COVID DISCOVERIES - WHAT WE KNOW NOW THAT WE DIDN'T KNOW BEFORE

 The Guardian 6 August 2021 - by Nicola Davis

© Photograph: National Institute of Allergy an/AFP/Getty Images Sars-CoV-2 virus particles, isolated from a patient, captured and colour-enhanced.

Since the Covid pandemic took off in early 2020, researchers have been studying myriad aspects of the virus, and made some surprising discoveries. Here are four areas where our understanding has changed:

How Covid spreads

When Covid first hit the UK, so too did sales of hand sanitiser. On 28 February, Boris Johnson said: “The best thing people can do to prevent the spread of coronavirus is wash your hands.”

The emphasis was, in part, because it was thought one of the key routes by which Covid was spread was by people touching contaminated surfaces and then touching their own face – so called “fomite transmission”. Websites even appeared designed to alert you should you reach for your features, while many became concerned about whether to disinfect groceries and parcels.

But experts now argue that the role of tiny virus-containing particles called aerosols, emitted along with larger droplets when infected people breathe, speak or cough, were overlooked – and that ventilation in indoor settings is crucial to reduce the spread of Covid.

“The general consensus globally is now aerosol transmission [is more important] than handor contact transmission,” said Dr Julian Tang, a consultant virologist at Leicester Royal Infirmary. “This has changed dramatically from the initial emphasis on hand washing,” he said.

While contaminated surfaces are still noted as a likely transmission route by the World Health Organization, among others, it seems evidence is slim. “Despite consistent evidence as to Sars-CoV-2 contamination of surfaces and the survival of the virus on certain surfaces, there are no specific reports which have directly demonstrated fomite transmission,” the WHO has said.

However Prof Julian Hiscox, chair in infection and global health at the University of Liverpool, who is a participant in the New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), said while evidence has grown that aerosols matter it was still likely that the virus could be spread by directly touching infected people, or a surface on which an infected person had sneezed, so hand washing remains important.

Masks

Many experts and politicians dismissed the wearing of face coverings by the general public at the start of the pandemic.

“The suggestions people would make their own masks; whether it’s clothing and that sort of thing, which doesn’t really provide that much protection,” the transport secretary Grant Shapps told Good Morning Britain on 16 April last year.

“Secondly, the way people take it off can sometimes do the reinfection. Thirdly it can provide a false sense of security and actually there’s a fourth thing as well, if people are going for a higher level of PPE, then that can take it away from the frontline NHS care workers who really need it.”

However support for them has grown as evidence of their benefits have accrued: many scientists now say they help to catch virus-containing droplets and particles emitted by infected wearers while some have even said they offer some protection against infection to healthy wearers. That said, how effective they are depends on the type of mask, its fit, and what it is made from.

“My view on mask wearing has very much changed, because they do reduce aerosols,” said Hiscox. “I am more than happy to confess at the beginning of last year I thought that hand washing was more important than mask wearing … but now, yes I do think that [well-fitting] masks do play a role.”

The nature of the disease

The popular understanding of Covid was initially that it was only a respiratory infection, but as the pandemic has rolled on it has become apparent that other organs can be affected, directly or indirectly.

Researchers have found cases of blood clots, brain inflammation, delirium, stroke, heart abnormalities and liver and kidney damage among Covid patients.

Symptoms can also be ongoing for months after the initial infection – a condition that has been dubbed “long Covid”. While brain fog and fatigue are among the problems commonly reported, one study published last month suggested long Covid has more than 200 symptoms. However experts have noted “long-Covid” is a “catch-all” term and may reflect more than one syndrome. It also appears women are more likely to be affected than men.

Speaking at the Lords science and technology committee in September, Chris Brightling, professor of respiratory medicine of the University of Leicester who is leading the Phosp-Covid study into the long-term effects of the disease, said scans taken as part of the Phos-Covid and C-MORE studies were revealing the wider physiological impact of Covid-19.

“[These] are showing end-organ damage in the kidneys, in the liver, in the lungs and in the heart, and less so in the brain. This is affecting over a third of the individuals at the two-month point,” he said. “We are really getting a lot of clues that there are things that are happening across multiple organs from a disease that initially starts as a respiratory infection.”

Asymptomatic spreaders

The importance of asymptomatic infection has increasingly been recognised as important to Covid spread. While estimates vary, the UK government now says about one in three people infected with Covid do not develop symptoms.

In April, rapid lateral flow tests were made available for free to help pick up such infections – although some experts questioned the accuracy of the tests and a lack of focus on supporting those self-isolating. But earlier in the pandemic, when only PCR testing was available, the situation was very different.

“The UK’s decision to stop all community testing – due to inadequate resources/poor preparedness, and not to test mild/asymptomatic cases – likely led to the unchecked surge of community cases in the first wave,” said Tang.