Disease Outbreak News ,Zika virus disease – India

Between 1 January and 31 December 2024, a cumulative total of 151 ZVD cases were reported from three states in India (Gujarat, Karnataka, and Maharashtra states). Maharashtra State reported a cumulative total of 140 ZVD cases through the Integrated Disease Surveillance Programme (IDSP). Among the 140 cases, the majority (125 cases) were reported from Pune district, 11 from Ahmednagar district, and one case from each of Kolhapur, Sangli and Solapur districts and Mumbai suburban area. Additionally, Karnataka state reported ten cases in 2024, with seven reported from Bengaluru urban district and three from Shivamogga district. Gujarat state reported one Zika case in Gandhinagar Corporation in 2024.

The number of ZVD cases reported in 2024 in Maharashtra state is the highest since 2021 compared with respectively one, three and 18 ZIKV disease cases reported in 2021, 2022 and 2023. The number of cases reported in Karnataka state in 2024 is also the highest number reported since the first case reported in 2022.

The State IDSP Unit does not routinely disaggregate the number of ZVD cases (e.g. pregnancy status), therefore the number of ZIKV infection among pregnant women is unknown.

As of 31 December 2024, no cases of microcephaly and/or Guillain-Barre syndrome (GBS) associated with this outbreak have been reported.

Zika virus is a mosquito-borne virus first identified in Uganda in 1947 in a Rhesus macaque monkey and  evidence of infection and disease in humans was reported in other African countries in the 1950s. Zika virus is transmitted to humans by the bite of an infected Aedes mosquito. Zika virus is also transmitted from mother to fetus during pregnancy, as well as through sexual contact, transfusion of blood and blood products, and possibly through organ transplantation.

Zika virus (ZIKV) can cause large epidemics, particularly when introduced in immunologically naive populations, resulting in a substantial demand on the public health system including surveillance, case management, and differential laboratory diagnostic testing especially in case of co-circulation of other mosquito-borne diseases like dengue and chikungunya.  In most cases, infection with ZIKV is asymptomatic or mildly symptomatic and of short duration. However, infection during pregnancy is associated with a risk of microcephaly and other congenital malformation in infants (congenital Zika syndrome (CZS)) as well as preterm birth and miscarriage. Some ZIKV-infected adults and children may develop neurological complications including GBS, neuropathy and myelitis.

There is no specific treatment available for Zika virus infection or disease.

On 3 July 2024, the Government of India issued an advisory for all States following the detection of ZIKV disease cases in Maharashtra state and the following public health measures:

• The IDSP at the National Centre for Disease Control is mandated with surveillance and response to 40 plus outbreak-prone communicable diseases, including the ZIKV. Every State has designated laboratories, such as District Public Health Laboratories and State Referral Laboratories, under the IDSP for investigation and surveillance of these diseases.
• Technical Guidelines for Integrated Vector Management, and effective community participation disseminated to the States for implementation.
• Under the National Health Mission, budgetary support is provided to States/Union Territories for preventive activities such as provision of domestic breeding checkers (workers who inspect homes for mosquito breeding sites and eliminate them), involvement of accredited Social Health activists, insecticide, fogging machines, training support, awareness activities.

In Maharashtra, the State authority conducted active surveillance following the detection of the initial ZIKV disease cases, particularly targeting pregnant women. Close monitoring of ZIKV- positive pregnant women has been conducted. Vector control measures have been intensified in affected areas.

Zika virus can cause large epidemics, particularly when introduced in immunologically naive populations, with a substantial demand on the public health system, including surveillance, case management, and differential laboratory diagnostic testing to differentiate ZVD from illness due to co-circulating mosquito-borne viruses like dengue and chikungunya. ZIKV is primarily transmitted by Aedes species mosquitoes, it can also be transmitted from mother to fetus during pregnancy, through sexual contact, transfusion of blood and blood products, and organ transplantation. Although 60-80% of Zika virus infections are asymptomatic or only have mild symptoms, ZIKV infection can cause GBS and microcephaly and congenital Zika syndrome (CZS) during pregnancy.

