Australia sees surge in whooping cough cases across the country, making it on track to be its worst whooping cough year since 2016

Australia is experiencing an ongoing whooping cough outbreak, with more than 11,000 cases in the past six months, up from 2,447 cases last year.

This highly contagious disease is most dangerous for infants under six months of age who are too young to be vaccinated.

In adults, whooping cough initially feels like a bad cold or flu, increasing the risk of community-acquired transmission.

Previous outbreaks have shown that new, “smart” strains are evolving that can evade vaccines.

So how bad could this outbreak get, and what can we do to protect ourselves and protect those most vulnerable?

How to identify whooping cough

Whooping cough is a serious respiratory disease caused by the bacteria Bordetella pertussis.

It starts with typical cold or flu symptoms such as a runny nose, sneezing, mild cough and fever.

Therefore, in the early stages, it can be difficult to distinguish it from any other severe cold.

However, after about a week or two, the coughing attacks become more frequent and severe and may cause vomiting and broken ribs.

The cough can last up to 12 weeks, which is why it is sometimes called the “100-day cough.”

Some older children and adults do not produce the characteristic whistling sound that occurs when they gasp for breath.

That's why Lawrence Lu, a microbiologist at the University of New South Wales, says people should try to get tested early.

The disease is highly contagious and easily spread by adults who are unaware they are infected.

“There are antibiotics that can treat it but they need to be taken early, so it's important to get tested early,” he said.

The disease is most dangerous for infants, with about one in three babies under 12 months old being hospitalized, Dr. Lu said.

Newborns may not cough, but they may stop breathing or turn blue in the face.

On the other hand, some babies may have difficulty feeding or choke when coughing.

People over 65 are also at higher risk of developing severe symptoms.

“Your immune system will be busy attacking whooping cough, making you more susceptible to other secondary respiratory infections,” Dr. Lu said.

It can lead to pneumonia, brain damage and even death.

About 1 in 125 babies under six months who catch whooping cough die from pneumonia or brain damage, according to the Australian Institute of Health and Welfare.

Why is the infection spreading?

Dr. Lu said large whooping cough outbreaks occur cyclically, occurring approximately every three to four years.

After a large cycle of infection, more of the population will become immune, but after a few years this immunity will begin to wane.

“We're going to see a surge in cases, then a decline for a few years, then a rise again,” he said.

The last big spike was around 2017, so the next one was expected to happen around 2020, but was postponed due to the COVID-19 pandemic.

And now the number of infections is exploding even further.

“This is shaping up to be the worst year for whooping cough since 2015-2016,” Dr. Lu said.

Australia reported its largest pertussis outbreak since the widespread introduction of the pertussis vaccine between 2008 and 2012.

More than 140,000 cases were recorded during this period, with numbers peaking at almost 40,000 in 2011.

Dr Peter Richmond, chair of paediatrics at the University of Western Australia, said Australia appeared to be heading for the next wave.

“It certainly seems like we're moving in that direction,” he said.

Some 11,473 cases of whooping cough have been recorded in Australia so far this year, according to the Department of Health's National Notifiable Disease Surveillance System (NNDSS).

Currently in Queensland and New South Wales It has seen the biggest increase in cases so far.

“We are beginning to see an increase in cases in Victoria and we are beginning to see an increase in other states as well,” Professor Richmond said.

“This started late last year and is really causing problems now, especially among school-age children.”

Previous outbreaks have mainly affected young children.

This time, the number of infections is particularly high among children aged 10 to 14, and there is currently an increase in infections among children under the age of one.

Dr Lu said a lack of routine whooping cough vaccination during the pandemic and fewer opportunities to contract the disease could mean certain groups are more susceptible to infection.

It is recommended that children receive six doses of the whooping cough vaccine between the ages of about six weeks and 13 years of age.

The threat of new mutant strains

Australia is not the only country seeing a surge in infections.

Whooping cough has resurfaced in the United States, the United Kingdom, Europe and China after a pandemic.

China saw more than 30,000 cases in the first two months of 2024, nearly matching the number recorded in the entire previous year.

And recently, antibiotic-resistant strains of Bordetella pertussis have been discovered.

Dr Loo said at this stage it was too early to tell which strain was causing the outbreak in Australia.

Research conducted in collaboration with UNSW in 2020 It was found that a new strain emerged in the country during the 2008 outbreak, which may have led to an increase in the number of infections.

The “smarter” strain could be targeted by only two of the vaccine's components, meaning the disease is likely to survive whether a person is vaccinated or not.

“In Australia we use a three-component vaccine that targets three proteins on the bacteria,” Dr Loo said.

“Five-component vaccines exist but are not widely used in Australia. We hope that the additional component will allow us to target these strains more effectively.”

Prof Richmond said several new whooping cough vaccines were being trialled which may provide longer-lasting immunity and block infection.

He's working with the Telethon Kids Institute to develop a nasal spray to prevent bacterial infections in the first place.

“Current vaccines aim to stop the progression of the disease rather than eliminate infection,” he said.

“It's likely that within the next few years there will be many vaccines available that are better than the ones we have today.”

Is it time for a booster shot?

Dr Lu and Professor Richmond stressed that the current vaccines remain effective and remain the best way to maintain protection.