Coronavirus research recap: Delayed immune system response, Covid stress, and theory on masks



READ | Covid-19: More reasons why men and the elderly are hit harder

Older people, as well as those with comorbidities, have been found to be more vulnerable to severe Covid-19, the disease caused by SARS-CoV-2, since the early stages of the pandemic. And more recently, it has become clear why men as a group are also hit harder by the disease.

According to a latest study published in the open-access journal PLOS Biology this month, it appears that delayed immune response may drive higher Covid-19 mortality rates among men and the elderly.

In August, Health24 reported on a study involving a team of researchers who analysed factors such as viral loads and the immune response in both males and females to find clues as to why men seem to be more susceptible to contracting Covid-19.

Among their observations was that females tend to produce more disease-fighting T-cells than males.

In spite of SARS-CoV-2’s minimal genetic diversity, the manifestation of Covid-19 infection has been found to vary among different patients. In the latest study, scientists, from the University of Washington wanted to understand the underlying mechanism that causes such diverse reactions in different hosts.

They extracted and sequenced viral RNA from swabs collected from 430 Covid-19 positive cases and 54 negative controls, and analysed the hosts' antiviral and immune responses across infection status, viral load, age and sex.

The researchers found that immune cell responses were not activated until after three days following the onset of infection.

They also wrote that the immune cell composition and function fluctuated with viral loads, suggesting a dysfunctional antiviral response in males and the elderly.

READ | Stress from Covid-19 may be hard to shake, even with exercise

Exercise has many physical and mental benefits and may offer much-needed structure and routine to your day, especially while working from home during the coronavirus pandemic.

But if your stress and anxiety levels are through the roof because of Covid-19, even exercise may not be enough to alleviate this, researchers from Washington State University have found.

In a study, recently published in the journal PLOS ONE, researchers looked at data from over 900 pairs of identical and same-sex fraternal twins from the Washington State Twin Registry.

Those who did less exercise within two weeks after stay-at-home orders were announced, had perceived higher levels of stress and anxiety. But, contrary to expectation, those who increased their levels of physical exercise during the same period did not experience lower levels of stress and anxiety.

"Certainly, people who don't exercise know that there are associations with mental health outcomes, yet the ones that increased their exercise also reported increased anxiety and stress," said lead author Glen Duncan, a professor in WSU's Elson S. Floyd College of Medicine in a press release. "It's hard to know exactly what's going on, but it could be that they are trying to use exercise as a means to counter that stress and anxiety they're feeling because of COVID."

The reason why the researchers decided to use twins was to investigate whether the associations between changes in physical activity and mental health were influenced by genetic traits, environmental factors or both.

They found that both genetic and environmental factors accounted for the association between less exercise and stress. And where one twin did less exercise and experienced increased levels of stress, the other twin’s stress levels didn’t decrease with more exercise. "It's not necessarily that exercise won't help you personally manage stress," said Duncan. "It's just that there is something genetically and environmentally linking the two."

The researchers stated that even though exercise didn’t drastically decrease stress levels in the short term, they are planning to do the survey again to see the effect of exercise in the long term.

READ | Could your mask be a kind of vaccine against Covid-19?

The world is still waiting for a safe, effective coronavirus vaccine. But new research now suggests that billions of people may already be using a crude vaccine of sorts: face masks.

The theory – and it remains largely a theory – is that by filtering out airborne coronavirus droplets and thereby lowering the dose of SARS-CoV-2 a person inhales, infections have much less chance of producing symptoms.

Much in the way vaccination works, an immune response would be triggered in the mask-wearer upon contact with a small amount of virus, but at a level that's not likely to cause serious illness.

"If this theory bears out, population-wide masking, with any type of mask that increases acceptability and adherence, might contribute to increasing the proportion of SARS-CoV-2 infections that are asymptomatic," said Dr Monica Gandhi and Dr George Rutherford in a commentary published on 8 September in the New England Journal of Medicine. Both authors are from the University of California, San Francisco.

There's some good evidence that masks could be working in this way, according to the two experts. They pointed out that animal studies conducted since the 1930s have borne out the notion of a "lethal dose", or how many viral particles are needed to cause severe disease.

More recently, studies conducted in hamsters seem to show that "higher doses of administered virus led to more severe manifestations of Covid-19", Gandhi and Rutherford wrote. And when the hamsters were protected with simulated masking, they "were less likely to get infected, and if they did get infected, they either were asymptomatic or had milder symptoms than unmasked hamsters," the experts noted.

For ethical reasons, similar trials in humans haven't been conducted. But population studies seem to support the "mask as vaccine" theory. For example, the US Centers for Disease Control and Prevention reported that by mid-July about 40% of coronavirus infections were asymptomatic, but in areas of the United States where mask-wearing was very prevalent, that number rose to 80%.

In early outbreaks of SARS-CoV-2 infections on cruise ships, before the widespread use of face masks, the rate of cases with no symptoms was about 20%, Gandhi and Rutherford noted. But in an outbreak on one Argentinian cruise ship where face masks were mandated for passengers and crew, the rate of asymptomatic cases rose sharply, to 81%.

READ | Asthma may not boost odds of severe Covid-19

New research may have people with asthma breathing a little easier: Doctors found the airway disease doesn't raise the risk of being hospitalised due to Covid-19.

The researchers also noted that people with asthma weren't more likely than people without it to need a ventilator to help them breathe.

"A lot of people with asthma think they have a predisposition to severe Covid, and they worry a lot about going out. They should take precautions like using their masks, but they may not need to worry so much," said study author Dr Fernando Holguin. He's director of the Asthma Clinical and Research Program at the University of Colorado Anschutz Medical Campus, in Aurora.

Holguin said the proportion of hospitalised Covid-19 patients with asthma was around 6%.

"For most places, that's an asthma prevalence that is at or lower than the asthma prevalence in the general population. To compare, with influenza [flu], we typically see about a quarter of those in the hospital have asthma," he said.

When the pandemic first began, the US Centers for Disease Control and Prevention suggested that people with asthma had a higher risk of hospitalisation and other severe outcomes. People with asthma do have a significantly higher risk of complications with flu, another viral infection.

In the new study, the researchers reviewed 15 studies on Covid-19 infections to see how many people hospitalised had asthma. They also looked at more than 400 patients treated for Covid-19 at the University of Colorado Hospital, to see whether the rates of ventilator use were different in people with asthma.

"The message from our study is not to be cavalier about Covid, but individuals with asthma won't do worse than people without it," Holguin said.


SA cases update: 

The latest number of confirmed cases is 649 793.

According to the latest update, 15 447 deaths have been recorded in the country.

There have been 577 906 recoveries.

So far, more than 3.91 million tests have been conducted, with 15 692 new tests reported.

Global cases update:

For the latest global data, follow this interactive map from Johns Hopkins University & Medicine.

Late on Sunday night, positive cases worldwide were more than 28.84 million, while deaths were more than 921 000.

The United States had the most cases in the world - more than 6.5 million, as well as the most deaths - almost 194 000.

HEALTH TIPS (as recommended by the NICD and WHO)

• Maintain physical distancing – stay at least one metre away from somebody who is coughing or sneezing

• Practise frequent hand-washing, especially after direct contact with ill people or their environment

• Avoid touching your eyes, nose and mouth, as your hands touch many surfaces and could potentially transfer the virus

• Practise respiratory hygiene – cover your mouth with your bent elbow or tissue when you cough or sneeze. Remember to dispose the tissue immediately after use.

Image credit: Getty Images

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