India reported its first Zika case from Gujarat State in 2016. Since then, many other States namely Tamil Nadu, Madhya Pradesh, Rajasthan, Kerala, Maharashtra, Uttar Pradesh, Delhi, and Karnataka have reported cases subsequently, but no ZIKV-associated microcephaly has been reported. Although Zika virus is not unexpected in Maharashtra state, given the wide distribution of the vectors, Aedes aegypti, and Aedes albopictus, across India, the number of ZVD cases reported in Maharashtra state in 2024 is much higher than the numbers reported in previous years and is thus unusual. The actual incidence of ZVD could be higher due to the asymptomatic or mild clinical presentation in most of the ZIKV infections, combined with varied level of awareness among clinicians. Aedes mosquito density in India varies by season and location, with the highest densities occurring during the monsoon and post-monsoon seasons.

Protection against mosquito bites during the day and early evening is a key measure to prevent ZIKV infection. Special attention should be given to preventing mosquito bites among pregnant women, women of reproductive age, and young children.

Aedes mosquitoes breed in small water collections inside and around homes, schools, and workplaces. It is important to eliminate these mosquito breeding sites by appropriate methods, including covering water storage containers, removing standing water in water-holding containers such as vases and flowerpots, and cleaning up trash, unused containers, and used tyres. Community initiatives are essential to support local health authorities and national public health programmes to reduce mosquito breeding sites. Health authorities may also advise the use of larvicides and insecticides to reduce mosquito populations and disease spread. Semi-urban areas should prevent the breeding of Aedes spp., in rubber plantations and other stagnant pools of water.

Basic precautions for protection from mosquito bites should be taken by people travelling to high-risk areas, especially pregnant women. These include wearing light-colored, long-sleeved shirts and pants, ensuring rooms are fitted with screens to prevent mosquitoes from entering, and using of insect repellents that contains N,N-Diethyl-meta-toluamide (DEET), IR3535 or Icaridin according to the product label instructions.

For regions with active transmission of ZIKV, all persons with suspected ZIKV infection and their sexual partners (particularly pregnant women) should receive information about the risks of sexual transmission of ZIKV.

WHO recommends that sexually active men and women be correctly counselled about ZIKV infection and offered a full range of contraceptive methods to be able to make an informed choice about whether and when to become pregnant to prevent CZS and other possible adverse pregnancy and foetal outcomes. Men and women should be informed about the possible risk of sexual transmission of Zika virus during the three months and two months, respectively, after known or presumptive infection, and should be informed about the correct and consistent use of condoms or abstinence during that time period to prevent Zika virus infection through sexual transmission.

Women who have had unprotected sex and do not wish to become pregnant due to concerns about ZIKV infection should have ready access to emergency contraceptive services and counselling. Pregnant women should practice safer sex (including correct and consistent use of condoms) or abstain from sexual activity for the entire duration of pregnancy. Pregnant women should be encouraged to attend scheduled appointments and enhanced antenatal care and follow-up, including ultrasound imaging to detect microcephaly and other developmental anomalies associated with ZIKV infection in pregnancy, in accordance with the state/national response plan.

For regions with no active transmission of ZIKV, WHO recommends practicing safer sex, including postponing sexual debut, nonpenetrative sex, correct and consistent use of male or female condoms, and reducing the number of sexual partners, or abstinence for a period of three months for men and two months for women who are returning from areas of active ZIKV transmission to prevent infection of their sex partners. Sexual partners of pregnant women, living in or returning from areas where local transmission of ZIKV occurs, should practice safer sex or abstain from sexual activity throughout pregnancy.

WHO does not recommend any travel or trade restriction to India based on the current information available.

• India Union Health Ministry. 3 July 2024. Union Health Ministry Issues Advisory to States in view of Zika virus cases from Maharashtra(link is external)
• India Ministry of Health and Family Welfare. 30 July 2024. Update On Efforts Taken to Control Zika Virus in The Country(link is external)
• WHO 2018: Zika virus disease
• WHO guidelines for the prevention of sexual transmission of Zika virus
• WHO Zika virus factsheet
• Vector control operations framework for Zika virus (who.int)
• PAHO/WHO Tool for the diagnosis and care of patients with suspected arboviral diseases (link is external)
• Disease Outbreak News: India – Zika 2017
• Disease Outbreak News: India – Zika 2021

Citable reference: World Health Organization (29 January 2025). Disease Outbreak News; Zika virus disease in India. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON549