The lingering shadow of Covid-19: Science, surveillance, and strategy

India's active Covid-19 cases climbed to 5,364 as of Friday, with 764 new infections and four more deaths. Kerala remains the worst-affected State, registering 192 new cases, followed by Maharashtra with 107. Assam is also reported to have 8 cases as on Saturday, and this year 5 cases have been cured and discharged.

The majority of infections show mild upper respiratory symptoms, including sore throat, fever, and body ache. Severe cases requiring hospitalization are relatively rare and predominantly affect individuals with pre-existing health conditions or compromised immunity. Hospitals in cities like Pune have reported an increase in Covid-19 patients, many of whom are unvaccinated or have not received booster doses. This highlight concerns about waning immunity and the potential for breakthrough infections.

Amid this uptick, a team at IIT Guwahati has introduced a promising new method for detecting and quantifying SARS-CoV-2, the virus responsible for Covid-19. The pandemic exposed major limitations in existing detection technologies. While PCR tests are accurate, they are slow and require sophisticated lab infrastructure. Antigen tests are faster but less reliable, and antibody tests are only useful post-infection.

Moreover, these methods are often impractical in low-resource settings or during large outbreaks. The newly developed technique aims to provide a simple, cost-effective alternative to current diagnostic tools.

It's important to note that Covid-19 had never truly disappeared. Global cases stood at around 46,000 in March 2025, dropped to 23,000 in April, and are now rising again since May.

The latest surge is being driven by a new Omicron subvariant, NB.1.8.1, a descendant of the XDV.1 lineage, itself a recombination of JN.1 and XDE variants. This strain has a slightly higher ability to bind to human cells, increasing its transmissibility. However, it doesn't appear to significantly escape immunity from previous infections, including those from JN.1 and other recent variants.

Since 2019, the virus has undergone over 140 mutations. However, the overall genetic makeup has changed very little-less than 1 per cent. These minor mutations have led to shifts in traits such as transmission, symptoms and se-verity, which occasionally trigger spikes in case numbers. Still, the likelihood of severe illness remains low due to widespread immunity built up over five years through repeated infections, both clinical and subclinical.

While the current vaccines remain effective against severe disease, health experts recommend booster doses for vulnerable populations, including the elderly and those with comorbidities. Even though the current Covid-19 surge is concerning, it is not expected to lead to a major health crisis due to the milder nature of the prevalent variant and the population's existing immunity.

However, sustained vigilance, timely vaccination, and adherence to preventive measures remain essential to mitigate the spread and impact of the virus. Covid-19 will continue circulating at low levels with occasional spikes, and people ought to remain vigilant.