Human metapneumovirus is spreading in NSW

(ABC) -- NSW Health has recorded a spike in cases of a lesser-known respiratory virus.
Human metapneumovirus (HMPV) has been on the medical radar since the early 2000s and NSW authorities say the number of weekly cases has jumped from 648 at the beginning of the month to 1,168 in the week ending September 17.

Dr Kerry Chant said there has been a resurgence of respiratory viruses as COVID safety measures were eased. --Photo  ABC

According to NSW Health, HMPV is normally more common in late winter and spring.
This is what you need to know about the virus, and why we are seeing so many cases at the moment.
University of Sydney senior researcher and virologist John-Sebastian Eden said the symptoms aren’t that different to that of a common cold.
Its symptoms are very similar to that of COVID-19, the flu and respiratory syncytial virus (RSV), which is genetically similar to HMPV.
“For most healthy adults, you probably wouldn’t be a differentiator from COVID or flu … or just really having a cold or having a bad cough,” he said.
Dr Eden said people were unlikely to know of the virus until they tested positive to it.
“It’s definitely one of the viruses that you probably don’t know about until you just happen to have that test where you see a report that says, you had HMPV, you might have thought it was flu or COVID.”
Testing for the virus is done via a PCR (polymerase chain reaction) test, however not all PCRs will test specifically for HMPV.
NSW Health advice is to:
- Stay home if you have cold or flu symptoms
- Wash or sanitise your hands often
- Wear a mask in crowded, indoor places
- Get together outdoors or in large, well-ventilated spaces with open doors and windows
- Don’t visit people who are at higher risk of severe illness if you have cold or flu symptoms.
Virologist at the University of New South Wales, Professor William Rawlinson, said the medical community had a strong consensus that masks are effective for slowing the spread of respiratory illness, but a mix of responses were needed.
Dr Eden said there are no anti-viral drugs used to treat HMPV, nor is there a vaccine.
“There’s no specific drugs for these viruses. So it’s just managing the symptoms until the immune system kicks in and takes care of the virus,” he said.
“If you’re sick, stay at home, wash your hands, look after your kids if they’ve got some infection or something like that, and just staying away from other people if you’ve got a respiratory infection.”
Sicker, older and younger people most at risk
Although HMPV is usually a mild cold for most people, the virus can occasionally escalate and become more serious with young children, older adults and those with compromised immune systems most susceptible, according to NSW Health.
Dr Eden said for children below five years of age, there is a risk of complication.
“In young kids, it can lead to some kind of chronic inflammatory diseases after infection.”
HMPV can also cause severe disease if contracted by the elderly, he said.
“We’ve had noted outbreaks in previous years at nursing homes … so it can really cover the whole spectrum,” Dr Eden said.
“But for the vast majority of people, it’s something that you might battle for a week and then get over.”
Professor Rawlinson said viruses like HMPV can develop into other respiratory sickness like pneumonia, but it is very unlikely.
“Some of those [cases] can then progress and in people with particularly compromised immunity, they can then progress in some cases to die, although that’s uncommon with HMPV.”
Health officials said it’s possible there’s an underestimation of the number of cases in the community because of the test samples that come back.
Health Minister Ryan Park echoed the department’s sentiment.
“People don’t need to be alarmed but they do need to be informed and what that means is making sure that they’re aware that this virus is around and that if they’re starting to show the symptoms then do what they would normally do for a cold and flu.”
Why are there more cases?
While HMPV tends to be more common towards the end of winter into spring, NSW Chief Health Officer Kerry Chant said the vigilance during the height of the COVID pandemic meant people took measures that slowed the transmission of many viruses.
“What we’re seeing is the resurgence of respiratory viruses. For the first two years of the pandemic we basically have very little circulation of respiratory viruses because of all those COVID social distancing measures,” Dr Chant said.
“We’ve now seen an uptick in as we’ve seen flu, RSV and HMPV is yet another virus.”
Professor Rawlinson said researchers are still not sure why the virus is more common at this time of year.
“It’s probably that people are coming out and mixing more, it’s probably spread rather than the virus itself,” he said.
“But it’s a very good question. It’s one of the things that we need to research.”

(Latest Update September 28, 2023)