XrayMuy

22/11/2021

Analysis of earliest covid-19 cases points to Wuhan market as source
A fresh look at what we know about the first covid-19 cases shows that the earliest known instance was in a person who worked at the Huanan market in Wuhan, which was suspected as the source from the start of the pandemic
An analysis of what we know about the earliest covid-19 cases has strengthened the argument that the coronavirus pandemic began when animals at the Huanan market in Wuhan, China, passed the virus on to people. Among other things, it concludes that the first case was a woman who worked as a seafood vendor at the market, who became ill on 11 December 2019.

It is clear that the SARS-CoV-2 virus derives from bat coronaviruses. What isn’t clear is where, when and how it got from bats into people. It has been suspected right from the start that live animals at the Huanan market might be the intermediate host, as the initial cases were clustered around this site.

A World Health Organization report on the origins of SARS-CoV-2, published earlier this year, states that the first person known to have covid-19 became ill on 8 December and had no connection to the market. This was partly why the report concluded that no firm conclusion about the role of the market could be drawn.

However, this man – a 41-year-old accountant living 30 kilometres away from the market – went to hospital on 8 December because of dental problems and only developed covid-19 symptoms on 16 December, says Michael Worobey at the University of Arizona in his analysis.

These dates are confirmed by media interviews with the accountant, hospital records and a scientific paper, Worobey says. That means that the earliest known cases were indeed linked to the market, with the first being the seafood vendor who became ill on 11 December.

Why this isn’t in the WHO report is unclear, as the team did speak to the accountant. “My guess is that they were told that this was the ‘December 8’ patient and just accepted it as read,” Worobey says. “But it would be interesting to learn more about that interview, for sure.”
When asked if their report had got it wrong, a WHO spokesperson said it was difficult to comment on particular cases. “The team did meet with some early patients, but those were not epidemiological interviews collecting health data that would put them in the timeline,” the spokesperson told New Scientist. “Those interviews were done by Chinese authorities in 2020.”

Overall, according to the WHO report, a third of 168 retrospectively identified cases in December had links to the Huanan market. This is in line with what one would expect if the market was the source, Worobey says. Because the original SARS-CoV-2 virus was highly infectious and could spread asymptomatically, many cases would soon lack a direct link to the source.
However, it has been suggested that this apparently strong link to the market is due to bias, because once authorities were alerted on 29 December, they specifically began looking for cases linked to the market.

Worobey says this can be checked by looking at what happened at the three hospitals where doctors first realised something was amiss. They had identified 19 unexplained pneumonia cases, of which 10 were linked to the market, before higher authorities were alerted.

“There was a genuine preponderance of early covid-19 cases associated with Huanan market,” he writes.

What’s more, not only are many early cases linked to the market, they are specifically linked to the western part of the market where live animals such as raccoon dogs were housed. Raccoon dogs are a potential intermediate host – they can be infected by SARS-CoV-2, but display few symptoms.

“Combined, this is compelling evidence that covid-19 has a live-animal-associated market origin much like the first SARS virus,” says David Robertson at the University of Glasgow, UK. “Whether the initial transmissions were from animals to customers in the market, via vendors or both is hard to say.”

Not everyone agrees. “There is nothing new in this article which could make a natural origin of SARS-CoV-2 more likely than a laboratory one,” says Rossana Segreto at the University of Innsbruck in Austria.

But other recent findings have weakened the case for a lab origin, which some researchers say was never strong. In particular, coronaviruses that are the closest match yet found to SARS-CoV-2 have been discovered in bats in Laos. These wild viruses have features in common with SARS-CoV-2 that some had claimed could only have arisen in a lab during so-called gain-of-function experiments, showing these features can and do evolve in the wild.

22/11/2021

mRNA vaccine against tick bites could help prevent Lyme disease
An mRNA vaccine that causes a red, itchy skin rash in response to bites by ticks may allow them to be removed before they transmit Lyme disease-causing bacteria
An mRNA vaccine designed to create an immune response to ticks so they can be removed before they transmit Lyme disease has been shown to be effective in guinea pigs. It is hoped the finding will pave the way for clinical trials in people.

Lyme disease is caused by a bacterium called Borrelia burgdorferi that is transmitted through tick bites. If left untreated, it can cause lifelong health problems like Lyme arthritis and nerve pain.

Erol Fikrig at Yale University and his colleagues have developed a vaccine that trains the immune system to respond to tick bites, by exposing it to 19 proteins found in tick saliva.

The vaccine contains mRNA molecules that instruct cells to make these proteins, in the same way that mRNA covid-19 vaccines direct cells to make coronavirus proteins.

Guinea pigs given the anti-tick vaccine developed red, itchy rashes when they were later bitten by ticks, suggesting their immune systems were responding. The ticks also tended to detach early without sucking as much blood as they normally would.

The researchers then placed ticks carrying Lyme disease-causing bacteria on vaccinated and unvaccinated guinea pigs. The ticks were removed from the vaccinated animals when their skin rashes emerged – usually in the first 18 hours – and none became infected with the bacteria. In contrast, half the unvaccinated animals became infected.

Even without this deliberate tick removal, the immune response generated by the vaccine may encourage the tick to fall off naturally before transmitting the harmful bacteria, says Fikrig.

The researchers will now test the vaccine in other animal models before beginning trials in people.

The anti-tick vaccine differs from other Lyme disease vaccines in development, which target the bacteria responsible rather than the tick carrier. Both approaches are promising, but one advantage of tick-targeted vaccines is that they may also protect against other tick-borne diseases like anaplasmosis and babesiosis, says Petr Kopáček at the Institute of Parasitology in the Czech Republic.

Fikrig hopes it will be possible to develop a vaccine that simultaneously targets the harmful bacteria and the ticks. “A combination of the two approaches might make a vaccine that is more effective than either one individually,” he says.

Other researchers are investigating whether Lyme disease could be eradicated in the wild by leaving out baits containing a chemical called hygromycin A that kills B. burgdorferi, but has little effect on most other bacteria and is harmless to animals.

22/11/2021

Milk allergy could be treated with gradual exposure to baked milk
Children who are severely allergic to milk may be able to start tolerating it if they are given tiny amounts of baked milk followed by progressively larger doses, a small clinical trial suggests. Larger studies are needed to confirm the effect and the therapy shouldn’t be attempted without medical supervision, doctors say.

About 3 per cent of preschool-aged children are allergic to proteins in cow’s milk, making it the most common food allergy in young children. Most naturally outgrow it by the time they go …

22/11/2021

22/11/2021