Emerging Infections Surveillance
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Direct answer
Nipah virus reached Kozhikode district, Kerala, in May 2018 and killed seventeen of the eighteen people it infected — a textbook emerging infection: a bat virus, a new geography, explosive severity and hospital amplification. Emerging infections are those newly appearing or rising in incidence, range or virulence, driven by deforestation, urbanisation, livestock intensification, travel and climate; re-emerging ones — dengue, scrub typhus, drug-resistant tuberculosis — resurge on weakened systems. India's surveillance answer runs from the Integrated Disease Surveillance Programme to its real-time successor IHIP under the National Centre for Disease Control, while the International Health Regulations (2005) frame the global alert machinery of PHEIC declarations.
What you must remember
- Nipah virus: Pteropus medius fruit bats are the reservoir; Kerala outbreaks in 2018, 2019, 2021 and 2023 after Siliguri in 2001, with person-to-person spread in families and hospitals; case fatality has exceeded two-thirds; ribavirin has been used and the m102.4 monoclonal antibody is held for compassionate use.
- Zika virus: Aedes-borne; Indian outbreaks include Ahmedabad (2016-17) and Jaipur (2018, over a hundred confirmed cases); microcephaly and Guillain-Barre syndrome are the complications; diagnosis by RT-PCR on serum and urine.
- Kyasanur forest disease: "monkey fever", recognised in 1957 in Karnataka's Shimoga forests; transmitted by the Haemaphysalis spinigera tick, with langur and bonnet macaque deaths acting as sentinels; a formalin-inactivated vaccine covers endemic districts; the illness is biphasic with haemorrhage.
- Crimean-Congo haemorrhagic fever: first recognised in India in 2011 at Sanand, Gujarat; Hyalomma anatolicum ticks and livestock maintain it; notorious for nosocomial spread; ribavirin is the specific therapy.
- Chandipura virus: explosive paediatric encephalitis with high mortality, classically sandfly-associated in central and western India; Gujarat's 2024 outbreak refocused attention on it.
- The COVID lesson institutionalised: INSACOG, the Indian SARS-CoV-2 Genomics Consortium set up in December 2020, tracked the Delta variant (B.1.617.2), declared a variant of concern on 11 May 2021 — the standing case for genomic surveillance.
- Surveillance architecture: indicator-based reporting (syndromic, clinical, laboratory-confirmed tiers) plus event-based surveillance (media scanning, rumour registers, hotlines); IDSP, launched 2004, evolved into IHIP in 2021 — a case-based, near-real-time platform reaching village level.
- IHR 2005: legally binding, it mandates core capacities and empowers the WHO Director-General to declare a Public Health Emergency of International Concern — declared for H1N1 (2009), polio (2014), Ebola (2014 and 2018-20), Zika (2016), COVID-19 (2020) and mpox (2022, and again in 2024 over clade Ib).
Kerala's 2018 Nipah response as a template
An index cluster from Perambra, in Kozhikode district, entered a private hospital in May 2018. First, verify the diagnosis: Nipah was confirmed at the National Institute of Virology, Pune, from samples of unexplained encephalitis. Second, isolate and trace: contacts were listed, home-quarantined through the incubation period (usually 4-14 days) and monitored twice daily — over two thousand. Third, find the source: Pteropus bat colonies near the index household tested positive, closing the zoonotic loop. Fourth, break hospital amplification: contact and droplet precautions, dedicated isolation wards, restricted visiting — the chain had already spread within family and ward. Fifth, communicate: daily government briefings kept the public ahead of rumour. The episode closed with eighteen cases and seventeen deaths; the 2021 and 2023 recurrences, met with the same template, stayed in single digits.
Where students slip: high fatality is not high transmissibility
Case fatality and epidemic potential are different axes, and conflating them costs marks. Nipah kills most of those it infects, yet its reproduction number hovers near or below one — chains burn out with isolation, contact tracing and nursing discipline. SARS-CoV-2's Delta variant, far less lethal, spread with an effective reproduction number estimated around five in unprotected populations because it transmitted from presymptomatic and asymptomatic people. Read every agent on both axes: what spreads silently (SARS-CoV-2, dengue) needs case-based digital reporting and genomics; what kills loudly (Nipah, Crimean-Congo haemorrhagic fever) needs hospital infection control and contact tracing.
Frequently asked questions
Which bat species maintains Nipah virus in India?
Pteropus medius (formerly P. giganteus), the Indian flying fox; the virus was detected in bats around the index household at Perambra during the 2018 Kozhikode outbreak.
What is IHIP?
India's near-real-time, case-based successor to the IDSP launched in 2021, reporting down to village level with analytic dashboards, under the National Centre for Disease Control.
Which tick transmits Kyasanur forest disease?
Haemaphysalis spinigera; monkey die-offs in endemic Karnataka precede human cases and trigger vector control and vaccination drives.
What is a PHEIC, and what triggers it?
A Public Health Emergency of International Concern, declared by the WHO Director-General under the IHR 2005 when an event is serious, unusual or unexpected, risks cross-border spread and requires coordinated international response — most recently for COVID-19 and mpox.
Where was India's first Crimean-Congo haemorrhagic fever outbreak?
Sanand, Gujarat, in 2011 — Hyalomma ticks from livestock; health workers were infected nosocomially, and ribavirin remains the specific treatment.
What is event-based surveillance?
Rapid capture and verification of unstructured early signals — media reports, rumour registers, hotline alerts — investigated alongside indicator-based routine reporting as the early-warning tier of IDSP-IHIP.