New study casts doubt on the way in which TB is transmitted

Tuesday,19th October 2021 – The virtual 52nd Union World Conference on Lung Health (WCOLH) opened today by announcing three major scientific developments that will potentially impact the global response to tuberculosis (TB), the world´s second biggest infectious disease killer behind COVID-19.

The event takes place against the backdrop of ongoing COVID-19 vaccine inequity, with the pandemic continuing to impact the delivery of TB services in many low- and middle-income countries.

COVID-19 and TB are today the world´s two leading infectious disease killers. The novel coronavirus pandemic has refocused attention on how infectious diseases transmit from person to person and has catalysed innovations in sampling and diagnostics. The disruption to TB services during the pandemic has only highlighted just how important it will be going forward that testing for and treating TB are made simpler and easier to access.

Researchers question assumptions of how TB is transmitted

In the opening press conference today, researchers from the University of Cape Town in South Africa announced results from their study of TB positive people carried out in the specially constructed Respiratory Aerosol Sampling Chamber (RASC) which suggest that coughing, thought previously to be the main means of spreading TB, might not be the primary driver of TB transmission. Instead, tidal, or regular, breathing may be a far more significant contributor to the aerosolization of Mycobacterium tuberculosis, the bacterial cause of TB.

“This study is an important step forward in our understanding of aerosol transmission of disease and its findings are as relevant for COVID-19 as they are for TB,” said Guy Marks, President of The Union, convenor of the World Conference. “It will hopefully generate more focus on the topic of airborne spread of respiratory diseases.”

Lead author of the study, Ryan Dinkele of the University of Cape Town, said if tidal breathing is a primary driver, or even as important as cough in TB transmission, then symptomatic screening for TB-transmitters may not be useful in slowing the spread of the disease.

“The current approach, which relies on the testing and treatment of passively identified individuals may not be a reliable response to preventing transmission, as it depends on people feeling sick enough to seek treatment,” said Dinkele. “It may also shed light onto why constructing transmission chains is so challenging in high TB burden settings.”

Fingerstick blood test can detect TB in less than an hour

The development of a fast and accurate, non-sputum-based point-of-care triage test for tuberculosis (TB) would have a major impact on combating the TB burden worldwide. A new fingerstick blood test has been developed by Cepheid (Xpert-MTB-Host Response (HR)-Prototype).

Jayne Sutherland of the MRC Unit The Gambia at LSHTM, reported interim results of the Xpert-MTB-HR prototype trialled in a prospective, multi-site study across Gambia, Uganda, South Africa and Vietnam. The device is the first to meet the WHO target product profile for a Triage test for TB regardless of HIV status or geographical location. It takes under 1 hour and uses fingerstick blood, rather than sputum, which reduces biohazard risk and increases likelihood of diagnosis in individuals who cannot readily produce sputum such as children and people living with HIV.

Face-mask sampling can predict acquired Mycobacterium tuberculosis infection in household contacts

Caroline Williams, Clinical Lecturer in Infectious Diseases at the University of Leicester in the UK, reported on the use of masks to see if bacteria could be detected on the mask and therefore could potentially be used to detect infectiousness earlier than with sputum. Mask sampling could detect viable bacteria and those patients with higher levels on their mask correlated with increased infectiousness determined by new infections in their close contacts.

For further details, read the full press statement.

SEE ALSO:

• Health Policy Watch: Simple breathing can transmit TB more effectively than cough – new research debunks old convictions about transmission