The surge of viral infections seen in NSW is due to human metapneumovirus (hMPV), a virus that affects the respiratory system but many people may not be familiar with. In fact, hMPV has just been discovered in humans in 2001 by a group of researchers in the Netherlands.

Human metapneumovirus infections pose an important threat to the health of infants, elderly, and immunocompromised people, such as transplant patients, who are most at risk of contracting hMPV, and developing severe disease, such as pneumonia or bronchiolitis.

hMPV infections are not endemic to any particular region but occur periodically around the world. The infection peak for hMPV is usually seen at the end of winter and early spring. Global studies have indicated that every child under the age of five has encountered hMPV at one point in their life, with the percentage of children who are hospitalised due to an hMPV infection being 10-12%.

Although there have been many advances made since its discovery, neither effective drugs nor vaccines are currently available to treat or prevent hMPV infections.

At the Institute for Glycomics, our research focuses on how hMPV is able to bind to human cells and how the virus spreads in the human body. It has been already identified that one viral protein is essential in the lifecycle of hMPV and we are trying to understand how this protein interacts with the human host cell receptors. We then utilise this information to design effective drugs that can block the interaction between the viral protein and human host cell receptors, therefore preventing disease.

hMPV has been misconstrued as a 'new' virus because it was discovered in 2001. However, hMPV likely infected humans for decades if not centuries before its discovery- we just didn’t have the technology to identify it as the cause of common respiratory illnesses. This is very different from SARS-CoV-2, which did not infect humans before 2019. Because it is highly likely that most Australian adults have been infected with hMPV before, we have some level of immunity against it. This was not the case for SARS-CoV-2 because our immune systems had no previous experience with that virus when we were first infected.

What we are currently experiencing in NSW is in line with epidemiological patterns in other parts of the world. Cases of hMPV spiked in the United States around March of this year, at the end of winter and beginning of spring. This was likely due in part to increased testing, but a study in the Lancet Microbe found that concentrations of hMPV in wastewater in California also increased. This suggests that there was a bona fide rise in hMPV cases along with other respiratory viruses. We are witnessing a similar pattern of cases here in NSW as we enter spring. Although we should take this seriously, as vulnerable populations including children and the elderly can experience severe disease from hMPV infection, there is no reason to think that what is happening here is an anomaly.

Human Metapneumovirus has been recognised since 2001 and has been in many respiratory testing panels for a long time.

The virus is not a notifiable infection, according to SA Health.

It is probably always around and most frequent around winter/early spring as for RSV.

Clinically and epidemiologically, it is similar to RSV, and along with RSV and influenza, is one of the leading causes of respiratory tract infections in children.  

More recently (in the past 10 years or so) it has been more recognised in adults and the elderly, and as a cause of pneumonia in immuno-suppressed people where it can cause quite severe disease. There is no specific treatment other than supportive, and there are no vaccines currently available.  

Given the recent success with the development of RSV vaccines (including with mRNA technology) it is likely that this will spur interest in metapneumovirus vaccine development.

While we are talking more about it currently, human metapneumovirus or hMPV is not new. There are lots of things that influence how much we report and discuss viruses like this, particularly at the moment, including that aggressive COVID mitigating strategies influenced a number of other viruses including hMPV, so numbers were lower, particularly in 2020. Recently our focus was almost solely on COVID testing, then COVID plus flu, and then also RSV. Rapid antigen tests don't find hMPV at present but when people do get a full respiratory virus PCR panel at a laboratory our ability to find hMPV has actually improved.

We currently do not have any vaccine or treatment for hMPV but fortunately, most people will recover relatively rapidly without any intervention. Basic infection control practices, including staying home if you're unwell, good hand hygiene, and mask-wearing work for this virus as well. The reason why it's important there is awareness regarding this virus at the moment is that it does seem to be on the rise, which is not the first time we've seen this but is a little unusual this time of year. While more common in children, it can cause more severe disease in vulnerable people, particularly the immunosuppressed and elderly people with comorbidities.

It is also a virus that is prone to causing outbreaks in nursing homes and hospitals, so identifying it early and implementing appropriate precautions is very important. Another key takeaway is that if you are unwell and test negative for COVID, flu and even RSV, it's still important to take precautions, particularly staying away from others, until your symptoms settle. Also consider getting a full respiratory virus PCR panel via a laboratory to identify what you are infected with.

Human metapneumovirus is a well-known respiratory virus like influenza and RSV and we see children commonly affected with this virus. However, since the emergence of COVID-19 pandemic, seasonality and distribution patterns for common respiratory viruses have been altered and there has been increased detection as well.

Like any other respiratory virus, we should consider keeping our children at home if they have respiratory symptoms, maintain respiratory hygiene and practice frequent hand washing to prevent transmission of respiratory infection.

Despite the ongoing circulation of respiratory viruses, including COVID-19, the population is moving away from adhering to the infection control measures we learnt during the height of the recent pandemic. Mask-wearing is increasingly rare and social distancing largely non-existent as the community re-engages with the social activities and events largely missed for the past three years.

As a result, there has been a resurgence of all respiratory illnesses, including hMPV and RSV, over recent months. However, as we near the festive season, it is a timely reminder we should all continue with the good habits we learnt during the pandemic, including good cough and sneeze hygiene, to avoid social gatherings if we have any respiratory symptoms, and – if we have to head out while sniffly – to wear a mask in public.