Expert Comment – Zika outbreak across India
3 February 2025 London School of Hygiene & Tropical Medicine London School of Hygiene & Tropical Medicine https://lshtm.ac.uk/themes/custom/lshtm/images/lshtm-logo-black.png
Health agencies are monitoring a higher than average number of Zika virus infections reported by some states across India.
Since the global 2015-2017 Zika pandemic, India has experienced sporadic Zika virus outbreaks. According to recent data released by the World Health Organization, three states across the country, Gujurat, Karnataka and Maharashtra, reported 151 cases of Zika virus disease between 1 January and 31 December 2024.
The number of cases documented for both Maharashtra and Karnataka states are the highest since their first reported cases in 2021 and 2022, respectively. Experts believe that the actual incidence of Zika virus cases in India could be higher, due to the asymptomatic or mild clinical presentation seen in most infections, combined with a varied level of awareness and reporting.
Zika is an arthropod-borne virus, known as an arbovirus, spread to people primarily through the bite of infected Aedes mosquitoes. It was first identified in Uganda in 1947, and a total of 89 countries and territories have reported evidence of mosquito-transmitted cases thus far.
Other arboviruses include dengue, Oropouche and chikungunya.
Most people have few or no symptoms if infected with Zika virus but some can develop life-threatening complications.
Zika infections can also be transmitted from mother to fetus during pregnancy. In October 2015, clinicians in Northeast Brazil noted a striking increase in the number of newborns with microcephaly, a condition in which children are born with abnormally small head circumferences. Analyses conducted by researchers at the London School of Hygiene & Tropical Medicine (LSHTM) and partners across Brazil confirmed a link between the microcephaly epidemic and infection with Zika.
Elizabeth Brickley, Professor of Epidemiology & Planetary Health at the Centre for Epidemic Preparedness and Response at LSHTM said: “The current outbreak of Zika across regions in India is not unexpected but it is concerning, particularly as the virus has the potential to cause large outbreaks in high-density urban settings.
“Zika virus is primarily transmitted to people through the bite of Aedes mosquitoes, which are endemic in India. Most people infected with Zika virus will have few or no symptoms and those who do will usually experience a rash, fever and painful joints, lasting around 2 to 7 days.
“However, evidence has shown that in rare cases, some people infected with Zika may develop Guillain-Barré Syndrome, a rare complication of infection in which a person’s immune system mistakenly attacks their own nerves, resulting in loss of sensation, weakness, and potentially life-threatening paralysis.
“Zika virus infections during pregnancy have also been shown to cross the placenta and disrupt fetal development, which can result in a range of abnormalities, including microcephaly and neurodevelopmental delays, that are collectively known as Congenital Zika Syndrome.
“The World Health Organization reports that the 2024 outbreak in Maharashtra has not yet been associated with any known cases of Guillain-Barré Syndrome or microcephaly; however, it is important to note that it is too soon to rule out complications associated with Zika virus infections during pregnancy in this outbreak.
“Since the largest epidemic of Zika last occurred in 2015 to 2016, the global transmission of the virus has decreased but the possibility of a re-emergence remains. It’s likely that rising temperatures associated with climate change may shift the geographic distribution of the Aedes aegypti mosquitoes that transmit Zika virus, which may increase the frequency of infections in regions where risks have historically been low and populations have little pre-existing immunity.
“As there are currently no vaccines to prevent infections with Zika virus or specific treatments for those who become unwell, protecting against mosquito bites during the day and early evening is a key measure to preventing Zika infections. Special attention should be given to preventing mosquito bites among pregnant women and those planning to conceive.
“As individuals, our best strategies for preventing mosquito bites include wearing long-sleeved clothing and using insect repellents. Other simple household interventions, such as cleaning up scrap material and covering water storage containers, may also reduce mosquito breeding sites and lower the risk of transmission.”
Research at the London School of Hygiene & Tropical Medicine (LSHTM)
Researchers at LSHTM are working with partners at the Universidade de Pernambuco, the Universidade Federal de Pernambuco, and the Fundação Oswaldo Cruz (Fiocruz) in Brazil on the Long-term Impacts for Families affected by the Epidemic of Zika (LIFE Zika) Study.
This project will follow school-aged children with and without exposure to Zika virus during pregnancy to answer critical questions about the children’s health and learning needs, and to improve understanding of the long-term impacts for affected children’s families.
Find out more here.
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