Table of Contents
Australia is facing an outbreak of whooping cough.
In the first three months of 2024, some 2,799 cases were registered.
Cases are highest in Queensland and New South Wales, with more than 1,000 recorded in each state.
The last time Queensland recorded more than 1,000 cases in three months was in the first quarter of 2013.
This was at the end of a major outbreak that stretched from 2008 to 2012 – the largest outbreak reported in Australia since the widespread introduction of pertussis vaccines in the 1950s.
More than 140,000 cases were recorded during this period, with the figure peaking at 38,748 in 2011.
There was a minor 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 more dangerous for babies
Whooping cough can be life-threatening for newborns who have not received their vaccines.
Whooping cough is a serious and highly contagious respiratory disease. Also called whooping cough, it is caused by the bacteria Bordetella pertussis.
The initial symptoms of whooping cough resemble other cold- and flu-like symptoms. These include a runny nose, sneezing, mild cough, and fever.
However, as the illness progresses into the second week, the coughing attacks become worse and more frequent.
After or between coughing attacks, patients may gasp for air and produce the characteristic “screaming” noise.
The illness is also sometimes called “100-day cough” because it can last 6 to 12 weeks.
It is especially serious and can be life-threatening for newborns who have not yet received their vaccines.
In older children who are fully vaccinated, as well as in adolescents and adults, the disease is usually less severe.
However, even in adults, coughing can lead to rib fractures.
Antibiotics are used to treat whooping cough, but they are most effective when given during the initial stages of the disease.
The best protection in the first instance is vaccination, which prevents most cases of serious illness and reduces the spread of whooping cough in the community.
It is recommended that children receive six doses of pertussis vaccine (which is combined with vaccines for other diseases) between the ages of about two months and 13 years.
Vaccination is free under the National Immunization Program for children and pregnant women. Vaccinating women against whooping cough during pregnancy protects newborns in their first months of life.
Immunity from these vaccines wanes over time, so it is also recommended that adults receive a booster, especially those who may come into frequent contact with babies.
Why are cases increasing now?
Whooping cough outbreaks usually occur every three to four years. Due to COVID measures such as border closures, social isolation and the use of masks, the number of cases decreased dramatically during 2020-23. If trends had followed the usual outbreak cycle, this might have been the time we would have seen another outbreak.
The omission of routine pertussis vaccinations at the height of the pandemic may mean Australia is more vulnerable now.
Reduced immunity in the population could be one of the reasons why we are seeing an increase in whooping cough cases in Australia and other countries, including the United Kingdom and the United States.
In Australia, cases have been particularly high during this outbreak in children aged 10 to 14 years.
A potential superbug
Over the past two decades, whooping cough has improved in its ability to evade vaccines and antibiotics.
Most vaccines used in Australia and other developed countries stimulate the immune system to recognize and target between three and five components of the bacteria.
Over time, the bacteria that causes whooping cough have slowly acquired mutations in these genes. These mutations make the bacteria look slightly different than the one used in the vaccine, which helps it hide better from the immune system.
There are fears that the pertussis bacteria Bordetella pertussis could become resistant to antibiotics.
Most of these changes were small. 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 his immune system, like a detective, has one less clue to recognize bacteria.
This new strain rapidly rose from 5 percent of strains found in 2008 to becoming the dominant strain in less than ten years, accounting for 90 percent of strains in 2017.
This pertactin-negative strain was shown to survive better in vaccinated mice and may have contributed to the high number of cases in the 2008-2012 outbreak.
Worryingly, since 2013, antibiotic-resistant strains of whooping cough have become widespread in China.
While other antibiotics are available, they are not recommended for babies younger than two months (the age group most at risk for severe illness). These resistant strains are increasingly spreading across Asia, but are not yet in Australia.
Whats Next?
It is too early to know how large this outbreak will be or what strains are responsible for it. Greater monitoring of whooping cough strains, as we do with COVID, is needed to inform future vaccine design and treatments.
Importantly, although the bacteria is evolving, current vaccines are still very effective at preventing serious illness and reducing transmission. They remain our best tool to limit this outbreak.
To protect yourself, vulnerable newborns, and the community at large, everyone should make sure they are up to date on their pertussis vaccines. You can check this with your GP if you are unsure. And anyone with cold or flu symptoms should stay away from babies.
Laurence Don Wai Luu is a Professor and Chancellor’s Research Fellow in the Faculty of Life Sciences at the University of Technology Sydney. This article was originally published in The conversation