If the future is destined to track a new, COVID-19 study out of China, Alaskans might want to start hoping for a warm, wet summer.
In a study published today on medRxiv, they report that when climate conditions are compared to 578 datasets documenting COVID-19 eruptions in China, Europe, the U.S. and other countries, temperature and precipitation show “distinct impacts on early and late transmission of COVID-19 in the world after excluding the confounding factors. The early transmission ability of COVID-19 peaked around 6.3°C (43 degrees) without or with little human intervention.”
MedRxiv studies are preliminary and have not gone through peer review, a sometimes exhaustive process in which independent scientists are recruited to challenge the conclusions of their colleagues. But the scientists who completed the study are respected members of the Chinese Academy of Sciences.
They reported their latest work was motivated by an “extensive review by the National Academy of Sciences, Engineering and Medicine of the United States of America indicated that conclusions on associations between climate and COVID-19 were elusive with high uncertainty due to significant caveats in most previous studies such as limitation in time and space, data quality and confounding factors. Therefore, it is necessary to reveal the impacts of climate factors on the spread of COVID-19 by using a more extensive global dataset covering a large geographic and climatic variation, and by
excluding the impacts of human factors” such as national and community lockdowns and quarantines.
Once that is done, the researchers claim, the data clearly shows a climate effect on SARS-CoV-2 as has proven to be the case with many other viruses “such as influenza epidemics, human coronaviruses (HCoVK29E, HCoV-HKU1, HCoV-NL63, and HCoV-OC43), and the SARS(-CoV-1) coronavirus.
“We found that both human and climate factors affected the spread of COVID-19, but temperature showed distinct impacts on the early and late spread of COVID-19.”
The study does not suggest SARS-CoV-2 disappears at an average temperature of 43 degrees, but it says that as temperatures increase above that level the virus becomes less and less successful at jumping from human to human as long as humidity levels are adequate.
“We found precipitation showed a significant and negative association with the average daily increase rate (𝑟𝑖) in China, suggesting a wet climate might decrease the transmission ability of COVID-19, which is consistent with a previous study,” they wrote.
Summarizing earlier research, they wrote that “(M.) Triplett found a downward trend of COVID-19 cases with a maximum temperature above 22.5°C (72.5 degrees). (J.) Wang et al reported that high temperature and high humidity significantly reduced the effective reproduction number of COVID-19 in China. (H.) Qi et al reported the negative association between incidence of COVID-19 and temperature or relative humidity in China.”
The average June temperature in the Anchorage Metro area, home to more than half the state’s population, is 56 degrees with an average high of 63 degrees. But the urban core of Alaska saw record temperatures last summer with 46 days over 70 degrees in Anchorage, and another warm summer is forecast by the National Weather Service’s Climate Prediction Center.
The conclusions in the latest study appear buttressed by the global status of COVID-19 cases today.
“Using niche models, tropical climates are less vulnerable than temperate climates,” the authors wrote. Worldometers COVID-19 tracker generally shows tropical nations with cases in the hundreds while nations in temperate climates report cases in the thousands or tens of thousands.
About three of every 10 people infected around the globe are Americans. Almost 60 percent of them live in a handful of states in the Northeast. On a per-capita, nation-by-nation level, hard-hit Spain remains the world leader in infections with 5,950 per million people, according to that website, and deaths with 593 per million.
The Chinese researchers noted that in tracking COVID-19 outbreaks they found strong associations with large population centers and “the founding population size of early reported cases.”
The first case in New York City appeared to arrive from Iran, but the nation’s by far largest metropolis daily welcomes travelers from everywhere. With a population of nearly 19.5 million people, it is home to almost twice as many people as Sweden, 10.1 million and nearly three times as many as Norway, 5.4 million.
Living in a city with a vertically stacked population larger than all but 10 European nations, New York Post reporter Tamar Lapin aptly described her hometown as the perfect setting for “a case study in how the illness can spread at lightning speed in a packed, high-traffic, petri-dish environment.”
With a statewide population less than a 25th that of NYC, Alaska could be described as the near polar opposite of the Big Apple. Its low density coupled with state-ordered social distancing and isolation of infected patients – moves well documented as helpful in slowing the spread of infectious diseases – could account for the state having come through the pandemic with minimal casualties to date.
As of this writing, the state has seen only 399 cases, according to the Department of Health and Social Services. Three-hundred-forty-five of the 399 infected (86 percent) are reported to have already recovered. Ten have died.
The death rate at his point lags far behind that for flu/pneumonia which on average kills 69 Alaskans per year, and it is a fraction the number of annual deaths from suicide (184) or accidents (397), according to the state Division of Public Health.
Cancer and heart disease remain the big killers in Alaska as they have been for years. But COVID-19 is unlikely to have stopped killing in Alaska. There are even suggestions it might have been slowed in places such as Alaska where weather sometimes naturally distances people without need for government action.
Noting the unavoidable interaction between human-control efforts and climate, the scientists observed that “results indicated that cold and wet climate decreased the control efficiency on COVID-19. This is likely because cold and wet conditions did not favor human movement outside, thus the lockdown and social distancing measures may have worked better in warm and dry conditions rather than in cold and dry conditions.”
How the May-June rush of Alaskans to get out and socialize under the midnight sun might alter the COVID-19 situation now that the Alaska lockdown is being lifted is thus an unknown. The study also concluded that it appears possible to land a knock-out blow to the pathogen if it is caught early and the infected are quickly isolated so as to prevent the disease from establishing a foothold.
“The spread of disease is very similar to the biological invasion defined by the Allee effect,” they wrote. “The Allee effect suggested that founding population size was essential for the successful establishment of alien species. It has been widely supported in studies of biological invasions, as well as by our observations.”
New Zealand believed it had wiped out the founding population of SARS-CoV-2 in that country after a month-long shutdown that closed its borders and limited Kiwis to contact with household members only.
“How New Zealand’s ‘eliminate’ strategy brought new coronavirus cases down to zero,” CNBC headlined on May 5. The country was then heralding its first day with no new cases.
Ten cases have popped up since. Three involved people flying in from elsewhere, but the other seven appear to be community spread. Everywhere around the global SARS-CoV-2 is proving pervasive. Some scientists have suggested that although the disease might be minimized the world could be dealing with it for a long time much as it does with flu.
While Alaska is in its spring season heading into summer, New Zeland is in fall heading into winter. The Chinese have warned that might alter outcomes going forward.
“The summer season would decrease the late transmission ability of the northern hemisphere but increase that of the southern hemisphere,” they wrote. Their analysis also suggests that while summer might bring temperatures that offer the 49th state’s population centers some protection from the pandemic, the story could be different north of the Arctic Circle.
“Summer seasons would decrease the early transmission risk of COVID-19 in low-latitude or low-altitude regions, but increase the transmission risk in the high-latitude or high-altitude regions,” they concluded.
Almost no one lives at high altitude in Alaska, but there are a number of communities situated north of the Arctic Circle.