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Intra-Country Spread of Corona Virus: Wo Index

We develop and use an Index Wo related to the R0 index used by epidemiologists to judge the progress made in controlling the spread of the Corona Virus within countries. The critical value of the Index is one. A value greater than one suggests that the Viral transmission is in its expansionary phase. A value lower than one indicates that the spread of the virus is slowing and is headed towards zero. There can and have been situations in which the virus went into a recessionary phase, but recovered and expanded in a second phase, before returning to the recessionary phase.

First, we examine the progress made in the four large democratic countries India, USA, Japan, and UK. Table 1 summarizes the Wo trends in India, USA, Japan, and UK, in terms of the latest value of the index for each country and the average of the index for the past one, two, three and four weeks. This puts the current index into perspective, so we can judge whether the current value is part of a trend, or merely a spike or temporary occurrence. All four countries have gone below one, the critical threshold of transmission. The USA with an index of 0.4 and UK with an index of 0.5 have made greater progress in slowing transmission of the Corona Virus than Japan (0.8) and India (0.9). With the index averaging less than 1 for the last two weeks and a clear down trend over the last four weeks, both USA and UK seem to be on the slow road to recovery. Japan has a more checkered history, with initial success followed with a reversal, with index averaging 1.06 during the 7 days ending April 17, 2020. India has just crossed the critical threshold from the expansionary to recessionary phase of the Corona Virus. Though the trend is clearly down in India, it is important to ensure that the trend is not reversed in the second half of April.

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