How climate change could expose new epidemics

A healthcare worker uses a swab to collect a sample at a temporary testing centre for the novel coronavirus in Madrid on August 17, 2020. – Just seven weeks after bringing its first coronavirus wave under control, experts say Spain is once again in a “critical” situation with the worst infection rate in Western Europe. (Photo by OSCAR DEL POZO / AFP)

by Amélie BOTTOLLIER-DEPOIS
Agence France Presse

PARIS, France (AFP) — Long-dormant viruses brought back to life; the resurgence of deadly and disfiguring smallpox; a dengue or zika “season” in Europe.

These could be disaster movie storylines, but they are also serious and increasingly plausible scenarios of epidemics unleashed by global warming, scientists say.

The COVID-19 pandemic that has swept the globe and claimed over 760,000 lives so far almost certainly came from a wild bat, highlighting the danger of humanity’s constant encroachment on the planet’s dwindling wild spaces.

But the expanding ecological footprint of our species could trigger epidemics in other ways too.

People wearing face masks are seen next to the cage of a Siberian tiger at the Wuhan Zoo in Wuhan, in China’s central Hubei province on May 24, 2020. – China is “open” to international cooperation to identify the source of the novel coronavirus, but any investigation must be led by the World Health Organization and “free of political interference”, China’s foreign minister said on May 24. (Photo by Hector RETAMAL / AFP)

Climate change — already wreaking havoc with one degree Celsius of warming — is also emerging as a driver of infectious disease, whether by expanding the footprint of malaria- and dengue-carrying mosquitos, or defrosting prehistoric pathogens from the Siberian permafrost.

– ‘Ignorance is our enemy’ –
“In my darkest moments, I see a really horrible future for Homo sapiens because we are an animal, and when we extend our borders things will happen to us,” said Birgitta Evengard, a researcher in clinical microbiology at Umea University in Sweden.

“Our biggest enemy is our own ignorance,” she added. “Nature is full of microorganisms.”

A veterinary worker carries a sack with dead ducks at a small farm affected by avian flu virus in the Siberian village of Oktyabrskoe in the Ural mountain region of Chelyabinsk 22 August 2005. . AFP PHOTO / YURI TUTOV (Photo by Yuri Tutov / AFP)

Think of permafrost, a climate change time bomb spread across Russia, Canada and Alaska that contains three times the carbon that has been emitted since the start of industrialisation.

Even if humanity manages to cap global warming at under two degrees Celsius, the cornerstone goal of the 2015 Paris Agreement, the permafrost area will decrease by a quarter by 2100, according to the UN’s climate science panel, the IPCC.

And then there are the permafrost’s hidden treasures.

“Microorganisms can survive in frozen space for a long, long time,” said Vladimir Romanovsky, a professor of geophysics at the University of Alaska in Fairbanks.

– An Anthrax comeback? –
As ground thaws, once-frozen soil particles, organic material and microorganisms that had been locked away for millennia are carried toward the surface by water flows, he explained.

“That’s how thawing can spread these microorganisms into present day environments.”

There are already examples of ancient, long-frozen bugs coming to life.

“When you put a seed into soil that is then frozen for thousands of years, nothing happens,” said Jean-Michel Claverie, an emeritus professor of genomics at the School of Medicine of Aix-Marseille University in France.

“But when you warm the earth, the seed will be able to germinate,” he added. “That is similar to what happens with a virus.”

Claverie’s lab has successfully revived Siberian viruses that are at least 30,000 years old.

These reanimated bugs only attack amoebas, but tens of thousands of years ago there were certainly others that aimed higher up the food chain.

This photo taken on August 8, 2020, from the Gornergrat, 3’089 meter hight above the resort of Zermatt shows a melting part of the Gornergletscher glacier. (Photo by Fabrice COFFRINI / AFP)

“Neanderthals, mammoths, woolly rhinos all got sick, and many died,” said Claverie. “Some of the viruses that caused their sicknesses are probably still in the soil.”

The number of bacteria and viruses lurking in the permafrost is incalculable, but the more important question is how dangerous they are.

And here, scientists disagree.

“Anthrax shows that bacteria can be resting in permafrost for hundreds of years and be revived,” said Evengard.

In 2016, a child in Siberia died from the disease, which had disappeared from the region at least 75 years earlier.

