The central government has designated all the major metro cities – Delhi, Mumbai, Chennai, Kolkata, Hyderabad, Bengaluru and Ahmedabad – as red zones in a revised list shared on Thursday.

The categorisation in red zone is the most stringent, and is comprised of containment zones.

According to Centre’s guidelines, districts with high load of coronavirus cases or which have a high growth rate of the disease are classified under red zones, while those with considerably fewer cases of the respiratory infection fall in orange zones.

Districts with no coronavirus cases are categorised as green zones.

The Centre has said that necessary action should be initiated in red zones as part of containment action plan, which includes stringent perimetre control, active search for cases, testing of all cases, contact tracing and clinical management of all confirmed cases.

“It is critical to ensure that necessary action for containment so as to break the chain of teansmission of virus is initiated in both red and orange zone districts reporting confirmed cases,” the order from Union health ministry said.

In urban districts, containment zones will be demarcated on the basis of residential colony, mohallas, municipal wards, police-station area, municipal zones, or towns. In rural areas, these zones will be based on villages, clusters of villages, gram panchayats, among others, the health ministry order said.

There are 130 red zones, 284 orange zones and 319 green zones across the country, as per the revised list released by the Centre.

Uttar Pradesh and Maharashtra have the highest number of red zones at 19 and 14 respectively, followed by Tamil Nadu at 12. All 11 districts of Delhi have also been marked as red zones.

In fact, the National Capital Region (NCR) has a large number of hostpots or ‘red zones’. These include Faridabad, Sonipat, and Noida (Gautam Buddh Nagar).