How a deadly disease most dangerous to babies is sweeping Australia – and what you can do about it

Australia is facing an outbreak of whooping cough.

About 2,799 cases were recorded in the first three months of 2024.

The number of cases is highest in Queensland and New South Wales, with more than 1,000 cases recorded in each state.

The last time Queensland recorded more than a thousand cases in three months was the first quarter of 2013.

This was the tail end of a significant outbreak that stretched from 2008 to 2012 – the largest reported outbreak in Australia since the widespread introduction of whooping cough vaccines in the 1950s.

More than 140,000 cases were registered during this period, with a peak of 38,748 in 2011.

There was a smaller outbreak between 2014 and 2017, with more than 60,000 cases in these years.

So what is whooping cough, why are cases increasing now and how can you protect yourself?

Whooping cough is most dangerous for babies

Whooping cough is a serious and highly contagious respiratory disease. Also called whooping cough, it is caused by the bacteria Bordetella pertussis.

The first symptoms of whooping cough are similar to other cold and flu-like symptoms. These include runny nose, sneezing, mild cough and fever.

However, as the disease progresses into the second week, the coughing fits become worse and more frequent.

After or between coughing fits, patients may gasp for air and produce the characteristic ‘whoop’ sound.

The disease is also called the ‘100-day cough’ because it can last six to twelve weeks.

It is especially serious and can be life-threatening in newborns who have yet to receive their vaccinations.

In older children who have been fully vaccinated, as well as in adolescents and adults, the disease is normally less severe.

But even in adults, coughing can lead to broken ribs.

Antibiotics are used to treat whooping cough, but are most effective when given during the early stages of the disease.

The best initial protection is vaccination, which prevents most cases of serious disease and reduces the spread of whooping cough in the community.

It is recommended that children between the ages of about two months and thirteen years receive six doses of a whooping cough vaccine (which is combined with vaccines for other diseases).

Vaccination is free under the National Immunization Program for children and pregnant women. Vaccinating women against whooping cough during pregnancy protects newborns in the first months of life.

Immunity to these vaccines wanes over time, so it is also recommended that adults get a booster, especially those who often come into contact with infants.

Why are cases increasing now?

Outbreaks of whooping cough typically occur every three to four years. Due to COVID measures such as border closures, social isolation and masks, the number of cases has fallen dramatically in the period 2020-2023. If the trends had followed the usual outbreak cycle, this would have been around the time we would have seen a new outbreak.

Missed routine whooping cough vaccinations at the height of the pandemic could mean Australia is now more vulnerable.

Reduced immunity in the population could be one of the reasons we are seeing a rise in whooping cough cases in Australia and other countries, including the UK and the US.

In Australia, cases during this outbreak were particularly high among children aged 10 to 14 years.

A potential superbug

Over the past twenty years, whooping cough has become increasingly adept at evading vaccines and antibiotics.

Most vaccines used in Australia and other developed countries stimulate your immune system to recognize and attack three to five components of the bacteria.

Over time, the bacteria that causes whooping cough slowly acquired mutations in these genes. These mutations make the bacteria look slightly different from the bacteria used in the vaccine, making them better able to hide from the immune system.

Most of these changes were minor. But in 2008, a new strain appeared in Australia that no longer produced pertactin, one of the components targeted by the vaccine. This means that your immune system, like a detective, has one less clue to recognize the bacteria.

This new species quickly grew from 5 percent of the species found in 2008 to become the dominant species in less than a decade, making up 90 percent of the species in 2017.

This pertactin-negative strain appeared to survive better in vaccinated mice and may have contributed to the high number of cases during the 2008-2012 outbreak.

Worryingly, antibiotic-resistant strains of whooping cough have become widespread in China since 2013.

Although other antibiotics are available, they are not recommended for infants under two months of age (the age group most at risk of serious illness). These resistant species are increasingly spreading through Asia, but are not yet present in Australia.

What now?

It is still too early to know how big this outbreak will be and which species are responsible. Better monitoring of whooping cough variants, as we are doing with COVID, is needed to inform future vaccine designs and treatments.

Importantly, although the bacteria are evolving, current vaccines are still highly effective at preventing serious disease and reducing transmission. They remain our best tool to limit this outbreak.

To protect themselves, vulnerable newborns and the wider community, everyone should ensure they are up to date with their whooping cough vaccinations. If you are not sure, you can ask your doctor. And anyone with cold or flu-like symptoms should stay away from babies.

Laurence Don Wai Luu is a lecturer and chancellor researcher at the School of Life Sciences, University of Technology, Sydney. This article was originally published on The conversation