How the Delta variant achieves its ultrafast spread

‘Viral load is roughly 1,000 times higher in people infected with the Delta variant than those infected with the original coronavirus strain, according to a study in China...

‘The combination of a high number of viruses and a short incubation period makes sense as an explanation for Delta’s heightened transmissibility, says epidemiologist Benjamin Cowling at the University of Hong Kong. The sheer amount of virus in the respiratory tract means that superspreading events are likely to infect even more people, and that people might begin spreading the virus earlier after they become infected.

‘And the short incubation makes contact tracing more difficult in countries such as China, which systematically tracks each infected person’s contacts and require them to quarantine. “Putting it all together, Delta’s really difficult to stop,” Cowling says.’

Read here (Nature, July 21, 2021)

Could a cheap iodine mouthwash really help to beat Covid?

‘We all probably have a sense-memory of iodine: the blood-like drop to purify a camping can of stream-water or the inky dab with which your grandmother stained your grazed knee. It feels like an old-fashioned, primitive home remedy, yet could it also be an intriguing new weapon against our most modern threat: coronavirus?

‘One of the world’s leading authorities on infection in the mouth and nose believes the answer is yes. Stephen Challacombe is a professor of oral medicine at King’s College London, with a specialism in the immunology of the mucous membranes. His decades of experience meant that when the pandemic hit, his mind went immediately to one — literal — solution. Iodine mouthwash. “Yes. I have no doubt that this should be used,” Challacombe says, “and had it been, it would have saved lives.”

‘Bottles of this form of iodine, called povidone-iodine, also known by the most common brand Betadine, used to be on sale in British chemists, before the public began to favour fluoride rinses. It is still popular as a sore-throat gargle in many European countries, America, Australia and Far East countries such as Japan. When the pandemic struck, Challacombe and his colleagues wrote to the British Dental Journal reminding the scientific world of its potential.’

Read here (King's College Journal, Nov 9, 2020)

US Covid-19 cases are skyrocketing, but deaths are flat—so far. These 5 charts explain why

 ‘In just the last two weeks, the global daily tally for new COVID-19 cases has jumped more than 30%, according to TIME’s coronavirus tracker, which compiles data from Johns Hopkins University. The steep upward trend is driven by viral waves in Europe and the United States that started in August and mid-September, respectively. On Oct. 23, the daily case count in the U.S. reached a new record high, suggesting that this wave will be worse than the one that swept the country over the summer.

‘But despite this rapid uptick in cases, the daily death count in the U.S. is not yet rising at the same rate, and remains at lower levels than in April. At face value, a lower case-to-fatality rate suggests that fewer people who test positive for the virus are dying from it. But the virus hasn’t necessarily become less lethal; it isn’t mutating quickly enough for that to be the case.

‘What’s happening now is not a result of how the virus treats humans, but rather how humans are treating the virus—that is, how we test for it, how we avoid it and how we combat it. The following five charts explain how human-driven factors are, at least for the moment, keeping deaths from spiking as high as they did early in the pandemic, even as cases rise dramatically...’

Read here (Time, Oct 26, 2020)

Face masks could be giving people Covid-19 immunity, researchers suggest

‘Face masks may be inadvertently giving people Covid-19 immunity and making them get less sick from the virus, academics have suggested in one of the most respected medical journals in the world.  The commentary, published in the New England Journal of Medicine, advances the unproven but promising theory that universal face mask wearing might be helping to reduce the severity of the virus and ensuring that a greater proportion of new infections are asymptomatic. 

‘If this hypothesis is borne out, the academics argue, then universal mask-wearing could become a form of variolation (inoculation) that would generate immunity and “thereby slow the spread of the virus in the United States and elsewhere” as the world awaits a vaccine. It comes as increasing evidence suggests that the amount of virus someone is exposed to at the start of infection - the “infectious dose” - may determine the severity of their illness. Indeed, a large study published in the Lancet last month found that “viral load at diagnosis” was an “independent predictor of mortality” in hospital patients.’

