The coronavirus Covid-19 could reach its “peak” in a matter of days, research suggests.
Scientists from the London School of Hygiene & Tropical Medicine (LSHTM) predict if the virus carries on spreading as it has in the Chinese city Wuhan, the epicentre of the outbreak, it may peak in “mid-to-late February”.
While other experts are “hopeful” this will ring true, they stress no one can guarantee how Covid-19 will play out.
Since emerging at a seafood and live animal market at the end of last year, the virus has spread to at least 27 countries.
Authorities have confirmed more than 45,000 cases, of which 44,687 are in mainland China, according to John Hopkins University.
While most suffer flu-like symptoms, severe cases develop pneumonia, with the death toll exceeding 1,000 on Wednesday.
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To uncover how the outbreak may progress, the LSHTM scientists developed a mathematical model based on “international exported cases from Wuhan” and in the city itself.
They assumed the “chance of cases being exported” depended on the number in Wuhan, the number of outbound travellers before it “locked down” on 23 January and the “relative connectivity of different countries”.
Before travel restrictions were in place, the scientists estimate Covid-19’s reproduction number fluctuated between 1.5 and 4.5.
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This is the number of people an infected person goes onto infect.
A reproduction number of two would mean every patient is expected to pass the virus to two others.
If this “continues to vary as it has in Wuhan”, the scientists “project the outbreak would peak in mid-to-late February” as a result of “susceptibility declining to the point where transmission cannot be sustained”.
The scientists stress this has “substantial uncertainty”, with predictions improving in the “coming days” as more data emerges.
Speaking in response, Professor Rowland Kao – from the University of Edinburgh – said: “This is an analysis by an experienced and talented team, but as always limitations of the available data will affect predictions.
“The predictions for the outbreak peaking in Wuhan implies that, by whatever means, the number of new cases will start to decline – it does not imply the disease is necessarily under control.
“If previously unexposed populations become infected, the outbreak could start rising again.
“One thing to keep in mind is this is primarily based on data from Wuhan; the estimates for other countries are only for the import of cases, and thus worldwide estimates of decline are not made – they would likely contain substantially greater uncertainty.
He added: “In particular, in countries where no or few cases are reported, under-reporting may be a factor.
“Also, in areas where the infrastructure for detecting and controlling the disease is less well developed, the reproduction rate of the disease could be substantially influenced by non-biological factors, such as how effective quarantine strategies may be”.
Another expert was optimistic, but wary.
“I hope the peak of the outbreak in Wuhan is coming soon”, said Dr Robin Thompson from the University of Oxford.
“One proviso must be forecasting the peak of any outbreak is challenging, and so there is significant uncertainty in estimates of both the timing of the peak and the total number of cases that will occur.”
Dr Michael Head, from the University of Southampton, told Yahoo UK: “Modellers have to work with limited data to make predictions and are subject to continuous revision as the outbreak continues.
“Their estimates of a late-February peak, from a pragmatic perspective, are plausible.
“However, as the authors highlight, there are many caveats to their estimates that are reflective of the continuing uncertainties”.
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Covid-19’s reproduction number has been disputed.
Scientists from Imperial College London estimated each patient in China infected between 1.5 and 3.5 people up to January 18.
A team from the University of Oxford reported on 25 January if a patient were to arrive in the UK, there is more than a one-in-three chance they will pass Covid-19 on.
Based on data collected between 10 and 21 January, scientists from the Chinese University of Hong Kong estimated each patient could transmit the virus to between three and five people.
The number of patients has also been up for debate.
Scientists from the University of Hong Kong warned at the end of last month more than 75,000 people could have battled Covid-19 in Wuhan alone.
John Hopkins data shows confirmed cases in mainland China rose from 278 on 20 January to 4,400 a week later.
By 3 February it was 19,700, increasing to 34,100 on 7 February and 44,300 on 11 February.
Covid-19 has been compared to fellow coronavirus severe acute respiratory syndrome (Sars), which killed 774 people during its 2004 outbreak.
Scientists from Fudan University in Shanghai found Covid-19 appears to be 89.1% genetically similar to “a group of Sars-like coronaviruses”.
Although named Covid-19 by the World Health Organization (WHO), the International Committee on Taxonomy of Viruses is calling it “severe acute respiratory syndrome coronavirus 2” (SARS-CoV-2).
Authorities were famously tight-lipped about Sars, not informing the WHO until 11 February, when 305 cases - and five deaths - had occurred across six districts in Guangdong.
Nonetheless, Sars was brought under control in around eight months, with no cases being reported since.
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Most of the people who initially became unwell worked at, or visited, the Wuhan market.
While no one can say for sure where the virus came from, bats seem most likely.
The nocturnal creatures are thought to have been behind Sars and fellow coronavirus Middle Eastern respiratory syndrome (Mers), which killed 858 people during its 2012 outbreak.
Scientists from Peking University in Beijing suggested snakes may have been the “intermediate host” for Covid-19.
A team from South China Agricultural University have since found it could have “jumped” from bats to humans via pangolins.
Pneumonia occurs when a respiratory infection causes the alveoli (air sacs) in the lungs to become inflamed and filled with fluid or pus.
The lungs then struggle to draw in air, resulting in reduced oxygen in the bloodstream.
“Without treatment the end is inevitable,” said the charity Médecins Sans Frontières.
“Deaths occurs because of asphyxiation.”
The US Centers for Disease Control and Prevention has warned there is no specific treatment for coronaviruses.
Pneumonia is generally caused by bacteria, which tend to respond to antibiotics.
Professor Peter Horby, from the University of Oxford, claimed there is “no effective anti-viral” for Covid-19, with treatment being “supportive” while the immune system fights the virus.