Friday, February 14, 2020

Comparing Coronavirus to SARS

A new interactive map from the London School of Hygiene & Tropical Medicine London School allows you to compare how Covid-19 compares to previous virulent epidemics. The Covid 2019 Tracker map visualizes the spread of Covid-19 around the world and allows you to compare this outbreak with the 2003 SARS, 2014 Ebola and 2009 Swine Flu epidemics.

The Covid-2019 Tracker map helps to visualize how virulent the Covid-19 really is. It shows how Coronavirus has already affected more countries than Ebola and has killed more people than SARS. However the map and the 'Summary' data also shows that so far Covid-19 has proved far less fatal than Ebola and has affected far fewer countries than Swine Flu.

The data on the Covid-2019 Tracker map is being updated daily based on information from the World Health Organisation.

Non-Normalized Data

Like every other Coronavirus tracking map that I have seen the Covid 2019 Tracker map does not normalize its data. This means that the circular markers on the map show the total number of Covid-19 cases and not the incidence rate of the virus in each country. This can be misleading. For example, at the moment the markers for Italy and India are the same size on the map because both Italy and India have had three cases of Covid-19. This is despite the fact that Italy is a far smaller geographical area than India and has a much smaller population. Italy has had 3 cases in a population of 62 million compared to India which has had 3 cases in a population of 1.28 billion. Obviously at the moment the incidence rate of Covid-19 is far lower in India than it is in Italy. However the Covid 2019 Tracker map uses the same sized markers for each country.

Data Collection Methods

The Covid 2019 Tracker, and the other maps which show the spread of the virus over time, are also prone to errors from changes to the way that the virus is being monitored and recorded. Just today China's National Health Commission removed 108 deaths from the overall total, because of a previous double counting of fatalities. At the same time the overall number of deaths and overall number of cases was also revised upwards as yesterday China changed its methodology for registering Covid-19 cases. You therefore need to take into account these methodological changes when trying to track the progression of the virus over time. None of the maps I have seen acknowledge these changes in how the virus is being recorded in their timelines or graphs showing the spread of the virus.

John Hopkins' Wuhan Coronavirus (2019-nCoV) Global Cases visualization was the first interactive map showing the spread of Covid-19. When I first reported on the map on the 23rd January the map reported 17 deaths and 555 total cases of the virus. Today the map is reporting 1,384 deaths and 64,447 total cases in 28 countries around the world.

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