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.
“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’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.
What is the virus causing illness in Wuhan?
It is a member of the coronavirus family that has never been encountered before. Like other coronaviruses, it has come from animals. Many of those initially infected either worked or frequently shopped in the Huanan seafood wholesale market in the centre of the Chinese city.
What other coronaviruses have there been?
New and troubling viruses usually originate in animal hosts. Ebola and flu are other examples – severe acute respiratory syndrome (Sars) and Middle Eastern respiratory syndrome (Mers) are both caused by coronaviruses that came from animals.
What are the symptoms of the Wuhan coronavirus?
The virus causes pneumonia. Those who have fallen ill are reported to suffer coughs, fever and breathing difficulties. In severe cases there can be organ failure. As this is viral pneumonia, antibiotics are of no use. The antiviral drugs we have against flu will not work. If people are admitted to hospital, they may get support for their lungs and other organs as well as fluids. Recovery will depend on the strength of their immune system. Many of those who have died were already in poor health.
Is the virus being transmitted from one person to another?
Human to human transmission has been confirmed by China’s national health commission, and there have been human-to-human transmissions in the US and in Germany. As of 8 February, the death toll stands at 722 inside China, one in Hong Kong and one in the Philippines. Infections inside China stand at 31,161 and global infections have passed 280 in 28 countries. The mortality rate is 2%.
Two members of one family have been confirmed to have the virus in the UK, and a third person was diagnosed with it in Brighton, after more than 400 were tested and found negative. The Foreign Office has urged UK citizens to leave China if they can. Five new cases in France are British nationals, and British nationals are also among the 64 cases on a cruise liner off Japan.
The number of people to have contracted the virus could be far higher, as people with mild symptoms may not have been detected. Modelling by World Health Organization (WHO) experts at Imperial College London suggests there could be as many as 100,000 cases, with uncertainty putting the margins between 30,000 and 200,000.
Why is this worse than normal influenza, and how worried are the experts?
We don’t yet know how dangerous the new coronavirus is, and we won’t know until more data comes in. The mortality rate is around 2%. However, this is likely to be an overestimate since many more people are likely to have been infected by the virus but not suffered severe enough symptoms to attend hospital, and so have not been counted. For comparison, seasonal flu typically has a mortality rate below 1% and is thought to cause about 400,000 deaths each year globally. Sars had a death rate of more than 10%.
Should I go to the doctor if I have a cough?
Unless you have recently travelled to China or been in contact with someone infected with the virus, then you should treat any cough or cold symptoms as normal. The NHS advises that people should call 111 instead of visiting the GP’s surgery as there is a risk they may infect others.
Is this a pandemic and should we panic?
Health experts are starting to say it could become a pandemic, but right now it falls short of what the WHO would consider to be one. A pandemic, in WHO terms, is “the worldwide spread of a disease”. Coronavirus cases have been confirmed in about 25 countries outside China, but by no means in all 195 on the WHO’s list.
There is no need to panic. The spread of the virus outside China is worrying but not an unexpected development. The WHO has declared the outbreak to be a public health emergency of international concern, and says there is a “window of opportunity” to halt the spread of the disease. The key issues are how transmissible this new coronavirus is between people and what proportion become severely ill and end up in hospital. Often viruses that spread easily tend to have a milder impact.
Sarah Boseley Health editor and Hannah Devlin
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.”
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.
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.”
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.
“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.
“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.
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.”
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.
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.”
