15 April 2020

COVID-19 Epidemiology, Part 5

COVID-19 Epidemiology, Part 5

(All my data are from the government site: Coronavirus (COVID-19) cases in the UK ; Last updated 14 Apr 2020, 3:44 pm GMT.)

     The news for the United Kingdom of GB continues to be mildly good. The 'doubling-time', measured in days, which is my chosen index of the spread of the virus through the population, was steady at 3.5 - 4 for the 13 days prior to the 24th March (see Fig. 1). 
     On the 24th March the government instigated what we call 'Lockdown' which closed schools, and many shops, cancelled many trains and busses, instituted restricted numbers inside food-shops, and many other curtailments. 
     It took some time for the public to get behind these restriction, but they are now very widely observed. Since the 24th of March the doubling-time of the total case-count has started to climb, and now climbs persistently. (See Fig. 1) On 14th April the doubling time was 12 days. 

Fig. 1  depicts the un-smoothed data as the increment in the total case-count, converted to 'doubling-time' in days. The horizontal axis is 'days' before and after 31st March

     Another very good measure of success in curbing the spread of this (or any other virus), discussed by Professor Trisha Greenhalgh and Jeremy Howard (1), is the transmission rate, i.e. the number of new infections generated by an infected person. If that number is greater than 1.0 the virus spreads; if less than 1.0 the epidemic dies out. COVID-19  started out with a transmission rate of 2.4. The paper by Greenhalgh and Howard (1) goes on to show how masks reduced the COVID-19 transmission rate in several countries. 


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