Australia is reporting high numbers of influenza, respiratory syncytial virus (RSV), and pertussis infections well ahead of winter, with concerns that declining vaccination rates could contribute to a severe respiratory infection season.
More than 54,000 cases of laboratory-confirmed influenza have already been reported nationally this year, which represents a 60% increase from the same period last year. The rates of pertussis infections have also tripled in the first 3 months of this year compared with the same period last year.
“This year, we are going to see a bit of heightened activity of the common respiratory viruses,” Nusrat Homaira, MBBS, PhD, a respiratory epidemiologist at the University of New South Wales in Sydney, told Medscape Medical News.
Influenza is a particular concern, given that the northern hemisphere experienced a severe season during late 2024 and early 2025. The United States has had the highest rate of hospitalizations since 2010 and 2011, and more than 41 million illnesses, 540,000 hospitalizations, and 23,000 deaths have been reported since October 2024.
“As we come into our season, which typically peaks in June to September, what we have seen is increased interseasonal activity for influenza,” said Patrick Reading, PhD, a virologist and director of the World Health Organization (WHO) Collaborating Centre for Reference and Research on Influenza at the Peter Doherty Institute for Infection and Immunity in Melbourne. “Consistently through summer and into autumn, we’ve seen higher levels of cases of lab-confirmed influenza.”
Nusrat noted that some of the increase in notifications might be attributable to increased testing since the beginning of the COVID-19 pandemic. “Because of the pandemic threat, people want to know what they’ve got infected with,” she said.
Australia is also experiencing the biggest outbreak of pertussis since records for the disease began in 1991. A free vaccine is available in Australia for pregnant patients and children, but uptake has been declining for some years, said Paul Griffin, MD, an infectious disease physician, microbiologist, and director of Infectious Diseases at Mater Health Services in Brisbane.
“We know that [the prevalence of] vaccination in pregnancy is probably in the 70%-80% range, which is well below where it needs to be,” Griffin told Medscape Medical News. “And we know that there are some pockets where vaccination is particularly challenging, where the uptake is much lower.”
In Australia’s most populous state, New South Wales, notifications for RSV have been climbing steadily since the start of the year, particularly in children aged 1 year. “RSV activity has also started earlier than expected, so clearly there’s going to be some increased activity of RSV as well,” Homaira said.
Australia has just approved a free RSV vaccine for use in pregnancy, and two monoclonal antibody–based immunizations are available for babies and young children. “The biggest difference with RSV now is we have so many interventions; we just have to focus on utilization,” Griffin said.
Experts say that the greatest threat with respect to respiratory infectious diseases is Australia’s steadily declining vaccination rates for influenza and pertussis.
Julie Leask, PhD, a public health researcher and social scientist specializing in vaccination at the University of Sydney, Sydney, told Medscape Medical News that while there had been a slight decline in confidence in childhood immunization, her own research suggested that the major reason for the decline in vaccination coverage was practical issues associated with accessing convenient and free vaccination services.
“Access to primary care is more difficult now because of pandemic-related workforce barriers and funding models for general practice, which have made general practitioners harder to access and general practice more costly to access,” Leask said. “That is compounded by the increased levels of financial difficulties that families are in now in 2025 compared with before the pandemic.”
Most childhood vaccinations are free, and vaccines against influenza and COVID-19 are free for some people, such as the older adults and those with chronic disease. These vaccines can be administered either within a general practice setting or by a pharmacist.
Many adults weren’t aware that they could or should get an influenza vaccination, said Leask. “Healthcare providers are probably not recommending it as much as they could, and it’s important that they remember that they are very influential when it comes to vaccination.”
Australia is also on alert for measles outbreaks. Sporadic cases have been reported across the country, including 50 cases in the first quarter of 2025. In 2014, the WHO declared that Australia had eliminated measles, but vaccination rates have been declining. “Measles vaccination levels are now below those needed to achieve herd immunity, which increases the risk of local transmission,” said Griffin.
The one piece of good news is that COVID-19 notifications are relatively low, and the average number of COVID-19 cases in intensive care across the country has been decreasing over the past month.
Homaira received funding from MSD Global for research into RSV in children. Reading received funding from the National Health and Medical Research Council for research into an antiviral nasal spray. Leask received funding from the National Health and Medical Research Council for influenza vaccination research. Griffin reported no relevant financial relationships.
Bianca Nogrady is a freelance journalist based in Sydney.