When and How Should We Ease Mitigation Measures

Lancet is a well-regarded British medical journal.  A group of researchers from Hong Kong have published an article in the journal on whether or not and how extreme mitigation spread measures should be relaxed.  The article was published on April 8th and based on data from areas of China outside of Wuhan and Hubei as of March 18th, so not the most current information, but China obviously was much further along in the initial phase of the epidemic, since it was the origin of the virus.   (Lancet Article)   The authors described the very severe lockdown put in place in China and the effect that lockdown had on spread, and suggest that relaxing the lockdown too quickly would lead to a resurgence, primarily because herd immunity has not developed.  The resurgence would be caused by infections from people traveling into China and some residual virus seeding.

They had sufficient data to estimate transmissibility of the virus in four major Chinese cities and to study the effect of the lockdowns on that rate of transmission.  They conducted other analyses on other geographic areas.  Their primary output was a model that explored what would happen if severe mitigation measures were relaxed.  They found that the extreme measures did drive transmissibility below 1, but that when the measures are relaxed, transmissibility would return to above 1.  Of the four cities, only one had transmissibility rates that in actuality reached as high as 2.5 and most had rates that were only briefly above 1, probably due to the fact that the lockdown went into place in these areas shortly after the first cases had been reported.  They estimate a case fatality rate of around .98%, but given the lack of data about the real number of infections, that is pretty much speculation.  They interpreted their model output to mean that mitigation measures should be relaxed very slowly, to avoid transmissibility rising above 1 and cases growing very rapidly.  Continual testing and contact tracing would be critical, in their view, to monitor any change in transmissibility rate.  And they noted how social media and online commercial platforms could be used to track activity and social mixing.

It isn’t these researchers fault, but the infection and death rates they were basing their analysis on are unquestionably unreliable and too low.  The Chinese government has shown every willingness to mislead and lie about the nature of the epidemic in China.  It is true, however, that how mitigation measures are relaxed will have an impact on the rate of new infections and disease.  But the economic effects need to be considered as well.  I am convinced that China began relaxing its lockdown, not just because transmission may have fallen, but because the country realized it simply could not sustain an extended lockdown.