Density of population has a direct association with the number of COVID-19 positive cases. The chances of infection spreading are greater in densely populated areas. But, a place can have dense population, yet people can isolate, work remotely and practice social distancing. Density of population becomes a risk factor for spread of infection where people live in close confined spaces and therefore are in close contact with one another. Social distancing becomes more difficult or practically impossible in such places.

In India, in states with average population density of 1185/sq km, average number of cases were 2048.

These, when compared to states with population density of 909/sq km, the number of cases were 34.6.

If these two sates (Chandigarh and Pondicherry) with high population density were taken out, the Average Density of other states were 217 and the average number of cases were 35. 

This shows that high density states have larger number of cases and low density states have significantly less number of cases. The exceptions are Chandigarh and Pondicherry which shows disciplined social distancing in high density states can make a difference.

“Cruise ships are examples of dense mixing of many persons in a confined space over a relatively long period. The density of the group of people on board the COVID-19-infected Diamond Princess, quarantined in Yokohama earlier this year, was estimated around four times higher than that in Wuhan, as was also the R0 before the onset of countermeasures” (J Travel Med. 2020 Mar 29).

The 40-day lockdown, has been extended for two weeks till 17th May. The districts have been categorized into Red (hotspot), Green and Orange Zones based on their risk profiling.

Green Zones will be districts with either zero confirmed cases till date, or no confirmed case in the last 21 days, while districts will be placed in Red Zones depending on the total number of active cases, doubling rate of confirmed cases, extent of testing and surveillance feedback from the districts.

All metros and major cities in the country have been placed in the Red Zone (hotspots).

Population density according to the 2011 census of India:

Delhi: 11,312/sq km

Kolkata: 24,252/sq km 

Chennai: 26,903/sq km

Mumbai: 20,482/sq km

Hyderabad: 10,477/sq km

Indore: 25,170/sq km

Lucknow: 1,815/sq km

Surat: 14,000/sq km 

Ahmedabad: 12,000/sq km

Jaipur: 6500/sq km

Chandigarh:  9252/sq km

Green Zone

Goa: 394/sq km

Arunachal Pradesh: 17/sq km

Manipur: 122/sq km

Thirty out of 33 districts in Assam are in the green zone; no red zone. The population density in Assam is 397/sq km. Puducherry has a population density of about 2547/sq km; three out of 4 districts are green zones; there is no red zone.

Number of cases linked to population density in India: Migrant decongestion is the answer

In print: IJCP May Issue

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA