This article is from the source 'guardian' and was first published or seen on . It last changed over 40 days ago and won't be checked again for changes.

You can find the current article at its original source at https://www.theguardian.com/global-development/2020/feb/06/hidden-coronavirus-cases-could-thwart-containment-efforts-experts-warn

The article has changed 2 times. There is an RSS feed of changes available.

Version 0 Version 1
'Hidden' coronavirus cases could thwart containment efforts, experts warn 'Hidden' coronavirus cases could thwart containment efforts, experts warn
(32 minutes later)
Failure to report mild symptoms combined with highly contagious nature of disease raises fears existing figures are ‘tip of the iceberg’Failure to report mild symptoms combined with highly contagious nature of disease raises fears existing figures are ‘tip of the iceberg’
Global health experts have warned that “hidden” infections make containment of the coronavirus unlikely and raised fears that the rapidly rising caseload of 25,000 people could be the “tip of the iceberg”.Global health experts have warned that “hidden” infections make containment of the coronavirus unlikely and raised fears that the rapidly rising caseload of 25,000 people could be the “tip of the iceberg”.
“Hidden” cases – where people with mild symptoms do not seek medical help and so remain untested and unrecorded – combined with the highly contagious nature of the disease mean there could be “vastly more cases” than previously thought, according to Tom Frieden, a former director at the US Centers for Disease Control and Prevention. “Hidden” cases – where people with mild symptoms do not seek medical help and so remain untested and unrecorded – combined with the highly contagious nature of the disease mean there could be “vastly more cases” than previously thought, according to Tom Frieden, a former director at the US Centers for Disease Control and Prevention.
“It’s becoming increasingly clear that containment is very unlikely,” said Frieden, who now heads Resolve to Save Lives, an NGO focusing largely on preparedness for infectious diseases.“It’s becoming increasingly clear that containment is very unlikely,” said Frieden, who now heads Resolve to Save Lives, an NGO focusing largely on preparedness for infectious diseases.
“It probably isn’t worth giving up, but trying to contain Wuhan coronavirus like Sars and Mers is very unlikely, just because of the number of cases and the number of [Chinese] provinces and the ease with which it is ease spreading in families.“It probably isn’t worth giving up, but trying to contain Wuhan coronavirus like Sars and Mers is very unlikely, just because of the number of cases and the number of [Chinese] provinces and the ease with which it is ease spreading in families.
“It’s a fog of war reality, which is what makes me suspect that what are seeing is the tip of the iceberg.”“It’s a fog of war reality, which is what makes me suspect that what are seeing is the tip of the iceberg.”
Frieden added that while such confusion is common in every outbreak, what marks this one as different is the very large number of cases and how contagious the virus appears to be, although he added that the relative death rate was likely to diminish as more mild cases were identified.Frieden added that while such confusion is common in every outbreak, what marks this one as different is the very large number of cases and how contagious the virus appears to be, although he added that the relative death rate was likely to diminish as more mild cases were identified.
Researchers have identified a time lag of reporting infections of one to two weeks, while estimating a doubling in the number of infections roughly every six days, making the real figure at least 75,000.Researchers have identified a time lag of reporting infections of one to two weeks, while estimating a doubling in the number of infections roughly every six days, making the real figure at least 75,000.
Dr Nathalie MacDermott, a clinical lecturer at King’s College London, said: “The mortality rate is literally the number of people dying as a proportion of cases of the disease. It is currently likely to be an overestimate, based on milder cases of the disease not being identified. But it is not accurate. What’s missing is the number of people with a milder form.”Dr Nathalie MacDermott, a clinical lecturer at King’s College London, said: “The mortality rate is literally the number of people dying as a proportion of cases of the disease. It is currently likely to be an overestimate, based on milder cases of the disease not being identified. But it is not accurate. What’s missing is the number of people with a milder form.”
For example, if 400 deaths and 20,000 cases are reported, the mortality rate is 2%, she said. “But if you divide the deaths by 75,000, you would get a rate of 0.5%.”For example, if 400 deaths and 20,000 cases are reported, the mortality rate is 2%, she said. “But if you divide the deaths by 75,000, you would get a rate of 0.5%.”
Mild cases have the potential for making containment more difficult, she said.Mild cases have the potential for making containment more difficult, she said.
Asked if measures taken in China to contain the virus were effective, she said it was too early to tell, particularly because of the time lag, which also might change. “We are not clearly seeing an impact at the moment. We would need to monitor for a month or so.”Asked if measures taken in China to contain the virus were effective, she said it was too early to tell, particularly because of the time lag, which also might change. “We are not clearly seeing an impact at the moment. We would need to monitor for a month or so.”
