One Doplet Causes Covid, WHO Warns, UK Virus Death Spike, US Army: Get Vaxed or Get Out

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Exposure to one nasal droplet enough for Covid infection – study

Trial in which volunteers were given dose of virus is first to monitor people during entire course of infection

Lateral flow test
The study suggests lateral flow tests are a reliable indicator of whether infectious virus is present. Photograph: Jon Santa Cruz/Rex/Shutterstock

Exposure to a single nasal droplet is sufficient to become infected with Covid-19, according to a landmark trial in which healthy volunteers were intentionally given a dose of the virus.

The trial, the first to have monitored people during the entire course of infection, also found that people typically develop symptoms very quickly – on average, within two days of encountering the virus – and are most infectious five days into the infection.

The study was carried out using a strain of the virus before the emergence of the Alpha, Delta and Omicron variants.

The trial’s chief investigator, Prof Christopher Chiu, of Imperial College London, said: “Our study reveals some very interesting clinical insights, particularly around the short incubation period of the virus, extremely high viral shedding from the nose, as well as the utility of lateral flow tests, with potential implications for public health.”

The findings, published on Springer Nature’s pre-print server, and which have not yet been peer-reviewed, detail the outcomes in 36 healthy, young participants with no immunity to the virus. The volunteers were monitored at a specialist unit at the Royal Free hospital in London, and experienced no severe symptoms.

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The study found that the infection first appears in the throat and that infectious virus peaks about five days into infection, by which point the nose has a much higher viral load than the throat. The study also suggested that lateral flow tests are a reassuringly reliable indicator of whether infectious virus is present. Swabbing the nose and throat makes it more likely to detect infections during the first few days, the work suggests.

“We found that overall, lateral flow tests correlate very well with the presence of infectious virus,” said Chiu. “Even though in the first day or two they may be less sensitive, if you use them correctly and repeatedly, and act on them if they read positive, this will have a major impact on interrupting viral spread.”

The study also revealed that of the 18 people who became infected, all had similar viral loads regardless of whether they developed symptoms, underlining the role of asymptomatic transmission.

Prof Wendy Barclay, the head of the department of infectious disease at Imperial College London, said: “A lot of people could be walking around shedding virus and not realising. It’s really marked with this virus.”

Intriguingly, some of those who did not meet the threshold for being infected also had very low levels of virus detectable in their noses and throats, suggesting that they may have experienced a very short-lived infection that was seen off by immune activity in the lining of the nose and throat.

The team are expected to publish further findings giving a unique window into the earliest phase of the immune response, during the first hours and days after encountering the virus.

The team say the trial paves the way for future challenge studies that could help accelerate the development of the next generation of vaccines and antiviral drugs. Phase 3 studies have become increasingly difficult to plan due to the erratic levels of transmission in the population. Challenge studies are far quicker and require far fewer participants to establish efficacy.

Prof Sir Jonathan Van-Tam, the deputy chief medical officer for England, said: “Scientifically, these studies offer real advantage because the timing of exposure to the virus is always known exactly, therefore things like the interval between exposure and the profile of virus shedding can be accurately described.

“This important study has provided further key data on Covid-19 and how it spreads, which is invaluable in learning more about this novel virus, so we can fine-tune our response.”


WHO warns nations about lifting restrictions


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The head of the World Health Organization (WHO) warned countries against lifting their COVID-19 restrictions, saying the “virus is dangerous, and it continues to evolve before our very eyes.”

“We’re concerned that a narrative has taken hold in some countries that because of vaccines, and because of omicron’s high transmissibility and lower severity, preventing transmission is no longer possible and no longer necessary,” WHO Director-General Tedros Adhanom Ghebreyesus said during a media briefing on Tuesday.

“Nothing could be further from the truth. More transmission means more disease,” he continued.

Tedros said he did not believe that nations needed to return to lockdowns to curb further spread of the COVID-19 pandemic amid the spread of the highly transmissible omicron variant, but he said that nations could not rely on vaccination alone to solve the pandemic.

“It’s premature for any country either to surrender or to declare victory,” he said, noting that the WHO was currently tracking four sub-lineages of the omicron variant alone.

“We call on countries to continue testing, surveillance and sequencing. We can’t fight this virus if we don’t know what it’s doing,” he said. “And we must continue to work to ensure all people have access to vaccines.”


The Army announced on Wednesday that will begin separating soldiers who are not vaccinated against COVID-19.

Under a directive issued by Army Secretary Christine Wormuth, commanders will begin involuntary administrative separations for soldiers who have refused to be vaccinated and don’t have a pending or approved exemption request.

“Army readiness depends on Soldiers who are prepared to train, deploy, fight and win our nation’s wars,” Wormuth said in a statement. “Unvaccinated Soldiers present risk to the force and jeopardize readiness.”

Defense Secretary Lloyd Austin mandated vaccinations for the military in late August but left it up to each service to implement its own deadlines.

The Army gave active-duty soldiers until Dec. 15 to comply with the mandate, but Reservists and Army National Guard members still have until June 30 to be fully vaccinated.

As of Wednesday, service had yet to involuntary separate any soldiers solely for refusing the vaccine.

The Army has relieved six active-duty leaders — including two battalion commanders — for not complying with the mandate. It has also issued 3,073 written reprimands to soldiers who are not in compliance.



British health officials have reported the country’s highest daily COVID-19 death total in almost a year, Reuters reported.

Health officials said that on Wednesday 534 people died within a 28-day span of testing positive for COVID-19, per the wire service.

The reported deaths are the highest daily total since February 2021, according to Reuters.

According to data from the British government, 88,085 new virus cases were also recorded on Wednesday, the wire service reported.

This comes as countries around the world continue to deal with a surge of COVID-19 infections driven by the highly transmissible omicron variant.

British Prime Minister Boris Johnson apologized on Monday after a report on the gatherings he held on government property amid the ongoing pandemic found multiple “failures of leadership and judgment.”


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