The global lockdown caused by Covid-19 risks a "devastating" surge in tuberculosis cases, with nearly 1.4 million additional deaths from the world's biggest infectious killer by 2025, new research showed on Wednesday.
TB, a bacterial infection that normally attacks patients' lungs, is largely treatable yet still infects an estimated 10 million people every year.
In 2018, it killed around 1.5 million people, according to the World Health Organization (WHO), including more than 200 000 children.
Since effective medication exists, the world's TB response is centred on testing and treating as many patients as possible.
But as Covid-19 forces governments to place populations on lockdown, new disease models showed that social distancing could lead to a disastrous rebound in TB infections - the effects of which are set to persist for years.
This is because social distancing will make it impossible for health care workers to test vulnerable populations and for patients to access ongoing treatments.
"In spite of having drugs and treatment... we are not yet close to ending it and TB remains the biggest infectious disease killer," said Lucica Ditiu, executive director of the Stop TB Partnership.
"Covid has hit us very hard. The more people we have not diagnosed and treated the more problems we will have in the coming years."
Length of lockdown crucial
Models developed in partnership with epidemiologists at Imperial College London used TB response data from three high-incidence countries: India, Kenya and Ukraine.
They showed that a two-month global lockdown and a rapid recovery in response programmes could lead to more than 1.8 additional TB infections globally over the next five years, and a predicted 340 000 deaths.
But if countries fail to quickly reimplement their testing and treatment, the models showed things would get much worse.
For example, a three-month lockdown followed by a 10-month "recovery" period could lead to an additional six million infections and 1.4 million TB deaths by 2025.
"TB is actually curable with affordable drugs. So a lot of control efforts in recent decades have really been focused in diagnosing cases as quickly as possible," said Nimalan Arinaminpathy, associate professor in mathematical epidemiology at Imperial.
"Lockdowns and other measures against coronavirus are affecting these systems for managing tuberculosis. In fact (in the models) it takes several years for this elevated TB burden to come down to pre-lockdown levels."
The research did not look at the comorbidity between TB, an acute lung infection that leaves even survivors' lungs compromised, and Covid-19, a viral infection that often leads to lung problems.
Cheri Vincent, head of TB division at USAID, said several studies were looking into how TB puts an individual at higher risk of getting sick with Covid-19.
"As that information becomes available we may be looking at a much more dire situation," she said.
Suvunand Sahu, deputy executive director of Stop TB Partnership, said there was significant concern over the millions of people living with the infection as Covid-19 spreads.
"We know that TB does create damage in the lungs, so when your lung capacity is limited adverse outcomes of Covid would naturally be expected to be higher," he said.