On the 17th of January, we published the first estimates on the size of the 2019 novel coronavirus epidemic. These estimates suggested that the virus had infected substantially more people than had been confirmed at the time. On the 30th of January, the World Health Organization declared the novel coronavirus a public health emergency of international concern. I will now speak with Professor Neil Ferguson, Director of J-IDEA to give us an update on the current status of the novel coronavirus outbreak. The epidemic is continuing to spread internationally with more cases outside China being reported every day. Some notable ones like cruise ship in Japan giving us also an indication on how rapidly the disease spreads from person to person. In China, at the epicenter, Wuhan City, the case numbers appear to be flattering. To be sure, it's in line with predictions that the epidemic would peak in the next week or two at least. Very difficult to know what's really going on in China because they're using a case definition such that they only test people with really travel history to Wuhan province. So there are anecdotal reports of large surges in pneumonia cases in multiple cities across China, those are not currently reflected in official case numbers. We would expect the epidemic to be progressing in China from current data. What can we say about the severity of the coronavirus? I mean the team here has been working hard for the last last 2-3 weeks on trying to say something about really the range of clinical symptoms. In particular, the thing we're most concerned about, what proportion of people infected with this virus might die? It's a challenging question to answer because depending where you look, surveillance systems, hospitals, medical systems are picking up different ranges of severity. We think in China really, it's only the most severe cases have been tested for the virus. So based on a variety of data sources, official case reports and, then early case data from China, we estimate something of the order of 18 percent of cases in the epicenter, Wuhan may die. That's not to say 18 percent of everybody infected with the virus in Wuhan will die. We think separately that perhaps 35 percent of cases are actually being tested in that city. So we're seeing a severe tip of the iceberg and hence we get relatively high estimates of the proportion of those cases who might die. Another group we can look at is the cases of senior travelers, and there, we also have very little data to go on. We've only had two deaths, and well over 290 travelers diagnosed so far. That brings us to another challenge with doing this sort of calculation. There's a long delay from when somebody is diagnosed typically with this virus and where most people if they are going to die or will die. Something like three weeks we think from data in China. That's consistent with what we know from some SARS some 20 years ago for these sort of viruses. So when we look at deaths today, we might superficially have been reassured somewhat. We have only seen two deaths, 290 supported cases. But really, the deaths we see so far need to be compared with where the case numbers were. For instance, about two weeks ago because with an exponentially growing epidemic that's many fewer. So our estimates in that travel population, I mean there's a lot of uncertainty, but central estimates are between 2-5 percent roughly. Even that though, it doesn't really tell us the number we want to know, which is, in a large epidemic, what proportion of people infected might die? The reason it doesn't is that, there's been a lot of focus clearly on travelers coming into countries with apparent signs of illness. But the surveillance won't have picked everybody up, some people would've very mild disease. Some people infected may not show any symptoms at all, and so to get to that last number, we need an estimate of really what is the true number of people infected. The only data we have on that is actually from the flights which a number of countries repatriated their citizens back to, for instance, Germany and Japan. They swabbed everybody on those planes, took a nasal swab and tested it for virus. So that gives us a measure of what's called infection prevalence, what proportion of people infected irrespective of whether they have symptoms or not. We can go back and say, well, if those people were representative of everybody in Wuhan, and what does that imply about the size of the epidemic there? What that tells us is that calculation is really that the epidemic is overall three times larger than it would be even allowing for the travelers. So basically, countries around the world are probably detecting only one in three, one in four of the infected people coming in to those countries. That seems like bad news. In one respect, it's good news in the sense that it gives us another way of putting the reported deaths in the cases in travelers into perspective. You have to divide that crude number between two and five percent mortality by that level of under-reporting. Assuming the deaths are more likely to be protected, that gives us an estimate more like of the order of one percent of people infected with this virus might die, with enormous amount of uncertainty probably four fold in each direction. So anywhere from about a quarter of a percent, which is comparable with pandemic influenza viruses of 1968 and '97 pandemics all the way up to four percent, which would be more comparable with the 1918 Spanish flu epidemic. Your estimates have a large range of uncertainty. How useful does it make them? I think it informs what in the UK is called the reasonable worst-case scenario. It informs planning. The kind of scale of planning countries should be prepared to undertake. If we have even a relatively small risk of an epidemic with a large public health impact in terms of hospital beds occupied, severe illness, and death, then of course, it merits our currently correspondingly large preparedness effort. These efforts cost money, they divert resources, and so many informs those decisions. I don't think the estimates of the moment are at the level where we can be using them for predicting this year many people will die in the UK, for instance, or in any other country. But they do so. This is a serious threat which we need to plan for very seriously and dedicate resources to, and certainly that's what is happening in the UK and other countries. How many people might we expect to die in a country like the UK for instance? With just knowing what proportion of people being infected die, it doesn't tell you the overall impact on health mortality unless you know how many people you might expect to be infected overall. We don't have precise estimates of the attack rate at the moment, but we can go on the basis of past pandemics of respiratory disease. Really the best example there is influenza, and we know influenza pandemics varies. It probably cause about somewhere between 25 percent and 40 percent of the population to become sick in the first year. But some of those people have really quite mild disease, and then there's a hidden. What we never see is, there's something like another 20 percent or 30 percent of the population get infected, but really are not showing any symptoms. So that gives a complete attack rate. Percentage of the population can vary depending on the pandemic, and 60 percent might be a central estimate for the first year of people whose proportion population get exposed to the virus and become immune some of which developed symptoms. That's the number you then you multiply by the most broad definition of the case fatality ratio, the one where you look at what proportion of everybody who gets infected will die.
