Overview of Measles

As of early May 2025, Australia has reported 70 cases of measles across various states and territories, with the exception of Tasmania and the Australian Capital Territory. The majority of these infections have been recorded in New South Wales, Victoria, and Western Australia. This figure has already exceeded the total cases reported in 2023 and 2024, indicating a concerning trend in measles outbreaks, which are occurring globally.

Many cases in Australia involve travelers returning from overseas, particularly from popular destinations in Southeast Asia. Although local transmission of measles was eliminated in Australia in 2014, there have been recent instances of community transmission, suggesting that the virus is circulating within the population.

1. Defining Measles

Measles is one of the most contagious diseases affecting humans, with an infected individual capable of spreading the virus to 12 to 18 people who are not immune. The virus can linger in the air for up to two hours, allowing for transmission even after the infected person has exited an area. It predominantly impacts young children and individuals with weakened immune systems, leading to hospitalizations for nearly 40% of those infected, and fatalities in approximately three out of every 1,000 cases. In 2023 alone, over 100,000 deaths due to measles were reported globally.

2. Recognizing Symptoms

Symptoms of measles typically manifest 7 to 14 days following exposure to the virus. Initial symptoms include fever, cough, a runny nose, conjunctivitis, and a distinctive rash. The rash often begins on the face or neck and can spread to the rest of the body within three days, potentially making it less visible on darker skin tones. Complications from measles, such as ear infections, encephalitis, and pneumonia, are common, particularly among children. Pregnant women also face heightened risks, including preterm labor and stillbirth.

3. Distinguishing Measles from Chickenpox

Measles and chickenpox are caused by different viruses, though both affect children and can be prevented through vaccination. Chickenpox, caused by the varicella zoster virus, presents with a rash that typically starts on the chest or back as red bumps, progressing to fluid-filled blisters. Unlike measles, chickenpox can lead to shingles later in life.

4. Immunity to Measles

Once a person contracts measles, they develop lifelong immunity to the virus. In Australia, individuals born prior to 1966 likely experienced measles before the vaccine was introduced and are thus protected. However, measles infection can impair the immune system's ability to recognize previously encountered infections, which is why vaccination is crucial.

5. Vaccination Details

The measles vaccine contains a weakened form of the virus and is typically administered as part of a combination vaccine that also includes mumps and rubella (MMR) or chickenpox (MMRV). Children in Australia receive their first dose at 12 months and a second at 18 months. It is possible to administer the vaccine earlier, around six months, for infants at higher risk of exposure. Adults born between 1966 and 1994 may require an additional dose due to changes in vaccination recommendations during their childhood.

6. Duration of Vaccine Efficacy

The measles vaccine is recognized as one of the most effective vaccines, providing lifelong immunity to about 99% of individuals who receive two doses. Moreover, vaccinated individuals not only protect themselves but also prevent the spread of the virus to others.