Read here (The Telegraph, Sept 12, 2020) 

Viral loads: Review points to PCR-testing inadequacies and need to prioritise early case detection

A review of 79 studies on viral loads in people — specifically, SARS-CoV-2, SARS-CoV-1 and MERS-CoV — has shown that (1) ‘viral RNA can persist in and be shed from the body for long periods of time (more than 80 days in some cases)’ although ‘SARS-CoV-2 only remains viable and infectious for approximately one week after the onset of symptoms’ (2) ‘Viral load was at its highest approximately 3-5 days after the onset of symptoms, and there was a positive correlation between prolonged viral shedding and disease severity. Older patients also experienced prolonged viral shedding compared to younger patients, even when accounting for disease severity...

‘While there are fewer studies on the kinetics of viral load for asymptomatic infections, viral shedding appeared to be of a shorter duration, and overall viral load appeared to be lower compared to symptomatic cases.’ 

The authors conclude that (1) ‘PCR testing is likely not a good tool for evaluating patient recovery, because viral RNA is detectable long after the end of the infectious period’. (2) ‘Early case detection and isolation should be prioritised in order to maximise control efforts during the time when patients are the most infectious.’ -- Center for Health Security, John Hopkins University

https://www.medrxiv.org/content/10.1101/2020.07.25.20162107v2.full.pdf

Read here (Medrxiv, July 25, 2020)

Experts dispute reports that coronavirus is becoming less lethal

‘Has the novel coronavirus in Italy changed in some significant way? That was the suggestion of a top doctor in northern Italy who reports that patients to his hospital have been showing up with lower levels of the virus in their upper respiratory tracts compared with those two months ago.

‘The comments, which received widespread attention following a Reuters report, prompted vigorous pushback from Michael Ryan, a top official with the World Health Organization, who said Monday during an online news conference that “we need to be exceptionally careful not to create a sense that all of a sudden the virus by its own volition has now decided to be less pathogenic. That is not the case at all.”

Read here (Washington Post, June 2, 2020)

New coronavirus losing potency, top Italian doctor says

‘The new coronavirus is losing its potency and has become much less lethal, a senior Italian doctor said on Sunday. “In reality, the virus clinically no longer exists in Italy,” said Alberto Zangrillo, the head of the San Raffaele Hospital in Milan in the northern region of Lombardy, which has borne the brunt of Italy’s coronavirus contagion. “The swabs that were performed over the last 10 days showed a viral load in quantitative terms that was absolutely infinitesimal compared to the ones carried out a month or two months ago,” he told RAI television.’

Read here (Reuters, June 1, 2020)

Coronavirus replicates in throat making it easy to transmit, German scientists say

‘Pathogen that causes Covid-19 does not have to travel to the lungs to replicate, researchers say. High viral load in the throat at the onset of symptoms suggests people with Covid-19 are infectious very early on, they say.’

Read here (South China Morning Post, April 9, 2020)

Mild cases as infectious as severe ones? There are strong correlations in Lombardy and Guangzhou. If proven true, this would underscore the need for tweaking social-distancing policies for the longer term...

 ‘If you have a high viral load, you are more likely to infect other people, because you may be shedding more virus particles. However, in the case of covid-19, it doesn’t necessarily follow that a higher viral load will lead to more severe symptoms.

‘For instance, health workers investigating the covid-19 outbreak in the Lombardy region of Italy looked at more than 5,000 infected people and found no difference in viral load between those with symptoms and those without. They reached this conclusion after tracing people who had been in contact with someone known to be infected with the coronavirus and testing them to see if they were also infected.

‘Similarly, when doctors at the Guangzhou Eighth People’s Hospital in China took repeated throat swabs from 94 covid-19 patients, starting on the day they became ill and finishing when they cleared the virus, they found no obvious difference in viral load between milder cases and those who developed more severe symptoms...

‘It is early days, but if the infectious dose doesn’t correlate with the severity of disease symptoms, this would mark covid-19 out as different from influenza, MERS and SARS...’

Read here (New Scientist, March 27, 2020)