August 13, 2022

Could social distancing make the flu extinct?

It was the first time the Sapanawa tribe had ever made contact.

The meeting occurred in the remote Serra do Divisor National Park – a vast area of the Amazon basin in the far west of Brazil. From the sky, it looks like a uniform stretch of unbroken forest; concealed beneath are waterfalls, rivers, dormant volcanos and human villages. This is a place where giant armadillos, tapirs and jaguars roam the landscape, and uncontacted peoples live largely as they have done for some 32,000 years. 

But for one isolated tribe, everything changed in 2014. Several members of the Sapanawa strayed out of their time warp after fleeing violent attacks from logging gangs across the border in Peru. They raided the village of another remote tribe, who had settled down and made contact with modern civilisation decades ago. Afterwards, they spent three weeks in the company of FUNAI, a government body that protects indigenous people from the outside world.

Indigenous Amazonians are anomalies in almost every way – they speak ancient, little-known languages, some of which lack words for numbers and even colours. Their societies are often egalitarian. And they are also among the only communities on Earth not to suffer from the diseases which plague the rest of humanity. Some uncontacted peoples – though not all – have never experienced the misery of having a cold or the flu, or other more life-threatening illnesses such as measles.

For the Sapanawa, this fragile disease-free state ended remarkably quickly after their first contact. Within days, many became gravely unwell; they had caught a respiratory infection, probably influenza. When tribes are first exposed to the flu, the fatality rate is usually extremely high. But on this occasion, there was a happy ending. The raiders received medical treatment and no one died, so after a brief period of quarantine, they returned home to their people. As far as anyone knows, this was the end of that flu epidemic.

The presence of flu-free societies raises an important question: could the rest of the world ever be rid of this virus? As it happens, the world is making some tantalising first steps towards this goal.

Back in January 2020, at the end of the Australian summer, the country had 6,962 cases of the flu confirmed via a laboratory test. At this time, Covid-19 was still known only as “the novel coronavirus” and mostly confined to China. Ordinarily, you would have expected to see more and more cases of the flu as the days became shorter and winter descended.

Instead, something unexpected happened. By April there were just 229 cases of the flu – down from 18,705 at the same time the previous year. Covid-19 had already ripped across the world, collectively infecting more than a million people, including the British prime minister, and spreading to every continent except Antarctica. Lockdowns had been imposed, hand-washing had been popularised and mask-wearing had become commonplace – though the latter was still much more widely practiced in Asia than elsewhere.

By August, it was clear that Australia’s flu season had been the mildest on record. In all, there were fewer than a 10th of the infections seen in 2019 – and the vast majority of these occurred before the pandemic hit. This is all against a backdrop of more testing than had ever been conducted before.

The same pattern also occurred elsewhere. The co-head of South Africa’s National Institute of Communicable Diseases (NICD) recently told CBS News that the country “just didn’t have a flu season this year”, while in New Zealand, doctors didn’t detect a single flu case during their annual screening drive, though last year 57% of the swabs they took were positive. 

Now winter is over in the Southern Hemisphere and beginning in the North. And though it’s still early in the season, already things look radically different to how they ordinarily would.

As of September, the World Health Organization (WHO) reported the missing flu cases were a global phenomenon, with significantly lower levels than would be expected, from tropical Africa to the Caribbean. For the week beginning 7 September, the flu tracker FluMart recorded just 12 lab-confirmed cases of the flu on the entire planet.   

“What we’re seeing in Australia, New Zealand, South America, Hong Kong, are really, really attenuated seasons of not just the flu, but also respiratory syncytial virus (RSV),” says Sarah Cobey, an epidemiologist at the University of Chicago. 

Of course, there are many possible reasons that cases might be down this year. People could be afraid to seek medical treatment, and in some places, there it’s possible that fewer tests were conducted as resources were diverted elsewhere. But many experts suspect that the trend is down to physical distancing and improvements to hygiene in the wake of the pandemic.