Explainer: RSV may not quite have the name recognition that influenza and Covid do, but it's actually causing more winter illness.New Zealand has some of the world's highest rates of serious illness caused by the virus, and health experts are calling for a national childhood vaccination programme to be instituted.The Public Health Communication Centre issued a briefing this week asking for the government to approve RSV vaccines being used in Australia and other countries, which it says will also relieve the enormous burden put on doctors and hospitals each winter."It's an awful experience for families to see their children struggling to breathe," Emma Best, an associate professor of paediatric and youth health at Auckland University, told RNZ's Morning Report.What exactly is RSV?Dr Hasan Bhally is an infectious diseases specialistSuppliedRespiratory syncytial virus - RSV for short - is exceedingly common, particularly in the winter months from May to October.It causes infections in the lung and respiratory tract. For some people it'll have symptoms similar to the common cold and fade after 10 days or so.But for children and older people with compromised immunity, it can be much more serious.Dr Hasan Bhally, an infectious disease doctor at North Shore Hospital, told RNZ's Nine To Noon that RSV is actually causing more cases than Covid-19 or influenza according to recent data."RSV is the most common of those troublesome three with about 45 percent, versus 25 percent for Covid and 30 percent for influenza.""When you look at the viruses being seen over the last weeks amongst hospitalised people, RSV is much more than flu at the moment," Best added.RSV spreads through the air when people sneeze or cough. People are typically infectious for about 10 days after symptoms have started.There's plenty of chatter on social media about people suffering long illnesses lately, and much of that could be attributed to RSV, Best said."With RSV peaking at the moment it is likely the cause of the comment 'a lot of people talking about being sick recently,'" she noted.The Respiratory Illness Dashboard run by PHF Science shows a steady rise in illnesses typically reported through July and into September.Currently trends are "rising toward high so not at peak winter illnesses yet," Best said.Is it worse for children?Around 1800 to 2000 children every year are hospitalised with RSV, the Public Health Communication Centre report said.About half of those are infants, particularly those under 6 months."Beyond the immediate illness, there is increasing evidence that RSV infection in infancy is associated with recurrent preschool wheeze and asthma, further adding to the long-term burden on families and the health system," the report noted.RSV so far isn't actually worse than in previous years, but it is rising at typical levels for winter."It is predictably high at this time of year and leading to children under 5 and particularly under 1 being hospitalised," Best said.Māori and Pasifika children are three to five times more likely to be hospitalised, the Cardiac and Respiratory Foundation NZ says.Thousands of babies born each year "are healthy but acquire RSV, have an awful wheezing illness, they need oxygen, they need support with their feeding, they need hospitalisation essentially," Best said."It's really predictable for us, we see RSV coming, beds are full in hospitals."But adults can get it too?Definitely, and it can cause life-threatening complications."It is true that it's predominantly a virus of babies, especially infants, but there is a significant burden in adults also, especially the older adults, which I will define as 65 years and more," Bhally said."Our immunity wanes from natural infections as we all age," he explained.Adults who have chronic health problems like asthma are also highly at risk, he said."Infections in these people can be quite severe, meaning it can lead to hospitalisation."Babies are particularly affected by RSV.123RFHow is it treated?"There's unfortunately no antiviral treatment for RSV," Bhally said.Because it's a viral infection, not bacterial, antibiotics don't work on RSV.For adults the general recommendations is to isolate yourself, drink fluids, rest and take painkillers as needed.For children, it's important to monitor their health closely - infants may not show symptoms as obviously as adults.A medicine called palivizumab is available for some infants and children who are at high risk of severe illness, Health NZ says. Palivizumab is given by injections repeated once a month during the RSV season. A healthcare provider can determine if a child is eligible.Anyone who shows signs of trouble breathing should seek immediate medical attention, as complications like pneumonia or bronchiolitis can develop.Is there a vaccine?There's no universal childhood vaccine programme in New Zealand, although there are growing calls to start one.There are childhood vaccines already available in the US, UK, and Australia, but they have not yet been approved for use in New Zealand yet, a fact which has angered medical experts."We just feel disappointed really, because it's been almost two years now in Australia that they've had some prevention for RSV," Best said.In Australia, the ABC reported New South Wales are hailing the vaccination program launched in 2024 that's nearly halved hospitalisations ahead of the winter peak as a "fantastic" success.Vaccines for RSV are relatively recent developments - there are long-acting monoclonal antibodies given to newborns, and maternal vaccination given during pregnancy."The landscape of RSV vaccinations is changing rapidly," Bhally said. "It's very exciting times if we look at what's happening globally with RSV vaccinations.""We have to make the vaccines available, funded and accessible," he said.Both Best and Dr Bhally called upon the government to approve and fund them for use in New Zealand."These have been licensed in Europe, US and Australia for several years already, so again we don't know why these things take longer when we've already got international agencies that have licensed them," Best said.There is also a vaccine aimed at adults over 60 or those between 50 to 59 who are at increased risk, called Arexvy.However, it's not funded by Pharmac and runs more than $400."RSV is unfortunately, one of those viruses that in older adults it does have a mortality ranging from 4 to 8 percent, so it is a serious disease," Bhally said.