The Union Health Ministry on Sunday listed parameters such as active COVID-19 cases, doubling and fatality rates and cases per lakh population, for the states and UTs to follow while categorising areas into red, orange or green zones.
It also issued guidelines for delineation of coronavirus containment and buffer zones and outlined the actions that have to be implemented in those areas to break the chain of transmission.
In a letter to the states and Union Territories, Health Secretary Preeti Sudan said states may categorise districts or municipal corporations into hotspots, red, orange and green zones.
They, however, may also choose to categorise sub-division, ward or any other appropriate administrative unit into the colour-coded zones after detailed analysis at their end, duly taking into consideration the geographical spread of cases, contacts and their zone of influence in terms of disease spread, the ministry said.
This comes after the Home Ministry issued guidelines for the fourth phase of the nationwide lockdown, giving power to the states and Union Territories to delineate red, green and orange zones as per the COVID-19 situation.
In her letter, Sudan said demarcation of the zones would be based on total active cases, cases per lakh population, doubling rate calculated over a seven-day period, case fatality rate, testing ratio (number of tests per lakh population) and sample positivity rate.
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The benchmarks or thresholds for critical and desirable levels for total
active cases would be more than 200 and zero or no reported case in the last 21 days respectively.
For active cases per lakh population, the critical threshold would be when more than 15, while for doubling rate calculated over a seven-day period, the critical level would be less than 14 days and desirable when more than 28 days.
As for case fatality rate, more than six per cent would be considered critical and less than one per cent desirable. The critical threshold for testing ratio (number of tests per lakh population) would be less than 65 while the desirable level would be more than 200, according to the letter.
Sample positivity rate would be considered critical if it's more than 6 per cent while less than 2 per cent is desirable.
The health ministry, however, underlined that the benchmarks or thresholds for critical and desirable levels are dynamic and may be revised by the Centre as per the evolving situation at the field level.
"The most important task once the zones are identified is field action in terms of implementation of containment plan of action. This entails identification of containment and buffer zones inside the red, orange and green zones from where cases have been primarily reported.
"A containment operation (large outbreak or cluster) is deemed successful when no case is reported in last 28 days from the containment zone," the letter stated.
According to the guidelines, the containment zones are delineated based on mapping of cases and contacts, geographical dispersion of cases and contacts, area having a well-demarcated perimeter and enforceability of perimeter control.
"It is reiterated that this is the primary area where intensive action is to carried out with the aim of breaking the chain of transmission," the letter stated.
Stringent action needs to be initiated within these containment zones in terms of an active search for cases through physical house-to-house surveillance by special teams formed for the purpose, testing of all cases as per sampling guidelines and contact tracing, identification of local community volunteers to help in surveillance, contact tracing and risk communication and strict enforcement of social distancing among others, it said.
The ministry also said a buffer zone has to be delineated around each containment zone and it shall be appropriately defined by the district administration or local urban bodies with technical inputs at the local level.
"Buffer zone will be primarily the area wherein additional and focused attention is needed so as to ensure that infection does not spread to adjoining areas. For effective containment, it is of paramount importance that the buffer is sufficiently large," the letter stated.
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