#14,731
We continue to see a doubling of confirmed novel coronavirus cases roughly every 48 hours, which means - as the tweet shown above by Sharon Sanders of FluTrackers - we will almost certainly exceed the confirmed number MERS-CoV cases since 2012 (n=2499) sometime tomorrow.
Although the numbers are literally changing by the hours, the latest daily compilation of case counts from around the world by Sharon (see FluTrackers 2019-nCov Confirmed Case List by Country w/Links to Sources) finds 2017 total confirmed cases and 56 deaths as of this evening.
Australia: 4 cases link
Canada: 1 link
China: 1975 cases & 56 deaths link (from the report dated 26/1/20)
France: 3 cases link
Hong Kong: 5 cases link and link and link
Japan: 3 cases link
Macau: 2 cases link and link
Malaysia: 3 cases link
Nepal: 1 case link
Singapore: 4 cases link
South Korea: 3 cases link
Taiwan: Taiwan citizen returned from Wuhan - 3 case link
Thailand: 6 cases link
United States: 2 cases link
Vietnam: 2 cases link
Last edited by sharon sanders; Today, 10:16 PM.
This rapid growth has fostered a number of preliminary estimates of how well this novel coronavirus is transmitting among humans (see here, here, and here).
The yardstick by which disease transmissibility is measured is its R0 (pronounced R-nought) or Basic Reproductive Number. Essentially, the number of new cases in a susceptible population likely to arise from a single infection.
In the simplest of terms, with an R0 below 1.0, a virus (as an outbreak) begins to sputter and dies out. Above 1.0, and an outbreak can have `legs’.
Calculating the R0 is notoriously difficult, particularly since much hinges upon the existence and subtle differences between viral strains, the accuracy of surveillance and reporting, `seasonality’, and individual host responses to the virus (i.e. number of `super spreaders’).
Like the CFR (Case Fatality Ratio), the R0 can vary considerably over time or geography, often ends up being described as a `range’, and usually isn’t well established (or at least, generally agreed upon) until long after an outbreak has ended.
Like the CFR (Case Fatality Ratio), the R0 can vary considerably over time or geography, often ends up being described as a `range’, and usually isn’t well established (or at least, generally agreed upon) until long after an outbreak has ended.
The researchers at the MRC Centre for Global Infectious Disease Analysis at Imperial College London have released their 3rd report, which estimates the virus has a healthy average R0 of 2.6 (range 1.5-3.5).
The authors close the full report (PDF) with this cautionary note:
Report 3: Transmissibility of 2019-nCoV (Download Report 3)
Natsuko Imai, Anne Cori, Ilaria Dorigatti, Marc Baguelin, Christl A. Donnelly, Steven Riley, Neil M. Ferguson
WHO Collaborating Centre for Infectious Disease Modelling, MRC Centre for Global Infectious Disease Analysis, J-IDEA, Imperial College London, UK
Correspondence: neil.ferguson@imperial.ac.uk
Note: This is an extended version of an analysis previously shared with WHO, governments and academic networks between 22/1/20-24/1/20
Summary Report 3
Self-sustaining human-to-human transmission of the novel coronavirus (2019-nCov) is the only plausible explanation of the scale of the outbreak in Wuhan. We estimate that, on average, each case infected 2.6 (uncertainty range: 1.5-3.5) other people up to 18th January 2020, based on an analysis combining our past estimates of the size of the outbreak in Wuhan with computational modelling of potential epidemic trajectories.
This implies that control measures need to block well over 60% of transmission to be effective in controlling the outbreak. It is likely, based on the experience of SARS and MERS-CoV, that the number of secondary cases caused by a case of 2019-nCoV is highly variable – with many cases causing no secondary infections, and a few causing many. Whether transmission is continuing at the same rate currently depends on the effectiveness of current control measures implemented in China and the extent to which the populations of affected areas have adopted risk-reducing behaviours.
In the absence of antiviral drugs or vaccines, control relies upon the prompt detection and isolation of symptomatic cases. It is unclear at the current time whether this outbreak can be contained within China; uncertainties include the severity spectrum of the disease caused by this virus and whether cases with relatively mild symptoms are able to transmit the virus efficiently. Identification and testing of potential cases need to be as extensive as is permitted by healthcare and diagnostic testing capacity – including the identification, testing and isolation of suspected cases with only mild to moderate disease (e.g. influenza-like illness), when logistically feasible.
The authors close the full report (PDF) with this cautionary note:
Despite the recent decision of the WHO Emergency Committee to not declare this a Public Health Emergency of International Concern at this time, this epidemic represents a clear and ongoing global health threat. It is uncertain at the current time whether it is possible to contain the continuing epidemic within China. In addition to monitoring how the epidemic evolves, it is critical that the magnitude of the threat is better understood. Currently, we have only a limited understanding of the spectrum of severity of symptoms that infection with this virus causes, and no reliable estimates of the case fatality ratio – the proportion of cases who will die as a result of the disease. Characterising the severity spectrum, and how severity of symptoms relates to infectiousness, will be critical to evaluating the feasibility of control and the likely public health impact of this epidemic.
