Epidemics in India: Causes, Patterns and Control

• An epidemic is the occurrence of a disease in a community or region clearly above the number normally expected for that place and time.
• It is a biological hazard: it spreads through people, vectors, water or food, and its map follows climate, settlement, mobility and poverty.
• India’s dense cities, monsoon breeding conditions and uneven sanitation and health services make it highly exposed.

Concepts

Scale of disease occurrence

• Sporadic: scattered cases with no clear link between them.
• Endemic: a disease constantly present at a usual level in an area, such as malaria in tribal forest tracts of Odisha.
• Outbreak: a sudden rise confined to a limited locality.
• Epidemic: a marked excess over the expected level across a community or region.
• Pandemic: an epidemic that crosses continents, such as COVID-19.

The epidemiological triad

• Disease results from the interaction of agent, host and environment.
  • Agent: virus, bacterium or parasite.
  • Host: age, nutrition, immunity, occupation.
  • Environment: temperature, humidity, stagnant water, crowding, sanitation.
• The geographer’s concern is the environment and the spatial pattern: where a disease occurs, how it diffuses and who is exposed.

How disease diffuses

• Contagious diffusion: spread through direct contact to nearby people, so it weakens with distance.
• Hierarchical diffusion: a jump along transport links from metropolis to city to town.
  • COVID-19 entered through international travel and moved outward from major urban centres.
• Relocation diffusion: carried by migrants to new areas.
• The ideas draw on the spatial diffusion work of Torsten Hägerstrand.

Causes and Geographical Factors

• Climate: warm, humid conditions and monsoon pools favour mosquitoes; transmission of many vector-borne diseases peaks during and after the rains.
• Floods and disasters: contaminated water and broken sewers bring cholera, diarrhoea and leptospirosis.
• Urbanisation: slums, water stored in containers and construction sites favour Aedes mosquitoes, the vector of dengue and chikungunya.
• Irrigation and land-use change: canals and paddy fields extend vector habitat; Japanese encephalitis is tied to paddy and pig rearing.
• Forest disturbance: closer contact between people and wildlife raises zoonotic spillover; Nipah is carried by fruit bats.
• Mobility: migrant labour and rapid transport shorten the distance between regions.
• Poverty: undernutrition and weak health services raise both infection and death.
• Climate change: warmer conditions can extend vectors to higher altitudes and new seasons.

Major Epidemics and Regional Patterns

Chikungunya

• The name of this viral disease comes from a Makonde word for ‘that which bends up’, after the stooped posture its joint pain causes.
• It was recorded in Kolkata in 1963 and at Barsi in Maharashtra in 1973, then stayed quiet for 32 years.
• It re-emerged in 2005–06, starting in Andhra Pradesh, Karnataka and Maharashtra and reaching about 16 States, with almost 1.3 million suspected cases in 2006.
• Regional pattern: the belt of Karnataka, Maharashtra, Andhra Pradesh and Tamil Nadu, and later Kerala, reflecting water storage, seasonal rain and urban growth.
• A low-immunity population after a long gap allowed the rapid spread.

Nipah

• Nipah is a zoonotic viral encephalitis with a high fatality rate.
• India’s early outbreaks were at Siliguri (2001; 66 cases, 45 deaths) and Nadia (2007; 5 cases, 5 deaths) in West Bengal.
• Kozhikode and Malappuram, Kerala (2018): 19 cases and 17 deaths. Later events occurred in Kerala in 2019, 2021, 2023 and 2025.
• Socio-spatial consequences:
  • fear and social stigma against patients, families and health workers;
  • local fall in fruit sales, tourism and movement, and closure of public gatherings;
  • hospital-centred spread, with nurses and carers at risk;
  • containment zones reorganised daily life at the ward level.
• Fast contact tracing and isolation confined the outbreaks to small areas.

COVID-19

• India’s first case was reported in Thrissur, Kerala, in January 2020.
• Urban slums were vulnerable because of high density, shared toilets and water points, and informal work.
  • Dharavi, Mumbai became the best-known example of this risk and of intensive local containment.
• The 2020 lockdown set off a large reverse migration of workers towards Uttar Pradesh, Bihar and other source States.
• The second wave of 2021 showed uneven hospital and oxygen capacity between regions.

Historical epidemics

• Influenza of 1918: a main cause of the fall in India’s population in the 1911–21 decade.
• Plague at Surat (1994): an outbreak followed by flight of residents and heavy economic loss.
• Muzaffarpur (2019): acute encephalitis deaths among children, linked with undernutrition and heat.

Consequences

• Demographic: deaths and illness, sharper among the poor, the old and the undernourished.
• Economic: lost work, household medical debt, and disruption of trade, tourism and supply chains.
• Social: stigma, school closure, and reverse migration.
• Spatial: containment zones, deserted markets and pressure on metropolitan hospitals.

Control and Management

• Law: the Epidemic Diseases Act, 1897, and the Disaster Management Act, 2005, used for COVID-19.
• Surveillance: the Integrated Disease Surveillance Programme, with weekly reporting from districts.
• Vector control: the National Centre for Vector Borne Diseases Control runs insecticide-treated nets, spraying, and removal of breeding sites.
• Malaria: India aims at zero indigenous cases by 2027 and elimination by 2030. India left WHO’s ‘high burden, high impact’ group in 2024.
• One Health: joint human, animal and environmental surveillance, especially for zoonoses.
• GIS mapping: hot spots, risk zones and service gaps can be mapped for targeted action.
• Basic services: safe water, sanitation, housing and primary health care remain the lasting answer.