27th March – Lockdown

Why lockdown is for 21 days?

Is there any public health/ epidemiological significance to the 21-day lockdown period announced by Prime Minister Narendra Modi to combat Coronavirus epidemic?

Background –

  • There are four common coronaviruses that cause mild to moderate upper-respiratory tract illnesses, like the common cold. These are – 229E (alpha coronavirus); NL63 (alpha coronavirus), OC43 (beta coronavirus); HKU1 (beta coronavirus).
  • While the two other human coronaviruses that have been known to frequently cause severe symptoms are – MERS-CoV (the beta coronavirus that causes Middle East Respiratory Syndrome, or MERS); SARS-CoV (the beta coronavirus that causes Severe Acute Respiratory Syndrome, or SARS).

Learning from the past –

  • 21-day quarantines have been discussed elaborately in the context of Ebola and the calculations are based on the estimated incubation period of the virus in a human host.
  • The 21-day quarantine value is derived from interpretations of outbreak data, past and present, public health experts said.
  • This being a new corona virus, they have estimated that the median incubation period (the time between the entry of virus to the onset of symptoms/ disease) falls within this period.

Scientific reasons –

  • In epidemiological terms, the logic is that we have arrived at an incubation period of 14 days. Give another week for the residual infection to die out, for the tail end, to be entirely safe, and you arrive at 21 days.
  • Science Daily recently reported of a new study in the journal Annals of Internal Medicine “that calculates that the median incubation period for COVID-19 is just over five days and that 97.5% of people who develop symptoms will do so within 11.5 days of infection.
  • Researchers headed by Nicholas Reich, Associate Professor in the School of Public Health and Home Sciences, University of Massachusetts, Amherst, reportedly examined 181 confirmed cases with identifiable exposure and symptom onset windows to estimate the incubation period of COVID-19. They conclude that ‘the current period of active monitoring recommended by the U.S. Centers for Disease Control and Prevention [14 days] is well supported by the evidence’.

How does lockdown help?

In the interim, the lockdown or quarantine also creates some breathing space — to convince people of the seriousness of the situation and build positive public opinion, carry out disinfection of all buildings, vehicles and surfaces, and allows hospitals to prepare themselves for the next phase of operations.

SourceThe Hindu

QUESTIONWhy did the Government of India lock down the country for 21 days exactly during the coronavirus outbreak? What is the relevance of these numbers?

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