India lacks diagnostic tests for emerging infectious diseases

The recent Zika virus case in Pune has rekindled concerns about India's preparedness to diagnose emerging infectious diseases. The 46-year-old doctor, who experienced symptoms such as fever and rash, was admitted to hospital and diagnosed with Zika virus infection after his samples were sent to the premier virology laboratory for testing. Subsequent testing of his family members revealed that their 15-year-old daughter was also infected. This is not the first time that Zika virus has been confirmed in India. Cases have been confirmed in several Indian states in the past, most recently in 2021 with major outbreaks in Kerala and Uttar Pradesh.

Zika virus is a mosquito-borne pathogen that belongs to the Flaviviridae family, which also includes dengue fever. Clinical symptoms of Zika virus infection are often mild and indistinguishable from other infectious diseases, including dengue fever. However, Zika virus poses a significant risk to pregnant women, as it can be transmitted from mother to child and can cause microcephaly in the offspring.

With climate change, it is not surprising that multiple dengue outbreaks are making headlines. The same vectors that spread dengue can also spread Zika. However, due to poor surveillance of Zika in India, we may never fully understand its spread. In March 2023, CDSCO, India's apex diagnostic approval body, confirmed that there is no approved diagnostic test for Zika. This limitation complicates diagnosis as Zika cannot be diagnosed solely on classic symptoms and high clinical suspicion, resulting in a simultaneous surge in dengue cases across the country. ICMR surveillance of Aedes aegypti mosquitoes has shown positive Zika virus following human cases, indicating that many cases are likely being missed.

Zika is not an isolated case. Recent reports of avian influenza A/H5N1 infection in a child who travelled to India from Australia suggest further undetected infections. Despite multiple outbreaks of avian influenza affecting poultry in India this year, including an ongoing outbreak in Kerala, human testing and surveillance remains limited. This is exacerbated by a lack of widely available diagnostic tests and an over-reliance on a few apex institutions.

Consider the case of Nipah virus, which has had multiple outbreaks in Kerala. India has seen several Nipah virus outbreaks, particularly in West Bengal (2001 and 2007) and Kerala (2018, 2021, 2023). In Kerala, identification of the virus relied heavily on clinical suspicion. Some cases were missed at the time of initial admission due to lack of routine testing, which was mainly due to non-ready availability of diagnostic facilities except at the highest level national laboratories, leading to complexities in testing, delays, and consequent loss of valuable time to take measures. Rapid identification and isolation of cases, contact tracing, and targeted screening of contacts are key to effectively contain Nipah virus outbreaks.

Rapid development of widely available and accessible diagnostics, especially during outbreaks, requires in the first place that whole genome sequences from the outbreak be rapidly available in the public domain apart from an independent and time-bound qualification process. While many countries have granted emergency approval to diagnostics based on synthetic genomic material, India has required validation in clinical samples that are not easily accessible. These limitations impede rapid development. Although there have been multiple publications on Zika and Nipah outbreaks over the years, genomes from these outbreaks are still not being rapidly released in public repositories. For example, the genome of the Nipah virus that emerged in Kerala in 2023 was released only last month. Despite ongoing avian influenza outbreaks in multiple states, whole genome sequences are still not available in GISAID, the main repository for influenza sequences, hindering our understanding of the disease and its spread and, more importantly, our ability to rapidly develop and deploy diagnostics.

During the COVID-19 pandemic, India rapidly expanded its testing infrastructure by rapidly decentralizing and leveraging its existing network of hospitals, medical colleges, and private laboratories across the country and engaging industry with a systematic approach to diagnostic test approval to make diagnostics widely available. Experience gained from the COVID-19 pandemic can serve as a stepping stone to improve testing capacity for other emerging diseases.

India can ensure a more effective response to future epidemics, especially by decentralizing testing facilities at the district and subdivision levels and developing accessible and affordable diagnostic tests for Zika, Nipah virus, avian influenza and many other emerging diseases. There has never been a better time to rapidly build decentralized systems for diagnostics, genomic surveillance and data sharing to enable emerging infectious disease preparedness and public health response.

(Vani Jolly is a senior scientist at Karkinos Healthcare and Vinod Scaria is a senior consultant at Vishwanath Cancer Care Foundation and an adjunct professor at Indian Institute of Technology Kanpur and DY Patil Vidyapeeth.)