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Coronavirus: Can we stay safe as lockdown eases? - BBC News
As lockdowns ease, what are the risks of getting infected as people come into closer contact again?
Image copyrightGetty ImagesImage caption The new research suggests coughs and sneezes might project liquid further than previously thought As lockdowns are eased all over the world, what are the risks of getting infected as people come into closer contact with each other? It's a question that scientists have been exploring in a variety of settings including restaurants and offices. Frustratingly, the evidence for how the virus can be transmitted is often slim and if the answers seem vague it's because the science is uncertain. It comes amid pressure from businesses, such as pubs, to be allowed to reopen. But the influence is also coming from people wondering if the rules are too strict. What are the key factors? The most obvious is distance. Research that began in the 1930s showed that when someone coughs, most of the droplets they release either evaporate or fall to the ground within about one metre. That's why the World Health Organization (WHO) settled on its "one metre" rule for social distancing. Some governments have opted for a safer limit of 1.5m with the UK and others preferring an even more cautious 2m. The guidance essentially means that the further you're apart, the safer you ought to be but it's not distance alone that matters. The second key factor is timing - how long you're close to someone. Image copyrightReutersImage caption The UK government has adopted a 2m rule for social distancing The UK government's advice is that spending six seconds with an infected person 1m away carries the same risk as spending one minute with them if they're 2m away. And where it's not possible to keep your distance from a colleague, the aim is to limit the time together to 15 minutes. But as well as timing, there's another important issue: ventilation. Being outside carries the least risk because any virus released by someone infected will be diluted in the breeze. That doesn't mean the possibility of transmission is zero. Even out of doors, the UK's official advice is to stay 2m apart and, if you're closer, try not to talk face-to-face. But inside, where there isn't much fresh air and where people might be close together for longer, the chances of becoming infected are obviously greater. What are the risks indoors in a restaurant? A fascinating insight comes from a study in the Chinese city of Guangzhou which tracked how a cluster of infections occurred. Sitting at tables that were one metre apart, people were having a meal last January. One of the diners was infected with coronavirus but hadn't realised because they had no symptoms. But in the following days, another nine people who'd been in the restaurant at the time came down with Covid-19 - including five who'd been sitting at other tables several metres away. Scientists investigating the infections reached a conclusion about the most likely route of transmission: that droplets containing the virus - released by the infected person - were circulated by air conditioning. "The key factor for infection was the direction of the airflow," their study says, blaming two air conditioning units mounted high on a wall. This is not proof that the virus can be spread this way but the research certainly suggests that it is a plausible route. And, if confirmed, it would mean that in any room with a similar system of ventilation, even moving tables more than one metre apart would still not guarantee to keep people safe. What do we know about the effect of ventilation? To try to understand the risks, a team from the University of Oregon, specialising in the study of microbes in buildings, simulated different types of ventilation in a restaurant. In one scenario, someone at a corner table coughs without covering their mouth and releases droplets and particles that are projected through the air. The largest droplets land on their own table - that's what you'd expect with the WHO's 'one metre rule'. Image copyrightUniversity of OregonImage caption Computer modelling by the University of Oregon showing the potential spread of coronavirus in a restaurant with an air conditioning unit But smaller ones reach beyond the immediate area and are caught in a current of air coming from an air conditioning unit at the other end of the room. The result is similar to what's thought to have happened in the restaurant in Guangzhou: tiny droplets and particles are spread to people at other tables. As with that study, this simulation doesn't prove that the coronavirus can be transmitted this way or, if it did, that it would make anyone ill. That depends on whether the virus is still active after being blown across the room and on whether the person receiving it gets a large enough "dose" - but the possibility of infection can't be ruled out. According Kevin Van Den Wymelenberg, professor of architecture at the University of Oregon, who led the study, the virus "can be spread further than people might realise". What can be done to make restaurants safer? The Oregon team simulated another scenario in the same restaurant in which there's an open window beside the person who coughs and an extractor vent on the opposite wall. This time the cloud of droplets and particles is not pushed around the room but instead travels in a fairly direct line from window to vent with the result that fewer people are caught in it. A flow of fresh air to dilute the virus is one of several techniques highlighted by the team as options for managing Covid-19. Image copyrightUniversity of OregonImage caption The simulations showed how fresh air from an open window could carry the virus to a vent "It's really impossible to completely eliminate risk," says Prof Van Den Wymelenberg, "but what we showed was a concept for how you could reduce transmission." "The good news is that there are things you can do to make safer spaces." In addition to bringing in fresh air through windows or mechanical ventilation, other options include improving the standard of filtration and also humidifying the air - moist conditions might encourage droplets to sink to the floor. What does this mean on planes? Social distancing isn't likely to be possible - unless the aircraft is half empty - and by definition you'll be in close contact with others for more than 15 minutes. So on the basis of those two key factors, the risks may well be higher. The question of ventilation is more debatable. On the one hand, the air in the cabin is constantly circulated so if someone coughs, even a few rows away, there is a chance the infection will be spread. On the other hand, modern aircraft filter the cabin air every few minutes and to a high standard. What about the risks at work? In factories and offices, social distancing may be harder to follow. Dr Julian Tang of the University of Leicester has come up an easy "breath test" to check if you're too close to colleagues. A consultant virologist at Leicester Royal Infirmary, he's studied how the air is moved when people speak and concludes that something as simple as a conversation could pass the virus. "If you can smell your friend's breath - the garlic or curry or alcohol - you're inhaling what they're breathing out. "And if you're inhaling enough of that air to smell it, then you're close enough to inhale any virus that's also carried in the air with it." So how can transmission take place? So far the public advice has focused on what's called the "droplet" route, someone coughing or sneezing into the eyes, nose or mouth of a person nearby, which has led to the social distancing rules. It's also highlighted a second route - surfaces - in which a person who's infected passes on the virus through contact either directly by shaking hands or by exhaling over surfaces like kitchen worktops. Image copyrightHexagon/MSCImage caption Modelling by Hexagon/MSC Software showing how an infected person could pass the virus to a fellow passenger on a train. Others then get the contamination on their hands, directly or by using the same space at work or at home - which is why handwashing is so important. But there's a third possibility as well - tiny droplets or particles being carried in the air by speech, for example and that roite might be the most important, according to Dr Tang. "When you're talking to a colleague you don't touch them, you don't spit on them, most of the interaction is by voice and breathing." All of which reinforces the idea that there isn't one way to stay safe: it involves social distancing and keeping any close contacts brief and checking for healthy ventilation. Follow David on Twitter.
