not a notifiable disease; however, general surveillance of flu-like illness tells us the current prevalence of these types of illnesses in the community is low and stable.

The recent outbreak of Human Metapneumovirus (HMPV) in China, though not caused by a novel virus, has attracted significant attention due to its rising incidence and potential impact. HMPV poses substantial immunological concerns, especially for vulnerable populations such as young children, the elderly, and immunocompromised individuals. As a respiratory virus, HMPV triggers both innate and adaptive immune responses. The innate response activates interferons and cytokines to control viral replication, while the adaptive response produces virus-specific antibodies and T-cells. However, individuals with weakened immune systems, the very young, or the elderly may have slower or less effective immune responses, increasing the risk of severe complications such as pneumonia, bronchiolitis, or exacerbations of other respiratory conditions.

Repeated exposure to HMPV can lead to partial immunity, making subsequent infections milder. However, secondary bacterial infections complicate treatment, as antibiotics only target bacterial infections, not viral ones. Given the lack of specific antiviral treatments for HMPV, preventive measures like good hygiene practices and the development of anti-virals and vaccines are crucial.

Contributing factors to the outbreak may be due to increased vulnerability to co-infections (such as RSV and influenza), and seasonal/environmental conditions like cold weather, which facilitate viral transmission. While this outbreak isn't linked to a more dangerous strain, the growing number of cases and pressure on healthcare systems in densely populated regions like China highlight the need for enhanced surveillance and prevention strategies. Ensuring effective monitoring and timely responses will be key to mitigating the public health risks of this outbreak.

Human metapneumovirus (hMPV) is a respiratory virus like Influenza and respiratory syncytial virus (RSV). It has been monitored by the Departments of Health in Australia since the 2000s.

However, in late winter and spring of 2023, the cases of hMPV increased especially in NSW. During that period there were more than 1000 cases. The symptoms include cough, blocked or a runny nose with congestion, and shortness of breath and the severity of the infection can vary. In young children, the elderly and those who are immune compromised, hMPV can lead to severe cases and can move to the lower respiratory tract and may lead to pneumonia.

There is no vaccine or treatment for the hMPV, but severe cases are treated in hospital.

In recent weeks China has seen a surge in hMPV cases during the Chinese winter with social media noting crowded hospital emergency rooms. In Australia, we need to use a cautious and measured approach, as we know so much more since the COVID-19 pandemic and take necessary precautions - we need to get tested (do a complete PCR test if you can to know the type of virus), stay home and away from others if having an infection, wear a mask in public and protect our most vulnerable.

Human metapneumovirus (HMPV) is a known important cause of acute respiratory illness, particularly in children and the elderly and can be responsible for seasonal epidemics. The virus was first scientifically described in 2001 but probably circulated in people for many years before that. People can have multiple episodes of infection throughout their lifetime.

This is very different to the COVID-19 pandemic, where the virus was completely new in humans and arose from a spill-over from animals and spread to pandemic levels because there was no prior exposures or protective immunity in the community.

The scientific community also has some understanding of the genetic diversity and epidemiology of HPMV, the kind of impact the virus has on the lungs and established laboratory testing methods - again, very different to the COVID-19 pandemic, where a new lung disease was seen, there was little information on how the virus may vary and spread and we had no initial diagnostic tests.

HMPV can certainly make people very sick, and high case numbers are a threat to effective hospital services, but the current situation in China with high HMPV cases is very different to the threats initially posed by SARS-CoV-2 resulting in the COVID-19 pandemic.

It will be very interesting to learn more about the current circulating HMPV strains, and to see if the simple things we did during the COVID-19 pandemic, such as physical distancing, masking measures and use of rapid antigen testing, can reduce HMPV spread.

China is experiencing a large outbreak of human metapneumovirus (HMPV) cases at the moment. Although this is a priority for China's health system, it should not lead to immediate concerns about a new pandemic.

HMPV is a respiratory virus that was first identified in 2001. It has probably been causing infections in humans for much longer but it needed the correct technology to find it. There is no animal reservoir.

Like many respiratory viruses, it tends to have seasonal peaks of infection (late winter and early spring), although this can vary. As with the current situation in China, children are often worst affected by this virus, but adults with low immune systems and chronic lung or other conditions can get very sick too. There are no licensed vaccines for HMPV but research continues. Similarly, there are no definitive treatments for HMPV infection, but IV antibodies and an antiviral called ribavirin have been used. There are two genotypes (A and B), and variants can occur. At this stage, the likelihood is that China is experiencing a bad HMPV season, in the same way that in some years we have an overwhelming flu season. This could be due to a combination of viral and behavioural factors, but it should settle down.

However, it is also vital for China to share its data on this outbreak in a timely manner. This includes epidemiologic data about who is getting infected. Also, we will need genomic data confirming that HMPV is the culprit, and that there aren't any significant mutations of concern. Such genomic data will also guide vaccine development.