Understanding Silent Spreaders

are very rare, before later clarifying her remarks. We explore why some people don't get sick after they're infected with the virus and why their role in its spread is still unclear. But first, here's what happened today. The World Health Organization said today that a persistent increase in cases in Latin America is of deep concern as hospitals across the region come under increasing strain. This comes one day after Anthony Fauci, the US government's top infectious disease expert,

said the pandemic is far from over. China is offering employees of some large state run companies the option to be inoculated with two vaccines currently in development. The government would only hand out the vaccine to workers intending to travel overseas. The European Union plans a gradual and partial easing of a ban on most travel to the block beginning July one. In May, the price of whitebread dropped the most since World War Two. That's according to the

Bureau of Labor Statistics. Dress prices and car insurance fell by the most on Kurt. Months of quarantine. It appears, have turned stay at home Americans into home bakers and lowered demand for anything but casual clothing as weakness across most categories pushed the overall consumer price index lower for a third month and now our main story. A comment by a w h O official earlier this week caught many health experts off guard. She threw doubt on what

has been accepted for months. Silent spreaders, carriers of the coronavirus who don't show symptoms readily transmit the disease to others. The official later clarified her comments, But just how risky are these asymptomatic carriers? Bloomberg Senior editor Jason Gale helps us untangle the issue. Back in February, the Diamond Princess cruise ship was the center of an explosive outbreak of

the coronavirus when it was quarantined in Japan. Of some three thousand, seven hundred and eleven passengers and crew on board the luxury ship, almost a fifth caught it at the time of testing. Surprisingly, most of those infected didn't have fever, dry cough, or difficulty breathing, the usual symptoms of COVID nineteen, and when doctors followed those asymptomatic cases for weeks, they found that just under half never developed

any disease. That contradicted initial findings from the World Health Organization. The agency said in March that asymptomatic infections are rare, but since then reports from around the world have shown that asymptomatic cases aren't swer rare, and in some instances they might be the source of infections. The majority of transmission that we know about is that people who have symptoms transmit the virus to other people through infectious ruplets.

That's Maria van Kirkhoff, the whose technical lead on COVID nineteen, speaking during a Facebook live event in Geneva on Tuesday. She was clarifying comments she made earlier in the week about the risk of the virus spreading from people who don't have symptoms. We do know that some people who

are asymptomatic. Are some people who don't have symptoms can transmit the virus on and so what we need to better understand is how many of the people in the population don't have symptoms, and separately, how many of those

individuals go on to transmit to others. The extent to which these silent carriers may also be silent spreaders isn't clear, and it probably varies between groups of people because the fact is, like age, genetics, underlying medical conditions, and people's individual and une responses, Uncertainty over how the virus behaves

has hindered nation's efforts to reopen bantered economies. If there are a lot of people in the community sharing crowded subway trains who don't know they're infected, well that's a big problem if they're also contagious. Dr Peter colign On, professor of medicine at the Australian National University in Canberra, says it's less likely individuals without respiratory symptoms will spread the virus simply because they're not coughing and spluttering on

other people. I actually do think asymptomatics cause less infection than symptomatics, maybe because they're not sneezing or coughing as much and therefore they're not spreading droplets as much. Is there's a few studies that show that of cases are due to people so super spreaders, but that still leaves who are dcovers for Since infected people without symptoms aren't in bed nursing their illness, they are typically more mobile,

which does present an infection risk. A simple nose rub could transfer virus party calls to a hand that could then touch a doorknob or a force it which someone else might touch and then rub their eye or mouth, inoculating themselves and causing an infection. So we've got to actually assume that people with minimum symptoms are still a risk for having the virus and being able to spread it. And that actually means that's good news in the community because it means we can keep on doing a whole

lot of things within limits. But we've got to just assume it's there at low levels and therefore take all the precautions we have to not let us spread. So the hand hygiene, the physical distancing don't go to work if you've got any symptoms, et cetera. That decreases the risk,

but it doesn't make the risk of zero. Peter says that in countries where the coronavirus is spreading out of control, it makes sense for public health officials to target symptomatic cases, isolate them and trace who they have been in contact with the monitor for further spread. But in countries where there is little or no obvious transmission going on, it is important to hunt down all infections. I think the asymptomatics are still important, particularly if you want to get

levels of virus at very low levels of transmission. I mean, if you're in a country where it's out of control, okay, yeah, concentrate on the symptomatics. I don't have a problem with that. But if you're in a situation like Career in New Zealand Australia, the the asymptomatics are also important to find um and once Europe gets down to low levels, that's going to be equally important because otherwise you find next

winter you're back in the same problem again. Infected people can also spread the virus via droplets that come out of them mouths in ways that don't require coffee. Dr SONJ Sent and I care An infectious diseases. Physician in Canberra says that could be important as communities come out of lockdown, especially in the context of large gatherings like protest marches. There may be certain scenarios where an asymptomatic person maybe create eating more droplets or perhaps even aerosolizing

a bit. For example, in a choir practice. We've had outbreaks in acquire setting in a loud nightclub where you have to shout a lot, or a protest or or some other event where someone won't be speaking normally. They might be therefore generating more droplets, and in that situation in a symptomatic person might be able to spread to someone else that way. So j I agrees that the likelihood of onward transmission is lower in a person without

respiratory symptoms compared with someone who's coughing. Problem is, there are a lot of people who are infected without symptoms, and there sheer number alone amplifies the risk of some

transmission occurring. There are a lot of asymptomatic infections out there and will only work out that proportion ultimately when we have a good antibody test, So good zero surveys will will give us that answer, And of course it is kind of hard because is someone truly asymptomatic if they're feeling a little bit under the weather, or are they actually symptomatic. So there are those those slight subtleties

in definition we have to think about. Jia says, the prospect that asymptomatically infected people are less likely to spread the virus doesn't mean we should abolish physical distancing and other measures to control the pandemic. Not now, not until we get a vaccine. I think we have to be very careful about that. Low risk is not no risk, and we've seen the consequences of what can happen if

there is a super spreader event. Uh, it has all the downstream effects, the impact on our health system, our economy, socially, it's just a disaster. So we have to be very very careful. But still except that asymptomatic transmission is lower risk, but it is still not no risk. The coronavirus US has a way of exploiting our vulnerabilities when we allow it to spread. Undetected cases can snowball quickly. The only sure fireway to counter it is to limit its ability

to infect others. As the w A chose said on Tuesday, in the absence of a vaccine, testing, quarantining and contact tracing remain our best defense against this insidious disease. That was Jason Gale, and that's our show today. For coverage of the outbreak from one bureaus around the world, visit bloomberg dot com slash coronavirus and if you like the show, please leave us a review and a rating on Apple Podcasts or Spotify. It's the best way to help more

listeners find our global reporting. The Prognosis Daily edition is produced by Topher Foreheads Jordan Gaspure, Magnus Hendrikson and me Laura Carlson. Today's main story was reported by Jason Gale. Original music by Leo Sedrin. Our editors are Francesco Levi and Rick Shine. Francesco Levi is Bloomberg's head of podcasts. Thanks for listening.