Megaraptor: Fossils of 10m-long dinosaur found in Argentina - BBC News
Palaeontologists say the remains date back 70 million years, close to the end of the dinosaurs.
Image copyrightReutersImage caption The fossils were found during field work in Patagonia Palaeontologists have found the fossils of a new megaraptor in Patagonia, in the south of Argentina. Megaraptors were large carnivorous dinosaurs with long arms and claws measuring up to 35cm (14in) in length. They also had powerful legs and long tails which made them more agile than the Tyrannosaurus rex and allowed them to catch smaller herbivorous dinosaurs. The new megaraptor is one of the last of its group, before dinosaurs became extinct, the scientific team says. What did the scientists find? The team led by Fernando Novas from the Natural Sciences Museum in Buenos Aires discovered many fossils during its month-long field work in Estancia La Anita, in southern Santa Cruz province. You may also be interested in: The most unusual ones were the remains of a large carnivorous dinosaur belonging to the Megaraptoridae family. The scientists uncovered vertebrae, ribs and part of what would have been the dinosaur's chest and shoulder girdle. Image copyrightArgentine Natural Science MuseumImage caption A large number of fossils have been found in Patagonia, in Argentina's south The fossils they found belonged to a specimen measuring approximately 10m (33ft) in length, one of the largest of the Megaraptoridae found so far. In a statement [in Spanish], the team said that the remains date back 70 million years - towards the end of "the age of the dinosaurs". Fernando Novas told Reuters news agency that "this new megaraptor that we now have to study would be one of the last representatives of this group" before the dinosaurs became extinct. What did it look like? The megaraptor had long, muscular arms with sickle-like claws and a long tail which provided it with balance. Slimmer and more agile than the T. rex it is thought to have used its arms and claws rather than its jaw as its main weapon when hunting its prey. "It had powerful and elongated legs which allowed it to take big steps," palaeontologist Aranciaga Rolando said. The scientists from the Natural Sciences Museum believe it would have used its speed to hunt ornithopods, plant-eating dinosaurs which walked on two legs. You may want to watch: Media captionA giant dinosaur thigh bone is excavated in France
Coronavirus: US health official warns of dangerous second wave - BBC News
The top US health official warns a fresh outbreak could coincide with the flu season.
Image copyrightGetty ImagesImage caption The US has reported the most coronavirus cases in the world A second wave of coronavirus cases in the US could be even worse than the first, the country's top health official has warned. Centers for Disease Control and Prevention (CDC) director Robert Redfield said the danger was higher as a fresh outbreak would likely coincide with the flu season. It would put "unimaginable strain" on the US health care system, he said. The US has seen more than 800,000 cases - the highest in the world. More than 45,000 people have so far died with coronavirus across the US, according to a tally kept by Johns Hopkins University. California had its highest one-day rise in new cases on Monday while New Jersey, the worst-hit US state apart from New York, saw its highest increase in deaths in one day. In other developments in the US:
- President Trump says he will halt applications for US green cards - which give immigrants legal permanent residence and the opportunity to apply for American citizenship - for 60 days
- Harvard University says it will keep an $8.6m-coronavirus grant despite pressure from President Trump to return it
- California's first cases of coronavirus occurred much earlier than previously thought, health officials have confirmed. A post-mortem examination has revealed that a person who died at home on 6 February in Santa Clara county is now the first known fatality in the US. Until now, the first fatality was thought to have been a man in Washington state who died on 26 February
- The US Senate has unanimously approved $484bn (£392bn) in coronavirus relief, including funds designed to help small businesses. The legislation will go to the House of Representatives for approval on Thursday