India has registered a rise in COVID-19 cases beginning from last week of May this year. As of June 16, the country has 7,264 active cases. The World Health Organisation in its recent report (week of May 19 to 25 2025) that SARS-CoV-2 activity was generally low globally, though elevations have been reported in a few countries in Central America and the Caribbean, Tropical South America, South West and Northern Europe, Western Asia, Southern Asia, South-East Asia, and Eastern Asia.

While doctors have stressed that there is no need to panic as a majority of the cases are mild and do not require hospitalisation, this spike in cases, has brought to the fore once again, several associated health risks including deep vein thrombosis (DVT) — both during and after infection.

“This risk of DVT remains elevated even after recovery from Covid-19, with the risk ratio increasing up to 70 days post-infection,’’ said Anil Bansal, member, Delhi Medical Association (DMA). The risk is particularly high in the first week after diagnosis. While the risk decreases in subsequent weeks, it remains elevated for several weeks post-infection, he added.

Understanding DVT

Deep vein thrombosis (DVT) occurs when a clot forms in one of the deep veins of the body. This usually occurs in the leg. DVT can be dangerous, as the blood clot can break free and travel through the bloodstream. If the blood clot gets lodged in the lung and blocks blood flow, it can lead to pulmonary embolism, which can be life threatening.

Venous thromboembolism (VTE) occurs with deep vein thrombosis (DVT) and pulmonary embolism (PE). It can result in significant mortality, morbidity, and healthcare costs. Approximately 30% of patients with symptomatic VTE manifest with PE, and others with DVT. The incidence of DVT in India in the general population is about 1.79 per thousand. More than 50% of post-surgical procedure patients are at risk of developing VTE. The prevailing notion that the incidence of VTE in Asians is less than that in the Western population has been disproved by recent reports.

Task force report

Previously, a taskforce report by the National Academy of Medical Sciences (India), Delhi on Venous Thromboembolism had noted that in view of the ageing population of India and the increasing burden of non-communicable diseases along with infectious diseases affecting healthcare service delivery, there is a dire need to understand the early impact on the incidence and burden of deep venous thrombosis (DVT) and pulmonary embolism (PE) in India.

Increasing age, being male, trauma, surgery, prolonged hospitalisation, malignancy, neurologic disease, central venous catheter, prior superficial vein thrombosis, and varicose veins have been identified as some of the major risk factors for developing VTE. In women, oral contraceptive pill use, pregnancy, and hormone replacement therapy are established as independent risk factors. Some of the important risk factors for surgical patients developing VTE are age, type of surgery, length of procedure, and duration of immobilisation.

The task force stated that appropriate prevention and management of VTE was vital but in India, lack of trained human resources (healthcare professionals); inadequate laboratory diagnostic support; inadequate availability of pharmaceutical supplies; lack of awareness in the community; need for suitable research along with equitable distribution of facilities for the management of VTE – hamper 100 per cent safety of patients.

The Covid-19-DVT link

Aabid Amin Bhatt, medical director, Ujala Cygnus Group of Hospitals explained that COVID-19 and its link with a higher chance of VTE, including DVT and PE, is now well established.

“This link comes from the virus’s ability to cause a strong inflammatory reaction, often called a cytokine storm, which can disrupt the usual way blood clots. Research has found that patients, particularly those in the hospital with severe COVID-19, have a hypercoagulable state, meaning their blood is more likely to clot. The virus also directly harms the endothelial cells that line blood vessels, which further increases the risk of clots forming,’’ said Dr. Bhat. He added that recent research indicates that even after recovery, individuals who had COVID-19 may remain at an elevated risk for thrombotic events for several months.

This has prompted ongoing updates to clinical guidelines recommending thromboprophylaxis (blood thinning treatment) during hospitalisation and, in some cases, even post-discharge. The medical community now regards COVID-19 not just as a respiratory illness, but also as a systemic vascular disease with serious implications for blood clotting and cardiovascular health, he said.

Severe Covid-19 and vaccines

Abhishek Bansal, senior consultant and chief interventional radiologist, Aakash Healthcare said that a very high percentage of patients admitted with severe COVID-19 infections were observed to be affected by this condition. “This was noted to be primarily because they had been hospitalised in the ICU for extended periods. Any duration of immobilisation or prolonged bed rest was noted to increase the risk of developing DVT or pulmonary embolism,’’ he said.

Dr. Bansal stressed that COVID-19 vaccines demonstrated that they are highly efficacious in preventing the occurrence of DVT and pulmonary embolism. “At the same time, some concerns had been raised about the vaccines themselves potentially causing DVT in a few individuals. However, it has been clearly documented that this risk is extremely low—estimated at approximately one in 10 lakh (one million) patients. Even in such rare cases, the condition is generally mild. It has been emphasised that if the individual had instead suffered from an actual COVID-19 infection, the risk of developing DVT or pulmonary embolism would have been substantially higher,’’ he said.

Treating and tracking

“Anticoagulant medicine have now been added as a standard treatment protocol of Covid-19 and many deaths have been prevented after we established the relationship between the two medical conditions, ’’ noted. Surinder Kumar Gupta, associate director, pulmonology, Paras Health, Panchkula.

Meanwhile, the WHO noted that it is currently tracking several SARS-CoV-2 variants including variants of interest (JN.1) and variants under monitoring (LP.8.1, NB.1.8.1, XEC, KP.3.1.1, KP.3, and LB.1).

“The most prevalent variant, LP.8.1, accounted for 27% of all submitted sequences in the week ending on 25 May 2025 which is a decrease from 32% in the week ending on 27 April 2025. NB.1.8.1 accounted for 21% of all submitted sequences in the week ending on 25 May 2025, a significant increase from 9% in the week ending on 27 April 2025,’’ it said in the recently released data.

WHO added that during this reporting period, all other variants showed a stable or decreasing trend.

“Available evidence suggests that JN.1, XEC, LP.8.1, and NB.1.8.1 do not pose additional public health risks relative to other currently circulating SARS-CoV-2 variants,’’ it said.

At the regional level, LP.8.1 decreased in the Americas and the Western Pacific Region, but slightly increased in the European Region. XEC decreased in all regions with sufficient data. NB.1.8.1 increased in the Americas, Europe, and the Western Pacific Region, but decreased in South-East Asia.