india

Updated: Aug 29, 2019 12:14 IST

Crimean-Congo haemorrhagic fever has killed three persons in Gujarat, which was the first state in the country where the zoonotic infection spread from livestock to humans was first confirmed in 2011.

Several wild and domesticated animals, such as cattle, sheep and goats, carry the virus without developing symptoms, which spreads to animal handlers, veterinarians, healthcare workers and the community through tick-bites and contact with infected animals, and from human-to-human through contact with the blood, secretions, bodily fluids of infected persons, or from contamination or poor sterilisation of medical equipment in sick rooms and hospitals.

In the absence of a vaccine, the virus kills around 30% of the people infected, usually in the second week of illness.

Earlier studies have found livestock infected with Crimean-Congo fever throughout India, but human outbreaks have been recorded mostly in Gujarat.

Between 2012 and 2015, Congo fever nosocomial infections in hospitals were reported in six districts of Gujarat (Ahmedabad, Amreli, Patan, Surendranagar, Kutch, and Aravalli), three districts of Rajasthan (Sirohi, Jodhpur, and Jaisalmer) and one in Uttar Pradesh.

A study to identify the high-risk population and areas in Gujarat tested 4,978 people from 33 districts in 2015, 2016 and 2017. Those tested included patients and their close contacts and neighbours, animal handlers, general population, farmers, abattoir workers, veterinarian and health workers. Twenty-five people tested positive. Infection was almost three times higher in men than women, while close contacts and neighbours of infected people had a sevenfold higher risk, reported D T Mourya, director, at Pune’s National Institute of Virology in the journal BMC Infectious Diseases earlier this year.

Since veterinarians, healthcare workers and control group tested negative, the study concluded infection risk in India was low as compared to other endemic countries.

Despite the low risk, disease surveillance must continue because many new infections and re-emerging diseases with low incidence in the past are now causing human outbreaks because of a combination of factors such as high population density, poverty and malnutrition, increased travel, unplanned urbanization, deforestation, and change in agricultural practices, such as mixed farming.

About 60% of infectious diseases and 70% of emerging infections in humans are zoonotic in origin, with two-thirds originating in wildlife. Apart from getting infected from animals, outbreaks are also fuelled by genetic changes in the air-borne virus that make them more deadly or easily transferrable between humans, as evident from the H1N1pdm09 epidemic, avian influenza (H5N1), and the Middle East respiratory syndrome coronaviruses (MERS-CoV) outbreaks. Since new viruses have never caused disease in humans before, we have no immunity against them, which makes the epidemic potential massive.

Over the past two decades, arthropod-borne viruses have also begun causing bigger and more frequent outbreaks of dengue, chikungunya, Japanese encephalitis, Congo fever, Kyasanur forest disease, and Zika, as have bat-borne viruses such as Nipah.

India’s network of Virus Research and Diagnostic Laboratory (VRDL) across states for early detection of viruses causing outbreaks or significant disease has helped quickly identify contain Zika in Rajasthan and Nipah in Kerala. These labs have also provided crucial surveillance data of re-emerging diseases, like chikungunya and Zika.

Chikungunya has been back since 2006 after remaining dormant for decades after the 1963 and 1973 outbreaks. Similarly, while Zika has been circulating in India since the 1960s, its caused concern only after microcephaly was detected during the Brazil outbreak in 2015-16, after which outbreaks were identified and contained in Gujarat, Tamil Nadu, Rajasthan and Madhya Pradesh.