As India again reports Zika virus case, focus turns to vaccine, testing

Bharat Biotech's Zikavac now in clinical trial; labs look to offer Zika virus test

Zika virus cases are again being reported from parts of the country, with Karnataka now recording its first case – a five-year-old girl from Raichur district. Earlier this month, a 67-year-old man from Nashik, Maharashtra, had tested positive after he was admitted to a Pune hospital. India had also reported a spike in cases in June-July.

Confirming that this is the first Zika case in the state, Karnataka Health Minister K Sudhakar has said the government is monitoring the situation closely.

Meanwhile, a Zika vaccine is awaited, with Bharat Biotech’s Zikavac now in clinical trials.

The development of a vaccine would be critical for fighting this mosquito-borne flavivirus with India reporting cases periodically.

What is Zika virus?

Zika virus, a mosquito-borne flavivirus, was first isolated in 1947 from the blood of a rhesus monkey in Zika forest of Uganda. There have been outbreaks ever since, mostly in Africa, South America and so on.

It peaked in early 2016 with the cumulative number of documented and suspected cases exceeding 1 million. But 2017 onwards, cases of Zika have been waning.

India has never been one of the key geographies where the virus has broken out into epidemics. However, a study by scientists of the Indian Council of Medical Research (ICMR), published in the Frontiers in Microbiology in June, showed that the virus has been ‘silently’ spreading across the country.

Surveillance in 2021 showed the virus’ presence in states like Kerala, Uttar Pradesh and Maharashtra. Enhanced surveillance confirmed its presence in Jharkhand, Rajasthan, Punjab, Telangana and Delhi the same year. ICMR experts noted that the detection of cases in new states indicates local virus transmission.

Does India have enough testing capacity for Zika?

Doctors point out that lack of diagnostic testing options for the Zika infection may leave many cases undetected, which may pass off as suspected dengue or viral fever as the symptoms are largely similar.

The problem with the detection of Zika virus cases is the lack of widespread diagnostic tools, doctors say.

K Seshi Kiran, consultant physician, Yashoda Hospitals, Hyderabad, had told Business Standard in July: “There is hardly any private laboratory testing for Zika virus. Therefore, even if we suspect a case, it is very difficult to verify it. Most often, Zika cases pass off as suspected dengue cases as the symptoms are similar.” He added that they attend to several cases of viral fever, which, upon investigation, turn out to be dengue-negative.

What are Zika symptoms?

Symptoms of Zika are largely similar to viral fever. Anita Mathew, infectious disease specialist, Fortis Hospital, Mulund in Mumbai, says that most patients complain of fever, redness of the eyes or conjunctivitis, rashes, body ache and joint pain. Since there is no specific medication for Zika, patients are given symptomatic treatment, and the symptoms usually go away within a week or so.

The problem occurs when a pregnant woman is infected by the virus.

“Zika virus infection during pregnancy is a cause of microcephaly and other congenital abnormalities in the developing foetus and newborn. Zika infection in pregnancy also results in pregnancy complications such as foetal loss, stillbirth, and preterm birth,” the World Health Organisation (WHO) notes. 

Microcephaly is a birth defect where a baby's head is smaller than expected when compared to babies of the same sex and age. Babies with microcephaly often have smaller brains that might not have developed properly, the Centres for Disease Control and Prevention (CDC), the national public health agency of the United States, says.

Kiran and Mathew both say that while the virus is mostly transmitted through mosquito bites (daytime bites similar to dengue), there are instances when the virus has been transmitted through sexual intercourse.

“Zika virus can be detected through RT-PCR, blood, urine and semen tests. If the virus is found in the semen, abstinence for at least eight weeks is advised,” Kiran says.

Vaccine and testing

Leading private diagnostic laboratories tell Business Standard that they are now gearing up to add a Zika virus test to their test menu.

Pune-based Mylab Discovery Solutions, which developed the country’s first indigenous Sars-CoV-2 RT-PCR and the first rapid-antigen home test kit, has launched India’s first combined RT-PCR test kit for monsoon diseases in July. It can differentiate among malaria, chikungunya, dengue, Zika, leishmaniasis, leptospirosis and salmonellosis.

Bharat Biotech had said in 2016 that it had achieved a breakthrough in developing the world’s first promising candidate for Zika virus in Zikavac. “We believe we have an early-mover advantage in developing the Zikavac and we are probably the first in the world to file for a global patent for Zika vaccine candidates,” the company had then said.

It had two candidate vaccines under development then – one of them an inactivated vaccine that had reached preclinical testing in animals.

The company has now again started actively working on its Zika vaccine – BBV121. “BBV121 (zika vaccine) is under active product development, and phase 2 human clinical trials will follow,” Bharat Biotech told Business Standard.

In 2016, big pharma like Pfizer, Johnson & Johnson (J&J) and Merck were evaluating developing a Zika vaccine. According to reports, globally, several Zika vaccine candidates on a variety of platforms are under development – DNA-plasmid technology, mRNA, attenuated live virus, viral vector vaccines, etc.

Infectious disease specialists like Mathew and Kiran say the silver lining is that Zika virus infection is relatively benign compared to malaria, dengue and chikungunya, and mostly resolves on its own with hardly any mortality.