Exponential spread of the virus in other cities outside China was unlikely, added MacDermott. “We haven’t so far seen a significant spread in cities outside China. In cases outside China we are still watching. So we could get a shock. But we probably won’t see a Wuhan situation in other countries. We could see a surge in other Chinese cities, particularly as there is a 14-day incubation period, so there might be a time lag in identifying all cases.”Exponential spread of the virus in other cities outside China was unlikely, added MacDermott. “We haven’t so far seen a significant spread in cities outside China. In cases outside China we are still watching. So we could get a shock. But we probably won’t see a Wuhan situation in other countries. We could see a surge in other Chinese cities, particularly as there is a 14-day incubation period, so there might be a time lag in identifying all cases.”
Professor David Heymann, who led the World Health Organization’s infectious disease unit at the time of the Sars outbreak, urged caution, saying it was too soon to accurately predict the spread of the virus.Professor David Heymann, who led the World Health Organization’s infectious disease unit at the time of the Sars outbreak, urged caution, saying it was too soon to accurately predict the spread of the virus.
“What’s important is the cases outside of China,” said Heymann. “Inside China there is a lot of disorder in the health system, because it is overstretched. Patient management has to come first. But with a victim outside China, you can follow that case and see how others are being infected, by observing the reproduction rate and the spectrum of disease.“What’s important is the cases outside of China,” said Heymann. “Inside China there is a lot of disorder in the health system, because it is overstretched. Patient management has to come first. But with a victim outside China, you can follow that case and see how others are being infected, by observing the reproduction rate and the spectrum of disease.
“It’s a 26 country laboratory, where there is a chance of much better understanding of the dynamics of the outbreak and the spectrum of the disease in people who are infected.“It’s a 26 country laboratory, where there is a chance of much better understanding of the dynamics of the outbreak and the spectrum of the disease in people who are infected.
“What helps in an outbreak is to know what you don’t know,” he added.“What helps in an outbreak is to know what you don’t know,” he added.
“The evidence will come, as the rate of transmission and reproductive rates are estimates, not models. Models are only as good as the information in them.”“The evidence will come, as the rate of transmission and reproductive rates are estimates, not models. Models are only as good as the information in them.”
The number of people that each infected person will go on to infect has been estimated at between 2.6 and 2.68.The number of people that each infected person will go on to infect has been estimated at between 2.6 and 2.68.
Heymann, now professor of infectious disease epidemiology at the London School of Hygiene and Tropical Medicine, said: “The risk factors include the transmission ability, reflected in the reproductive number, but also how it is infected, ie body secretions, not washing your hands, or face to face, like sneezing.”Heymann, now professor of infectious disease epidemiology at the London School of Hygiene and Tropical Medicine, said: “The risk factors include the transmission ability, reflected in the reproductive number, but also how it is infected, ie body secretions, not washing your hands, or face to face, like sneezing.”
As late as last week, Chinese officials were only looking at severe cases of the virus. Now, attention is turning to less severe cases and what that means, Heymann said. “Each gives a different picture,” he said. “As more and more information becomes available, the models will be refined.”As late as last week, Chinese officials were only looking at severe cases of the virus. Now, attention is turning to less severe cases and what that means, Heymann said. “Each gives a different picture,” he said. “As more and more information becomes available, the models will be refined.”
Some experts have predicted outbreak epicentres elsewhere. Gabriel Leung and colleagues from the University of Hong Kong published the results of their model in the Lancet a few days ago, estimating 75,000 cases at the end of January.Some experts have predicted outbreak epicentres elsewhere. Gabriel Leung and colleagues from the University of Hong Kong published the results of their model in the Lancet a few days ago, estimating 75,000 cases at the end of January.
Like others, they identified a time lag of about one to two weeks while estimating a doubling in number of infections every six days or so.Like others, they identified a time lag of about one to two weeks while estimating a doubling in number of infections every six days or so.
Leung warned that other “large cities overseas with close transport links to China could also become outbreak epicentres, unless substantial public health interventions at both the population and personal levels are implemented immediately.”Leung warned that other “large cities overseas with close transport links to China could also become outbreak epicentres, unless substantial public health interventions at both the population and personal levels are implemented immediately.”