The Indian Council of
Medical Research (ICMR) published research that compares the effectiveness and
feasibility of two approaches, attempting to contain an outbreak at the
border, and quarantining symptomatic cases within the country.
Details
Ø The research makes a case
for post-travel tracking rather than border containment. It uses mathematical
modelling to show that spending resources on quarantining symptomatic cases can
achieve a meaningful impact on the disease burden rather than attempting
to achieve infeasible levels of containment at the borders.
Ø It also accounts for the
inevitability that an outburst of cases would make lab confirmations
impractical. Therefore, the paper proposes “symptomatic surveillance” to be
included with quarantine measures.
Ø The government has focused
on random sampling of patients with severe symptoms and quarantining positive
cases. In the initial weeks of rising cases in India, asymptomatic travellers
were not tested.
Ø If India screened all
symptomatic airport arrivals from China, the epidemic would occur in 45 to 47.7
days. If all asymptomatic arrivals from China were screened, India would need
to identify at least 75% of asymptomatic infected arrivals in order to achieve
an “appreciable” delay in the outbreak. If 90% were identified, the delay would
be 20 days.
Ø There is no accurate, rapid
test to achieve the required detection levels, the paper notes, citing other
studies to show that thermal screening can miss at least 46% of infections.
Ø The only way to achieve the
needed detection levels, in fact, may be isolation of all arrivals from the
specified airports.
Ø The researchers built their
model with two scenarios. The optimistic scenario assumes that each infected
person transmits the virus to 1.5 other people (known as R0 or reproduction
number) and that asymptomatic infections do not infect others. The pessimistic
scenario assumes each infection transmits to four other people, and that
asymptomatic cases are half as infectious as symptomatic cases.
Ø The models show that once
community transmission occurs, the epidemic’s peak and duration can be greatly
affected by quarantining symptomatic cases, but only in the optimistic
scenario.
Ø The paper’s hypothetical
model found that quarantining 50% of symptomatic cases within three days of
their symptoms would reduce overall cases by 62% and the peak number of cases
by 89% in an optimistic scenario.
Ø The model assumes that
cases are only coming from certain regions in China, which is a major drawback.
We now know that many cases in India have actually come from the Middle East
and the UK.
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