PLAGUE JOURNAL May 2020: Temperature & Skies, Part 2
Climate: a clue from the love doctor, Italy gets hit early, spreads north.
[Note: All Plague Journal entries were written as events unfolded. I have edited the drafts for clarity, but the tone and content are original, reflecting what we could see at the time.]
A Clue from the Love Doctor
On May 9th, 2020 I happened to be listening to a podcast that included Dr. Drew Pinsky, formerly of the old Loveline radio program, who said that flu viruses transmit most successfully at around 40 degrees, that above or below 40 degrees they struggle to spread. Why had I never heard that before? We were three months in. It’s possible that this simple information appeared somewhere in the millions of pages of the Times or the New Yorker or the Atlantic or the thousands of hours of television, but if it did, it didn’t break through the noise. Neither I nor anyone I asked among my friends had heard such a thing, but apparently it’s common knowledge to a physician like Pinsky. I was familiar with the term “flu season” but I associated it with winter generally, not with a specific temperature, and anyway we were told sternly by the press that the coronavirus was nothing like the flu, even though the CDC states that they are “both contagious respiratory illnesses” and lists nine symptoms they share in common and just one they don’t (“change in or loss of taste or smell”).
I went back and looked at the disparities in the North Atlantic: Greenland had zero deaths, Iceland had 29 deaths per million, and Ireland had 303 deaths per million as of mid-May. Average early March temperatures in Nuuk, Greenland range from just 12 to 19 degrees Fahrenheit; in Reykjavík, from 29 to 37; in Dublin, from 38 to 48. The pattern suggested that for the coronavirus to spread rapidly, lows have to be above freezing—but not by much. As lows begin to climb above forty, the spread slows significantly, especially as they clear 55 or so. The warmer the weather, the slower the spread and the fewer the cases. In hot weather—especially hot sunny weather—there is virtually no spreading at all.
[Update, 2021: by summer, we saw that places with widespread air-conditioning and intense heat in saw spreading, though fatalities were lower than in cool weather. Warm sunny areas without air-conditioning continued to see minimal spreading as I noted in May 2020.]
Meat Plants
I thought about the Upper Midwest of the U.S., which was so lightly hit early. Temperatures in Minneapolis range from 20 to 35 degrees on March 1st but rise to 32 to 50 by the end of March. In late April and early May we began getting the news about spreading in meat-processing plants. When I mentioned Dr. Drew’s comments to a friend who owns restaurants, he said that plants are kept at or just below 40 degrees. I had wondered why these plants were so much harder hit than other places requiring close work among employees. Nursing homes and meat-processing plants were hit while other factories, distribution centers, grocery stores, liquor stores, gas stations, and a hundred other kinds of workplaces were spared. We knew that people in meat plants work in close quarters and need to shout to be heard over the equipment, and we knew that they often lived with many other family members in close quarters, but these things are true for thousands of manufacturing and distribution centers. Working in a 39-degree environment at the time of year when outdoor temperatures are in the 30s puts you at the highest risk.
There are meat processing plants all over the country, including Texas, California, Florida, Alabama, Georgia, and North Carolina, yet the early headlines were about the plants in Minnesota, the Dakotas, Nebraska, Kansas, and northern Colorado (which isn’t to say people haven’t gotten sick in warmer states, only that it seemed considerably worse in the north). Could it be that in warmer and sunnier climates, where people went outside at lunch, during a break, or on weekends, they were more protected against infection and illness? Could it be that sunshine protected against the coronavirus?
Italy Gets Hit Early in the South but Spreads North
Italy was hit early, before the U.S. and the rest of Europe, and I’d heard that northern was hardest hit. Turin, Italy’s fourth-largest city, and Milan, the second-largest, are both in the north and have identical March 1st average temperatures of 36 to 53. Although they were hit hard, they weren’t hit first. The first cases were reported in Rome on January 31st, in two Chinese tourists. The day before, January 30th, Rome’s temperature ranged from 38 to 55, the only day that week that fell below 40. If the tourists were already in town, conditions would have been ideal to make them highly infectious. In February, Rome’s temperatures fell to 40 or below on half of the days but never fell below freezing—spreader weather.
There was an outbreak of 16 cases in Lombardy to the north on the 21st of February. I would learn, shortly after I began looking up temperatures, that the typical incubation period of the coronavirus is 5 to 6 days, which means that the Lombardy infections would likely have occurred on or near February 15th and 16th. Milan is the capital of Lombardy. Milan’s lows on the 15th and 16th were 32 degrees both days and had been between 30 and 40 for nine days in a row.
By early March, the virus was in all regions of Italy. As time went on, the north would take the biggest hit. In February of 2020, Rome’s average daily low was 42.5 to 60, while Milan’s was 37.4 to 56 and Turin’s was 35.7 to 57.3. Rome’s average lows are already climbing above 40 by March, and the highs begin clearing 60 by mid-March. Most of Italy is overcast in the winter, cloudy roughly 50% of the time. Rome begins to clear slightly in the spring, while Milan and Turin get cloudier. (The classic wine grape of Piedmont, just south of Turin, is nebbiolo, which means “fog” in Italian.)
Infections spread quickly in Lombardy, which would have by far the highest infection rates in Italy. [UPDATE: A year later, in February 2021, Lombardy was again in the headlines. An AP headline read, “Italy's Lombardy again in virus crisis as Brescia sees surge.” The article said, “Brescia, with a population of around 1.2 million, has seen its daily cases go from the mid-100s at the start of February to 901 on Wednesday and 973 Thursday,” meaning February 24th, 2021.]
Italy’s daily death toll peaked on March 27th at 919 and began falling. Rome in the south and Milan in the north each saw daily high temperatures beginning to clear 60 by mid-March, with lows above 40 every day after April 4th. Turin, with its higher elevation and grayer weather, saw lower highs but, as in the other cities, began clearing 40 on the low end by early April. Italy would remain in the worst ten countries for per capita coronavirus deaths, surrounded by other western European countries with similar weather, although the weather came to the northern countries later and stayed longer—and the coronavirus came later and killed more.