Earlier this month, the number of whooping cough cases recorded for 2024 passed Australia’s all-time high for a calendar year. The number of cases is already eight times higher than it was in all of 2023.
“Australia is currently in the midst of a whooping cough epidemic,” said Professor Nicholas Wood of University of Sydney.
Whooping cough is a respiratory infection caused by the pertussis bacteria. It is most dangerous for infants when they are just a few months old.
As with flu and many other respiratory infections, whooping cough practically disappeared with the social distancing restrictions implemented in 2020 and 2021. There were just 482 cases in all of 2022 compared to over 41,000 so far in 2024.
One positive aspect is that so far the outbreak has been mostly confined to the eastern states. Almost half of all cases have occurred in New South Wales, while a further 28% of the national total have been reported in Queensland and the great majority of the rest in Victoria.
Similar spikes in whooping cough cases have been seen worldwide. The Netherlands has reported over 20,000 cases this calendar year. France is going through its worst outbreak in 25 years.
The figures are lower in the Western hemisphere, although still notably high compared to recent years, with 25,000 causes reported in the US in 2024 so far. The Pan-American Health Organization also issued an alert in July.
Some have sought to explain the situation by reference to declining vaccination rates after COVID. However, whooping cough vaccination rates have scarcely declined, only a percentage point or two depending on which state you live in compared with 2019.
Of course vaccination remains the best strategy. As Dr Tim Jones of the Australian College of General Practitioners said, “It’s very important to be promoting boosters at the moment as an incredibly effective prevention strategy for this condition.”
However, according to a French study, new genetic developments in the post-pandemic strains of whooping cough are part of explanation for the sudden rise in cases. Researchers found previously rare antigens in pertussis are now common. They also noted the more obvious explanation that lower exposure to pertussis has caused population immunity to gradually wane in the past few years.
Although still relatively rare at the population level, it is one to watch for parents. It is estimated that over half of infants diagnosed with whooping cough will require hospital admission.
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