R0 goes down with rising temps and humidity. Covid has a pretty high R0 to begin with, so unlike flu and colds that almost disappear in summer, covid will most likely be slightly less contagious than in winter (people being more outdoors helps too). That’s not enough to make it not spread in warm countries now, but it will likely help some bad areas in colder climates such as New York or Germany.
Coronavirus is known to be less transmissible in the warmer seasons.
The long incubation period paused government intervention and bumped up the R0 value.
There is also the established pattern of coronavirus infections. In the northern hemisphere infections are at their worst from mid December to mid January. Near the equator the established pattern is a kind of double hump in the summer that peaks and fades around September which is what people saw. It is quite possible that at a macro level these patterns were repeated and attempts by people to contain the virus were of limited utility.
Weather: Maybe 10 oF increases the doubling time 2x (steady-state reduction in exterior virus levels by 50%
per Pubmed 22312351, plus reducing time × concentration of people indoors).
I don't think a paper about SARS-CoV-2 and temperature has been written yet (that I've seen), but people are hoping it reacts like SARS-CoV. See here: https://www.ncbi.nlm.nih.gov/pubmed/22312351
Keep in mind, that doesn't mean zero cases in hot weather, just that it is less contagious.
It’s a respiratory coronavirus. We have decades of info on respiratory viruses and other coronaviruses. They peak November to April in northern hemisphere countries with strong summers. See page 4 here: https://www.annualreviews.org/doi/pdf/10.1146/annurev-virolo...
The late August peak has been a southern US phenomenon, seemingly associated with going inside during warm months for air conditioning. The south states were the ones that peaked early both years. Israel also had an early summer peak last year, associated with a heat wave.
In states and countries where people go outside, it is a strong bet that viral transmission will be stronger in the months when coronaviruses are seasonally strong.
It was predicted because the change in weather causes more people to be indoors, and poor indoor air circulation is a big contributing factor for spreading. Same with the onset of the hot weather and A/C in the US South in May, around the time cases started increasing there.
Also, catching Covid sucks for a lot of people, even if they survive. Encouraging people to catch it during summer seems pretty irresponsible.
The much younger population is presumably a factor. Weather might be, too; cold places tend to see covid spikes in the winter, when everyone is indoors.
The disease has spread in places like Singapore and Thailand, which are warmer in February than most Northern Hemisphere cities are in summer. The notion that everything will just die down come Spring is blindingly optimistic.
My very amateur assessment of national and regional Covid trends is that higher rates of spread seem to correspond very highly with "indoors weather" conditions. That's heating season in colder climates, cooling season in warmer ones.
But yes: people gathering, indoors, largely with recirculated air.
It could be problematic, though, because lots of people travel during the summer. There are probably millions of people queued up to visit Italy, Spain, Britain, etc. The Europeans take long vacations, so populations will be particularly mobile in July and August.
I wonder if the U.S. might be slightly less vulnerable to contagion, since Americans tend to visit beaches, national parks and other less crowded places, whereas in Europe the tourist attractions are in crowded cities.
It's going to be an interesting few months before a vaccine is hopefully found.
I think the data shows that this coronavirus is causing drastically less illness in the past warmer months, as opposed to the months prior. This is consistent with SARS-1, other coronaviruses, as well as Influenza.
That's a different matter to the number of positive test results, which is indeed rising, but is not measuring actual illness.
As a Canadian, I’d caution against firm conclusions from our experience. I’m inclined to think first doses provide good protection, but cases collapsed last summer too despite a relaxing of NPIs. It is hard to overstate how much canadians are outside in summer vs. other seasons:
* School is out, university is out
* Air conditioning is comparatively rare. Or if present, unnecessary. People open their windows and doors instead. I’m typing this now with an open door with bug screen in front.
* Drivers roll down their windows
* People socialize outside in parks and backyards
* The population tans all of a sudden, raising vitamin D levels. Normal respiratory virus spread collapses
* Patios flourish at bars and restaurants. Often the inside is fairly empty. Window-walls open completely leaving restaurant/bar interiors open to the fresh air
* Many offices and professions have summer holidays
Then by mid September we hermetically seal ourselves inside and everyone gets sick once school is back.
I’m cautiously optimistic we’re past needing lockdowns but it is still too soon to tell. Our summer had a powerful seasonal effect last year and seems to have this year too.
(Past needing lockdowns = we’ll get enough new first and second doses in over summer while the season is on our side)
I know a lot of people are speaking out of their ass about this virus thing but I do believe our temperature has been a bit too cold for it to spread from objects, clothing and skin so far.
Also we've had amazing weather.
This last weekend I was in a 40 person pile up on a walking bridge near the beach here. Because someone wanted to take a perfect Instagram picture with his three dogs in the middle of the bridge.
I do also believe this virus thing is going to blow up in our faces soon, in these two coming months when temperatures get closer to 10-12 C daily.
So in hindsight we shouldn't have gone into WFH mode until april-may. And in June I believe it's going to be real heavy.
It's nice to hope that, but the virus doesn't seem to be struggling to spread in warm places. Curves in southern California, Louisiana, Australia are all following the standard trajectory.
Chinese immigrants visiting family for Chinese new year were a large source of initial infections in America, Canada, and Italy.
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