Measles Cases Spike in NSW Amidst Concerns of Undetected Community Spread
A concerning rise in measles cases in New South Wales (NSW) has health authorities on high alert, with a significant portion of recent infections showing no clear link to overseas travel or known exposure sites. This suggests the highly contagious disease may be circulating silently within the community, a scenario that poses a substantial risk for a wider outbreak.
In the first three months of this year, NSW recorded 38 measles cases. Alarmingly, five of these cases have no identifiable source of infection, according to Vicky Sheppeard, director of the South Eastern Sydney Local Health District’s Public Health Unit. While the majority of cases are attributed to returned travellers from Southeast Asian countries, these untraceable infections are a significant cause for concern.
“That is of concern because there must have been undetected cases,” Dr. Sheppeard stated. “In order to prevent an outbreak, we need to identify all cases and make sure that all their contacts are followed up.”
Measles, a potentially fatal but preventable disease through vaccination, typically presents with a fever, cough, and a distinctive rash that can spread across the entire body. While most recover, severe complications can include middle-ear infections, diarrhoea, and pneumonia. In rare and tragic instances, it can lead to subacute sclerosing panencephalitis, a progressive and fatal brain disease.
The Link to International Travel and Shifting Vaccination Patterns
Dr. Sheppeard explained that an annual increase in measles cases is often observed in the early months of the year, coinciding with the return of travellers from abroad. The current surge in 2026 is notably higher than in previous years, a trend linked to significant measles outbreaks in Southeast Asian nations such as Indonesia, Vietnam, and the Philippines, which have experienced heightened activity since the COVID-19 pandemic.
“Australians love to travel to south-east Asia and do that frequently, particularly over the summer period,” Dr. Sheppeard noted.
The detected cases have predominantly affected Australians in their 20s and 40s. This demographic observation may be linked to changes in vaccine scheduling and potentially less rigorous childhood immunisation protocols in the past. Historically, the measles-mumps-rubella (MMR) vaccine was recommended with a first dose at 12 months of age and a second at 18 months. However, in response to rising global measles activity, the Australian Technical Advisory Group on Immunisation (ATAGI) updated its advice in January to recommend an additional dose for infants aged six to 11 months if travelling overseas.
Despite these international challenges, Australia benefits from a robust public health infrastructure. “In Australia, we’re really lucky we have had a long-standing national immunisation program that funds our vaccines,” Dr. Sheppeard highlighted. “We’ve got a strong public health sector, we have Medicare and we have a national register, so that has enabled us to really maximise our coverage.”
Australia’s Measles-Free Status Under Scrutiny
Australia was declared to have eliminated endemic measles by the World Health Organisation (WHO) in 2014. However, this hard-won status is facing increasing pressure globally. In recent years, numerous countries, including the United Kingdom, Spain, and Canada, have lost their elimination status due to uncontrolled outbreaks and declining vaccination rates. The United States, which first achieved elimination in 2000, is now at risk of losing its status, with outbreaks reported in over 40 states.
Catherine Bennett, Chair of Epidemiology at Deakin University, acknowledges that Australia’s current level of local transmission is not comparable to that seen in the US or Southeast Asian countries. Nevertheless, she cautions that a sustained decline in vaccination rates, coupled with a lack of response to international outbreaks, could jeopardise Australia’s elimination status.
“If [cases] are all imported that’s telling us about endemic disease in other parts of the world that haven’t eliminated it,” Professor Bennett explained. “But if we have enough unvaccinated people and enough secondary cases in Australia particularly, that then start passing it on to other people — then it changes the whole dynamic.”
Professor Bennett pointed to the US as an example where “local explosions” of measles are occurring, driven not only by geographical factors but also by varying religious and cultural perspectives on vaccination. “If measles gets into part of the community where it starts to spread because there’s enough susceptible people who aren’t vaccinated or haven’t had a prior infection, then that’s when local transmission starts to take off,” she stated. “It’s a disease that, thankfully has a relatively low fatality rate, but the most fatalities occur in children.”
The Crucial Role of Vaccination in Maintaining Herd Immunity
Achieving herd immunity, the point at which enough of a population is immune to prevent widespread disease transmission, requires vaccine coverage of 92–94 per cent, according to the Department of Health. Recent data from the National Centre for Immunisation Research and Surveillance indicates a slight decrease in the coverage of the first dose of the MMR vaccine in children at 24 months of age, dropping by 0.4 of a percentage point between 2022 and 2023.
Terry Slevin, chief executive of the Public Health Association of Australia, described measles as a critical indicator, or “canary in the coal mine,” for the health of the nation’s infectious disease control. While Australia has historically maintained high vaccination rates, there’s a gradual decline that is bringing coverage below the national target of 95 per cent.
“We know measles is a highly infectious disease and ultimately our best defence is a very, very effective vaccination regime,” Adjunct Professor Slevin emphasised. “In most cohorts, we have in excess of 90 per cent take-up, it’s slightly coming off from the target.”
He further noted that preventing the introduction of travel-related infections is nearly impossible, particularly as measles can be asymptomatic in its early stages. “Australians travelling overseas or people coming from overseas into Australia, and bringing the infection with them — ultimately it comes down to issues relating to regions around the world having varying levels of vaccination,” he said.
However, Adjunct Professor Slevin remains cautiously optimistic. “I don’t think there’s reason to be concerned about our disease-free status being removed as long as we respond to these challenges sensibly and continue to reinforce the importance and value of vaccination in Australia.”
