Post-pandemic birthrate breaks from flu trend
The birthrate in New Zealand plummeted after the deadly influenza pandemic a hundred years ago, but the trend has yet to show up in Covid-19’s wake.
In 2019 University of Otago epidemiologist Professor Nick Wilson co-authored an article published in the New Zealand Medical Journal (NZMJ) with professors Nikki Turner and Michael Baker on the birth reduction ‘‘shock’’ that followed the flu pandemic.
Wilson said the difference between now and then was that the pandemic was an entirely different beast to that of 100 years ago.
Then births fell through a range of different factors, such as high death rates in young people in their 20s, Wilson said.
The peak age of death was about 27, he said – ‘‘so there were women who were around their peak time for getting pregnant actually dying in large numbers’’.
Flu infection in pregnant women caused miscarriages and stillbirths, and the whole situation was ‘‘complicated by many thousands of men who were still overseas and coming back from World War I’’.
Figures from the Ministry of Health show 58,445 live births in 2020 – close to 2018’s total of 58,463.
In 1919, there were 3,756 fewer non-Māori and 239 fewer Māori births than the pre-pandemic year of 1917, equating to a reduction of birth rates per 1,000 population of 16.6% and 19.8% respectively.
Wilson said at that time, there was ‘‘a lot of infection happening’’, while in New Zealand in 2019 and 2020, there was very little infection from Covid-19, and the country had only just seen mass infections this year.
‘‘It involved a lot of deaths, around 9000 in the whole country, and a lot of them were amongst 20-year-olds and 30-year-olds, and probably half the population in New Zealand was infected, all in those very brief few months.’’
Wilson theorised in his paper that aside from the deaths of young women, and those of embryos and foetuses, reduced sexual activity was a factor too.
The peak pandemic months of November and December in 1918 caused significant social disruption.
‘‘People were just possibly having less sexual activity, because they were separated,’’ Wilson said.
‘‘If you have thousands of people dying around the country, or getting sick, people will move from one city to another to look after their sick relative, and so on. And the general tragedy of having lots of relatives dying ... would have been a bit of a downer for normal activities.’’
The article also theorised that estimates of natality losses were actually underestimates, because men returning from war in late 1918 and 1919 brought an estimated 3,000 wives from England with them, some of whom would have been pregnant.
The adult male population also would have been greater in late 1918 and 1919 than in 1917 as men returned from combat.
In the NZMJ article, the natality loss was found to be relatively higher for Māori. The authors wrote that pandemic planning needed to consider ‘‘ ways to prevent such future burdens and associated inequities’’.
Asked if he knew what was just around the corner, in terms of the pandemic, Wilson said he did because he’d been writing about pandemics for 10 years and warning that New Zealand needed to be better prepared.
‘‘But no-one in the Ministry of Health listened. We published articles in 2019 and in 2017 on the need for improved border control. In public health, you’re used to not being listened to. So it wasn’t a great surprise.’’
Epidemiologists knew that every century there was going to be several big flu pandemics – ‘‘so that’s why we bother researching these things’’.
Wilson said the Ministry of Health didn’t mention coronaviruses in its pandemic plan, which was ‘‘pretty crazy’’ since we had had SARS in 2003.
Few countries were properly prepared, he said, apart from Asian countries that had had a bad experience with SARS.
‘‘They were the best prepared. New Zealand had quite a lot of a ‘She’ll be right attitude’, I think.’’
The risk of pandemics in the future, he said, was rising because of the ongoing intrusion of humans into wildlife areas.
Issues like the mixing of pigs and poultry were not being addressed adequately.
‘‘There are still lots of wet markets throughout Asia, where all these different animals are stacked on top of each other and they exchange their viruses. From an epidemiological point of view, wet markets are just insane.’’
Wilson said we should be telling everyone and every Asian government, to clean up their acts, and help them do it, as it was ‘‘in our interest’’.
The good news about future pandemics was that we had tools, and we could come up with better vaccines in the future, though things were just ‘‘moving too slowly,’’ he said.
‘‘The world has been shocked by the trillions of dollars that Covid has cost.
‘‘So hopefully, governments will start spending on better pandemic plans, better vaccine development [and] better surveillance. Pandemics can be identified early and can be prevented.’’