The novel coronavirus epidemic could spread to around two-thirds of the world’s population if it cannot be controlled, according to Hong Kong’s leading public health epidemiologist.
His warning came after the head of the World Health Organisation (WHO) said recent cases of coronavirus patients who have never visited China could be the “tip of the iceberg”.
Professor Gabriel Leung, chair of Public Health Medicine at Hong Kong University, said the overriding question was to figure out the size and shape of the iceberg. Most experts thought that each person infected would go on to transmit the virus to around 2.5 other people. That gave an “attack rate” of 60-80%.
“Sixty per cent of the world’s population is an awfully big number,” Leung told the Guardian in London, en route to an expert meeting at the WHO in Geneva.
Even if the general fatality rate is as low as 1%, which Leung thinks is possible once milder cases are taken into account, the death toll would be massive.
He will tell the WHO expert meeting that the main issue is the scale of the growing worldwide epidemic and the second priority is to find out whether the drastic measures taken by China to prevent the spread have worked – because if so, other countries should think about adopting them.
Leung – one of the world’s experts on coronavirus epidemics, who played a major role in the Sars outbreak in 2002-2003 works closely with other leading scientists such as counterparts at Imperial College London and Oxford University.
At the end of January he warned in a paper in the Lancet that outbreaks were likely to be “growing exponentially” in cities in China, lagging just one to two weeks behind Wuhan. Elsewhere, independent self-sustaining outbreaks in major cities globally could become inevitable” because of the substantial movement of people who were infected but had not yet developed symptoms, and the absence of public health measures to stop the spread.
Epidemiologists and modellers were all trying to figure out what was likely to happen, said Leung. Is 60 to 80% of the world’s population going to get infected? Maybe not. Maybe this will come in waves. Maybe the virus is going to attenuate its lethality because it certainly doesn’t help it if it kills everybody in its path, because it will get killed as well, he said.
Experts also need to know whether the restrictions in the epicentre of Wuhan and other cities have reduced infections. Have these massive public health interventions, social distancing, and mobility restrictions worked in China? he asked. If so, how can we roll them out, or is it not possible?