Recorded cases of respiratory syncytial virus (RSV) have nearly doubled on last year across Australia, as a "whole bunch of viruses" continue to circulate throughout the country.
According to the federal government's National Notifiable Diseases Surveillance System, there were 56,063 RSV cases recorded in Australia up to April.
This is nearly double the 29,390 cases recorded at the same time last year.
Last month alone, 24,124 cases were recorded, compared with the 14,286 recorded in April 2023.
NSW has taken on the biggest increase, recording half of all new reports in April, followed by Queensland and Victoria.
And initial data from May shows the numbers are continuing to rise.
Most of these cases are in young children, with nearly three-fifths of diagnoses this year appearing in children four and under.
However, it's impossible to say whether the recorded increase is unusual, because authorities only began collecting consistent national data on RSV from the start of last year.
Increase could be partially due to more testing
University of South Australia epidemiologist Professor Adrian Esterman said the significant increase on last year could be due to more people getting tested for respiratory infections in general.
But he also believes there is more RSV circulating this year compared with last year.
"People are more aware of respiratory diseases and are now more likely to see their GP, and GPs are more aware of respiratory infections and are more likely to get patients tested."" he said.
"But still, there are probably more cases around this year."
The federal government's respiratory surveillance report shares a similar perspective, but says this rise could be due to increased amounts of COVID in the community.
"The higher number of RSV notifications observed in 2024 thus far may be due to an increase in RSV circulation in the community," the government's Australian Respiratory Surveillance Report said.
"But may also be influenced by changes in health-seeking behaviour associated with increases in COVID-19 circulation over the summer period in many jurisdictions, such as increased testing for viral respiratory infections."
This reflects virus surveillance data, which shows COVID has been circulating in high numbers since the start of the year.
Other viruses also circulating
Professor Robert Booy, an infectious diseases paediatrician at the University of Sydney, said RSV has been an issue for the 40 years he's been working in paediatrics.
"We always get a surge in late-autumn and early winter of RSV."
While RSV feels like a mild cold in most cases, it can lead to serious and sometimes deadly illness in young children, the elderly, and immunocompromised individuals.
But aside from RSV, Professor Booy said there have generally been surges of a variety of different bacteria and viruses.
These include whooping cough, where cases have increased this year after very low levels of the virus since COVID, and mycoplasma pneumoniae, a bacteria which causes flu-like symptoms which NSW and Victorian governments have issued alerts for in recent months.
Professor Booy said this was related to COVID restrictions and the reduced movement of people.
"During lockdown, which lasted in places between a year and two years, people had much less exposure to infectious diseases, their immunity wanes, and there was less transmission," he said.
"And so people built up vulnerability to infection, and it's not just RSV or flu – it's a whole bunch of viruses."
"So we're dealing with a lot of different infections, currently, and with the winter season, where people spend more time inside, there's even more transmission of various infections."
Lower vaccination rates
Federal government data shows vaccination rates for viruses are generally lower this year compared with last year.
COVID vaccination rates have also softened, and RSV vaccines have recently been made available to Australians, but not widely so.
Professor Esterman said the lower vaccination rate was likely due to hesitancy.
But he insisted older and vulnerable Australians should continue to protect themselves from respiratory illnesses through vaccination and mask-wearing.
"The majority of people simply aren't going to care, and unfortunately, this spreads the disease," he said.
"Elderly people need to protect themselves with vaccines, and they need to get their COVID and flu vaccine up to date."
Australian Medical Association president Steve Robson said despite "vaccination fatigue", it was really important for people to book in their jab because there were signs "it could be a bad winter".
"COVID is still taking lives, influenza is still taking lives," he said.
"It's not too late — we're just hitting the flu season, and it could be a decision that saves your life."
Calls for RSV infant vax to be made available
The Royal Australian College of General Practitioners has also called on the Victorian, Tasmanian and South Australian governments to make RSV immunisation free for vulnerable infants.
Western Australia and Queensland are offering it to all infants in their first year of life, while NSW is just offering it to medically vulnerable babies.
Anita Muñoz, the chair of the RACGP Victoria, said currently, families in Victoria had to fund the vaccine for their baby themselves.
"I certainly think there is a great sense of urgency," Dr Muñoz said.
"When we think that RSV-associated infections can cause babies who are at risk to go into hospital, we think it's very worthwhile to be protecting them."
