Health techniques throughout the southern hemisphere had been bracing a number of months in the past for his or her annual surge in influenza cases, which alongside Covid-19 may have overwhelmed hospitals. They by no means got here.

Many nations within the southern half of the globe have as an alternative skilled both record low ranges of flu or none in any respect, public well being specialists in Australia, New Zealand and South America have mentioned, sparing probably tens of hundreds of lives and providing a glimmer of hope as winter approaches within the northern hemisphere.

General practitioners in New Zealand haven’t detected a single influenza case since they began screening sufferers in June, well being knowledge exhibits; final 12 months about 57% of the samples they collected had been optimistic.

The final flu cases detected by main hospitals in Auckland, the nation’s largest metropolis, had been in April. “It’s amazing. There’s just nothing there at all. No influenza,” mentioned Michael Baker, professor of public well being on the University of Otago in Wellington.

New Zealand’s Covid-19 rates are among the many lowest on this planet, however even however the pandemic, folks within the nation have skilled their healthiest chilly months on record. “Our excess winter mortality peak has largely disappeared,” Baker mentioned.

A monitoring system that displays a cohort of a minimum of 30,000 folks for influenza-like signs exhibits as few as 0.3% of New Zealanders reported coughs or fevers some weeks throughout their winter, a tenfold lower on some earlier years.

The development holds true throughout the Tasman Sea in Australia, the place Covid-19 restrictions have additionally deeply dented charges of flu and different respiratory sicknesses. The nation recorded greater than 131,000 influenza cases within the peak months of July and August final 12 months, in keeping with authorities knowledge. Over the identical interval this 12 months, there have been 315.

“Cases have fallen off a cliff since March,” mentioned Prof Ian Barr, deputy director of the World Health Organization’s collaborating centre for reference and analysis on influenza, in Melbourne.

Fewer than 40 Australians have died from influenza this 12 months, in comparison with greater than 950 final 12 months, “and there haven’t been any deaths for the past three to four months”, Barr added.

Even throughout South America and in South Africa, the place lockdowns have been patchy or more durable to implement, and Covid-19 has unfold broadly and killed tens of hundreds of individuals, flu charges have been effectively beneath historic charges or nonexistent – regardless of elevated testing for it within the Americas, in keeping with the Pan American Health Organisation.

This obvious contradiction – Sars-CoV-2 rising exponentially whereas influenza nearly disappears – illustrates a key distinction between the 2 viruses. The seasonal flu is not only much less lethal, however considerably much less virulent, Baker mentioned.

Populations have increased immunity to seasonal influenza, whether or not acquired naturally or via vaccines, whereas journey bans instituted from March interrupted the traditional migration of the virus from the northern hemisphere to the south.

As an unprecedented reside experiment on a large inhabitants, it may supply some excellent news for northern hemisphere nations heading into their very own flu season, simply as drier air and extra time indoors are anticipated to drive up Covid-19 charges. Even comparatively much less stringent quarantines seem like surprisingly potent at suppressing influenza and different widespread respiratory sicknesses.

“You would still see a flu season, but I expect it would be much less intense,” Baker mentioned. “Northern hemisphere countries that are actively suppressing Covid-19 to some degree should get a lot of protection [from influenza] by doing that.”

It may imply that extra individuals are vulnerable to flu strains within the years forward, having not acquired any type of immunity this 12 months, Barr mentioned, although he added the risk would considerably lower if folks saved washing their palms completely and wore masks in crowded areas even after the pandemic subsides.

In a 12 months that will likely be studied by public well being specialists for many years, it additionally factors to new methods of preventing the long run influenza pandemics that some scientists regard as inevitable.

“[Before,] it was thought that when a new influenza pandemic virus arrives, all you can do is dampen it down, you can’t stop it,” he mentioned. “We now know that if you had a pandemic flu virus of sufficient severity, you could take the elimination approach, or even the exclusion approach, as Taiwan has done with Covid-19.”

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