Is COVID-19 leading to a flare-up of tuberculosis in the State?
While there is no conclusive evidence yet to establish that COVID-19 can directly trigger an increase in tuberculosis, TB cases have indeed been going up in the State, especially in the post-COVID phase.
Some clinicians feel that much of the new TB cases could be cases of delayed diagnosis during the pandemic. However, emerging evidence from various studies suggest that COVID and TB share a dysregulation of immune responses and the possibility of COVID-19 activating dormant/latent TB infection or triggering re-infections in those recovering from COVID is indeed real.
Pulmonologists in Kerala are now reporting new TB infections amongst persons within four-six weeks of recovering from COVID-19 . With 10 such cases already reported, the Health Department has now issued an advisory that routine TB screening be made mandatory in all post-COVID clinics.
As both TB and COVID-19 are diseases which primarily attack the lungs, most of the symptoms that manifest — cough, fever, breathing difficulty — are similar for both. Thus, lingering or persistent respiratory symptoms in people who have recovered from COVID could well be mistaken as residual issues of COVID or secondary bacterial infections, missing TB diagnosis totally.
“Routine TB detection had taken a back seat during the pandemic. TB is a disease which progresses slowly and people may relate their symptoms such as cough and fever to be part of the seasonal illness and ignore it. When these people are hospitalised with COVID, the patches that show up in lung X-rays are assumed to be those due to COVID. Thus many of the TB cases which are now surfacing are cases which we failed to pick up earlier from the community,” says Ajith Bhasker, a pulmonologist in Kozhikode.
Not everyone exposed to the bacteria, Mycobacterium tuberculosis , gets infected immediately. While the infection manifests as active TB disease in some, in a few others, the bacteria can live long in the body without ever causing active disease, a condition known as latent TB. Latent TB can get activated into active TB when the body’s immune system is weak.
In Kerala, the prevalence of latent TB is estimated to be 20%. The 10 cases of TB, detected within four to six weeks after treatment for COVID-19, are just the tip of the iceberg and early pointers that there could be many more cases in the community that need investigation. Most of these patients had diabetes and had been treated with steroids as part of COVID treatment.
“Further studies are needed to ascertain if COVID actually precipitated TB in these patients. Some of the patients with COVID are treated with corticosteroids even when there is no proper indication, that too at inappropriately high doses. Such irrational use of steroids can lead to immunosuppression, which heightens the risk of reactivation of dormant infections such as latent TB or opportunistic secondary infections like mucormycosis,” says P.S. Rakesh, WHO consultant, National TB Elimination Programme.
It is argued that since infection control against airborne diseases have been strengthened during COVID in hospitals and elsewhere, the possibility of an increase in TB infection cannot be real. But airborne infection control can prevent only immediate infection, whereas in Kerala, most of the new TB cases are a re-activation of some exposure that these persons had much earlier.
The new government advisory says it is important that patients with persistent respiratory symptoms immediately after recovering from COVID are evaluated for TB. It is through systematic screening in post-COVID clinics, that the 10 new TB cases were detected in the State.
TB screening should be a routine practice in all post-COVID clinics and health workers have also been asked to check for TB symptoms in patients they meet in the field and who are recovering from COVID.
