What infection rates in Iceland and Australia may reveal about how COVID-19 could spread in the US
Research into the possible effects of heat, humidity and population density on the transmission of the new coronavirus (SARS-CoV-2) has led to the theory that warmer weather during spring and summer in the Northern Hemisphere may lead to a decline in the rate of spread of COVID-19, the illness it causes, but there is a range of opinions on the matter in the infectious disease community.
The effect of the sun’s ultraviolet rays may play a larger role than even heat and humidity. As the latest data is analyzed regarding the possible role that weather and climate factors may play in the rate of spread of COVID-19 continues, it may provide some new clues for what to expect in the United States as summer approaches. In particular, a look at the per capita infection rates of Iceland and Australia might possibly offer a glimpse at UV’s possible impact on the spread of COVID-19 around the world.
As of Tuesday, Iceland has among the world's highest rates of confirmed coronavirus cases per capita at 0.177 percent, with 648 cases from a population of 364,260. Australia’s confirmed infected rate is just 0.0083 percent – 2,044 cases from a population of 25.4 million people.
That means Iceland’s infection rate is roughly 22 times greater than Australia’s, not factoring in other variables for either location. While heat and humidity could play a role in the disparity, a look at the impact of UV rays reveals it may be more substantial than the other two weather factors.
The average temperature in Sydney, Australia, was 74.8 F from Jan. 1, 2020, until March 15, which was the summer season in the Southern Hemisphere. It was 32.1 F in Reykjavik, Iceland, during the same time period, which was winter in the Northern Hemisphere.
For a closer comparison, AccuWeather looked at a city also experiencing winter at that time. Iceland’s average temperature was comparable to Chicago’s for the same time period (32.6 F). But Chicago’s coronavirus cases per capita were substantially lower, with Iceland's rate soaring almost 10 times higher than Chicago’s rate (0.0178 percent, based on 490 cases among a population of 2.74 million).
The role sunlight plays in destroying viruses has already been noted by John Nicholls, a pathology professor at the University of Hong Kong who is part of a team studying a laboratory-grown copy of SARS-CoV-2. When contacted by AccuWeather this week, he said his team is investigating whether sunlight affects the virus causing COVID-19 the way it affects other viruses, like the flu.
“As previously published works show that influenza can be inactivated by simulated sunlight, we are exploring the experimental setting to see if there can be similar inactivation of SARS-CoV-2 by sunlight,” Nicholls told AccuWeather.
Because Iceland is so far north -- its latitude is 64.1 and its mainland is only a few degrees south of the Arctic Circle -- the country receives fewer hours of sun and less solar intensity than cities farther south. The map below shows the Dec.-Jan.-Feb average for ultraviolet light, showing Iceland’s sun deficit compared to Chicago, with a latitude of 41.8, and especially Sydney (33.8).
Source: "KNMI/ESA; http://www.temis.nl/"
"Iceland gets almost no ultraviolet radiation during the winter," said AccuWeather Meteorologist Jesse Ferrell. "Chicago does, so it's better off – and Sydney is much higher on the scale than either of them.”
The good news for Iceland is that it will continue to experience more UV as spring continues into summer, which could possibly impact its number of coronavirus cases.
Reykjavik, Iceland, for example, had a maximum sun angle of just 2.54 degrees at the winter solstice on Dec. 21, 2019. That angle will increase to 52.4 degrees by the arrival of the summer solstice on June 20, 2020. "That means a greater amount of solar radiation reaches the ground,” said AccuWeather Senior Meteorologist Dave Samuhel.
“The variability of sunshine from December to June is roughly 25 to 1,” said AccuWeather Founder and CEO Dr. Joel N. Myers. “I suspect if there’s anything to these numbers regarding the possible impact of UV on COVID-19, then comparing Australia to Iceland shows the effect of the ultraviolet radiation. And in the Northern Hemisphere, the ultraviolet waves from the sun are increasing dramatically day by day as we go through spring.”
The increased solar activity for Iceland, of course, means fall and winter will soon occur for Southern Hemisphere locations such as Australia, which could lead to an increase in coronavirus cases there.
Until there's scientific data, we may never know given all of the extreme public health measures that are in place and undoubtedly slowing the spread. The analysis of UV’s role does not rule out other factors that may be affecting the COVID-19 per capita rates.
An elderly lady walks across the usually busy Columbus Drive that splits Chicago's Grant Park in half, on the first work day since Illinois Gov. J.B. Pritzker gave a shelter-in-place order last week, Monday, March 23, 2020, photo, in Chicago. (AP Photo/Charles Rex Arbogast)
Iceland’s “case detection is probably the most complete of any country on the planet, which may explain the high per capita cases,” Dr. Bryan Lewis, a professor at the Biocomplexity Institute, told AccuWeather.
“The difference between Iceland and Chicago may be more about the travel restrictions, just physical placement in the world and ‘good luck,’ Lewis added. “Infections in the U.S. are ramping up and it will be a while, but we may well have more infections per capita than Iceland at some point.”
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