What makes long Covid long

New evidence on blood abnormalities in long Covid raises fresh concerns for millions in India, but also inspires diagnostic hope

- SOHINI DAS

More than five years after the first wave, Covid-19 continues to cast its shadow over India’s health landscape. A new study published in the Journal of Medical Virology (October 2025) has added renewed urgency to the need to tackle a subject clinicians have been flagging over the years: Persistent blood abnormalities in long Covid patients that may be causing chronic fatigue, cognitive problems, and cardiovascular symptoms.

‘The study — led by researchers from France and South Africa — found that long Covid patients showed lasting changes in their ‘complement system’ — a group of 20 proteins that are integral to natural immunity.

‘The markers of ‘complement activation’ remained elevated long after the infection itself had abated, reinforcing the theory that chronic immune activation and tiny, hard-to-detect blood clots are central to long Covid’s persistence.

Although the findings don’t prove that these clots cause long Covid, they strengthen the theory that persistent immune and vascular dysfunction play an important role.

For India, the implications are significant — around 45 million Covid infections have been officially reported since 2020. But actual numbers may be far higher because of unreported incidence of a single person contracting Covid multiple times.

A study led by Banaras Hindu University (BHU) researchers published in the International Journal of Infectious Diseases in 2023 estimated that the actual coronavirus cases in the country may have been between 580 to 980 million. The research has shown that “the actual corona infection in India was at least 17 times higher," according to a statement by BHU last year. This could be due to the overwhelming number of asymptomatic people, which was several-fold higher than those who showed symptoms — the basis for the official count.