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Why Some People Are Asymptomatic. And More Science Journal News

The latest roundup of pandemic findings gathered by Hakai Magazine.

Brian Owens 3 Nov 2020Hakai Magazine

Brian Owens is a freelance science writer and editor based in St. Stephen, New Brunswick. His work has appeared in Hakai Magazine, Nature, New Scientist, the Canadian Medical Association Journal and the Lancet.

Compiled by veteran medical journalist Brian Owens, this roundup of some of the newest science on the COVID-19 pandemic, straight from the scientific journals, is presented by Hakai Magazine in partnership with The Tyee.

Aerosol microdroplets not as efficient at carrying virus

Aerosol microdroplets, the tiny particles that linger longest in the air when we speak, cough or sneeze, are not very efficient carriers of the SARS-CoV-2 virus. While the microdroplets are not risk-free, they carry less virus than larger droplets that fall to the ground quickly, so the risk from them is low in well-ventilated areas.

Physics of Fluids, Oct. 27, 2020

More data on the longevity of antibodies

The question of how long antibodies (and immunity) to COVID-19 last is vital to understanding how the pandemic will play out once vaccines become available. So far, studies have found varying results, with antibodies persisting anywhere between eight weeks and seven months.

A new study has come up with a time somewhere in the middle of that range — five months — and has helped reconcile the broad range found in previous studies. This new research found that the length of time antibodies last may depend on which part of the virus the antibodies are reacting to. The longer immunity lasts, the more effective a vaccine will be at bringing the pandemic under control.

Science, Oct. 28, 2020

Why meat processing plants are at high risk of outbreaks

Meat and fish processing plants have been the site of many COVID-19 outbreaks around the world, and an investigation of one such outbreak in Germany has shed some light on why — working conditions. Researchers found, for example, that confined spaces where unfiltered air is recirculated with little outside air exchange are dangerous. Also, the close proximity between workers engaged in physically demanding tasks that promote heavy breathing can aid infection, along with shared housing and transportation. Under these conditions, transmission can occur over distances of eight metres, the study found.

EMBO Molecular Medicine, Oct. 27, 2020

And other jobs at higher risk of infection

Health-care workers, grocery store staff, construction workers and people in the emergency services are among those with an elevated risk of contracting COVID-19 because of their job.

A study in Scotland found that health-care workers and their families made up 17 per cent of hospitalizations for COVID-19 among those under 65, with the highest risk among paramedics and emergency room staff. A study in New York City similarly found that firefighters and emergency medical workers were 15 times more likely to be infected than the general public. A study in Austin, Texas found that construction workers were five times more likely to be hospitalized with COVID-19 than workers in other occupations. And a study of grocery store workers in Boston found that they were also at higher risk of infection: 20 per cent compared with around one per cent in the general population. Alarmingly, three-quarters of the grocery workers who tested positive had no symptoms at the time of the test.

The British Medical Journal, Oct. 28, 2020

ERJ Open Research, Oct. 29, 2020

JAMA Network Open, Oct. 29, 2020

Occupational and Environmental Medicine, Oct. 30, 2020

Why are some people asymptomatic?

One of the reasons SARS-CoV-2 is so efficient at spreading is that most people take several days to develop symptoms after infection, and some remain asymptomatic throughout their illness. A new study sheds some light on why this is the case. It found that alveolar macrophages, the first set of immune cells the virus is likely to encounter in the lungs, do not react to SARS-CoV-2 in the way that they do to more familiar viruses, such as influenza. This puzzling behaviour suggests the virus can somehow hide from alveolar macrophages, giving it a head start on infection before the rest of the immune system is alerted to the virus’s presence.

EMBO Reports, Oct. 28, 2020

Fitness trackers can help detect COVID-19

Wearable devices like Fitbits are capable of identifying cases of COVID-19 by evaluating changes in heart rate and sleep and activity levels, alongside self-reported symptoms. This combination of data can identify cases with greater success than looking at symptoms alone. Researchers created a research app, MyDataHelps, to evaluate the possibility of using the devices to detect infections and found that they were able to pinpoint specific changes in sleep and activity levels that are indicative of COVID-19 versus other illnesses.

Nature Medicine, Oct. 29, 2020

Students fell behind because of school closures

The truncated 2019-2020 school year means that most students did not gain as much academically as usual, and lost more of those gains over the extended break than they would have over a normal summer holiday. Researchers estimate that returning students likely started school this fall with approximately 63 to 68 per cent of the typical annual learning gains in reading, and 37 to 50 per cent of the typical annual learning gains in math. The top one-third of students, however, may have made some gains in reading.

Educational Researcher, Oct. 28, 2020

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Trump voters less likely to physically distance

People in counties that voted for Donald Trump in the 2016 election tended to physically distance less between March and May this year than those in counties that supported Hillary Clinton. The study, which analyzed geotracking data from 15 million people, found a 24 per cent drop in regular activity in Trump counties, compared with a larger 38 per cent reduction in Clinton counties. These partisan differences in distancing were also associated with higher COVID-19 infection growth rates in pro-Trump regions.

Nature Human Behaviour, Nov. 2, 2020

Why some COVID-19 patients experience blood clots

One of the dangerous conditions associated with some cases of COVID-19 is blood clots in both large and small blood vessels. Now, researchers have found that a certain type of clot-promoting antibody is common in blood samples from many patients, which may be responsible for the clots. The antibodies may also provide a target for new therapies to treat the blood clots.

Science Translational Medicine, Nov. 2, 2020

Weather alone has no effect on COVID-19 spread

Temperature and humidity do not play a significant role in coronavirus spread, according to a new study. That means whether it’s hot or cold outside, the transmission of COVID-19 from one person to the next depends almost entirely on human behaviour.

The study found that the weather’s relative importance to the spread of the virus was less than three per cent, with no indication that a specific type of weather promoted spread over another. Human behaviour, on the other hand, was highly important. Taking trips and spending time away from home were the top two contributing factors to COVID-19 growth, with a relative importance of about 34 per cent and 26 per cent respectively. Population and urban density were the next two most important factors.

International Journal of Environmental Research and Public Health, Oct. 26, 2020

Superspreading events more common than thought

Superspreading events, in which one person infects more than six others, are much more common than expected, according to a new study of 60 such events. A mathematical model based on these results indicates that limiting gatherings to 10 or fewer people could significantly reduce the number of superspreading events and lower the overall number of infections.

Proceedings of the National Academy of Sciences, Nov. 2, 2020  [Tyee]

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