– Two-million-year-old pathogens –
This case has been attributed to the thawing of a long-buried carcass, but some experts counter that the animal remains in question may have been in shallow dirt and thus subject to periodic thawing.

Other pathogens — such as smallpox or the influenza strain that killed tens of millions in 1917 and 1918 — may also be present in the sub-Arctic region.

(File photo) A screen shows an old picture of victims of the Spanish Flu, in the Health Organisation (WHO) Executive board room, on the second day of a three-day global bird flu conference, at the WHO headquarters, in Geneva, 08 November 2005. AFP PHOTO FABRICE COFFRINI (Photo by FABRICE COFFRINI / AFP)

But they “have probably been inactivated”, Romanovsky concluded in a study published earlier this year.

For Claverie, however, the return of smallpox — officially declared eradicated 50 years ago — cannot be excluded. 18th- and 19th-century victims of the disease “buried in cemetaries in Siberia are totally preserved by the cold,” he noted.

In the unlikely event of a local epidemic, a vaccine is available.

The real danger, he added, lies in deeper strata where unknown pathogens that have not seen daylight for two million years or more may be exposed by global warming.

If there were no hosts for the bugs to infect there would not be a problem, but climate change — indirectly — has intervened here as well.

“With the industrial exploitation of the Arctic, all the risk factors are there — pathogens and the people to carry them,” Claverie said.

The revival of ancient bacteria or viruses remains speculative, but climate change has already boosted the spread of diseases that kill about half a million people every year: malaria, dengue, chikungunya, zika.

(FILES) This undated file handout image obtained July 15, 2020, courtesy of National Institute of Allergy and Infectious Diseases(NIH/NIAID), shows a transmission electron micrograph of SARS-CoV-2 virus particles, isolated from a patient, captured and color-enhanced at the NIAID Integrated Research Facility (IRF) in Fort Detrick, Maryland. – The US has begun late stage clinical trials into a drug formulated to fight COVID-19, officials said on August 4, 2020. The medicine is an antibody against the new coronavirus called LY-CoV555, which was identified in the blood sample of a recovered patient by Canada’s Abcellera Biologics. It was then developed synthetically for mass production by US-based Lilly Research Laboratories in partnership with Abcellera. (Photo by Handout / National Institute of Allergy and Infectious Diseases / AFP)

“Mosquitoes moving their range north are now able to overwinter in some temperate regions,” said Jeanne Fair, deputy group leader for biosecurity and public health at the Los Alamos National Laboratory in New Mexico.

“They also have longer breeding periods.”

– ‘Climate change aperitif’ –
Native to southeast Asia, the tiger mosquito (Aedes albopictus) — which carries dengue and chikungunya — arrived in southern Europe in the first decade of this century and has been moving rapidly north ever since, to Paris and beyond.

Meanwhile, another dengue-bearing mosquito, Aedes aegypti, has also appeared in Europe. Whichever species may be the culprit, the Europe Centre for Disease Prevention and Control (ECDC) has registered 40 cases of local transmission of dengue between 2010 and 2019.

A municipal employee takes part in a fumigation operation against Aedes aegypti mosquito –the mosquito that can spread dengue fever– in San Jose, on July 2, 2020. (Photo by Ezequiel BECERRA / AFP) /

“An increase in mean temperature could result in seasonal dengue transmission in southern Europe if A. aegypti infected with virus were to be established,” according to the Europe Centre for Disease Prevention and Control.

As for malaria — a disease that once blighted southern Europe and the southern United States and for which an effective treatment exists — the risk of exposure depends in large part on social-economic conditions.

More than five billion people could be living in malaria-affected regions by 2050 if climate change continues unabated, but strong economic growth and social development could reduce that number to less than two billion, according to a study cited by the IPCC.

“Recent experience in southern Europe demonstrates how rapidly the disease may reappear if health services falter,” the IPCC said in 2013, alluding to a resurgence of cases in Greece in 2008.

In Africa — which saw 228 million cases of malaria in 2018, 94 percent of the world’s total — the disease vector is moving into new regions, notably the high-altitude plains of Ethiopia and Kenya.

For the moment, the signals for communicable tropical diseases “are worrying in terms of expanding vectors, not necessarily transmission,” said Cyril Caminade, an epidemiologist working on climate change at the Institute of Infection and Global Health at the University of Liverpool.

“That said, we’re only tasting the aperitif of climate change so far,” he added.

 

© Agence France-Presse

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