More than 81,000 coronavirus cases have now been reported globally as the death toll passes 2,700, with a spike in cases confirmed in South Korea, Italy, Japan and Iran this week, as well as a hotel in Tenerife being put on lockdown. As the World Health Organisation (WHO) warns countries should be “in a phase of preparedness” for a pandemic, scientists in China have made a worrying breakthrough. Researchers confirmed a 20-year-old woman in Wuhan – the epicentre of the disease – passed the virus to five of her family members, but never got sick herself.
The case study is the first concrete evidence that a person showing no symptoms can pass the coronavirus to others – a fact that could make curbing the outbreak even more challenging as those infected become near-impossible to identify.
Researchers said the woman was isolated and closely observed at the Fifth People’s Hospital of Anyang, where she never become physically ill, even after her family members developed fevers, two of them got severe pneumonia.
For now, the woman’s asymptomatic transmission appears to be an anomaly, but health experts have documented other instances in which people tested positive for the virus without showing symptoms.
A report from the Chinese Centre for Disease Control and Prevention analysed records of all of China’s reported cases of the virus from December 8 to February 11 and found that 1.2 percent of patients were found to have no symptoms.
Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases said: “It’s very clear that the people who are getting caught in that umbrella of reporting are the people that present themselves to a hospital.
“There’s another whole cohort that is either asymptomatic or minimally symptomatic.”
A case of asymptomatic transmission similar to the one described in the new case study was previously identified in Germany, but that research turned out to be flawed.
According to a letter published in the New England Journal of Medicine, a woman from Shanghai transmitted the virus to a 33-year-old German businessman in January.
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Speaking to BBC Radio 4’s Today Programme, he warned: “The most important thing that we are realising is that it is very infectious but it is infectious if you’re close up with people.
“So, social distancing and learning how to not be very close to each other is really important.
“Secondly, if people are isolated and getting treatment, then it’s possible to slow the spread of the virus and actually to reduce the size of the outbreak when it does get established, so reacting quickly and effectively is extremely important.
“What the WHO is encouraging is a mindset to get ready for the arrival of this illness and to be prepared for the steps that have to be taken to do it effectively and together.”