Explained: What is community transmission of Covid-19, the phase Delhi health minister hinted city has hit?
Delhi Health Minister Satyendar Jain said the source of infection was not known in half the coronavirus cases in the city, adding it was up to the Centre to declare whether the community transmission stage had been reached.
A woman looks out of a window at a mall in New Delhi. (Express photo: Tashi Tobgyal)
Delhi Health Minister Satyendar Jain Tuesday said the source of Covid-19 infection in 50 per cent of the cases in the national capital was unknown, adding that it was up to the Centre to declare whether the city had entered the community transmission phase.
The health minister also indicated that the assessment of the local administration points towards the “third stage of spread”. “Director AIIMS Randeep Guleria has said (there has been community transmission) but Centre has not yet confirmed it,” Jain said.
“There are many cases where sources are not known. But we can say that [community transmission] officially only if the Centre admits it. In epidemiology, community spread happens to be the third stage,” he added.
Explained: What is community transmission?
According to the World Health Organisation (WHO), community transmission “is evidenced by the inability to relate confirmed cases through chains of transmission for a large number of cases, or by increasing positive tests through sentinel samples (routine systematic testing of respiratory samples from established laboratories)”.
In other words, community transmission or spread is said to be taking place when the source of the contagion is not known, i.e. when one is unable to trace an infection back to a carrier who has travelled in an affected area, or through contact with a person who has the disease.
A state of community spread implies that the virus is now circulating in the community, and can infect people with no history — either of travel to or contact with affected people and areas. At this stage, it is theoretically possible for everyone to catch the infection.
Has community transmission stage arrived in India?
The government has so far maintained that there is no community transmission in the country.
Some experts, however, have disagreed with this assertion for months, and said that community transmission of coronavirus is already taking place, and is not getting detected because India is not testing enough people.
In the last week of May, a joint statement by Indian Public Health Association, Indian Association of Preventive and Social Medicine and Indian Association of Epidemiologists read, “It is unrealistic to expect that COVID-19 pandemic can be eliminated at this stage given that community transmission is already well-established across large sections or sub-populations in the country.”
What are the stages of a pandemic?
In the first stage of a disease that eventually takes the form of a pandemic sweeping the globe, cases are imported into a country in which the infection did not originate. An infection whose spread is contained within the boundaries of one or some countries is obviously not a pandemic. The first case of Covid-19 outside China was reported in Thailand.
The second stage is when the virus starts being transmitted locally. Local transmission means that the source of the infection is from within a particular area and the trajectory the virus has taken from one person to the next is clearly established.
The third stage is that of community transmission.
There is also a fourth stage in every pandemic. It is when the disease, Covid-19 in this case, becomes endemic in some countries. The Indian government’s containment plan takes this possibility into account.
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Among diseases that are currently endemic in India — meaning they occur round the year across the country — are malaria and dengue.
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