Why you're more likely to catch TB in bars than in church — Kemri

Nairobi’s crowded bars, where conversations mix with booming music, coughs and laughter, are the ideal environment for tuberculosis to thrive and spread.

A new city-wide study that examines where TB patients may have contracted the disease, suggests that frequenting bars significantly increases the risk of contracting the disease compared to other social settings, such as churches or matatus.

While the findings have not yet been peer-reviewed, they offer valuable insights for public health efforts aimed at controlling TB transmission in urban environments.

The findings are based on a survey conducted in Nairobi in 2022 by researchers from the Kenya Medical Research Institute, Amref, and the University of Washington.

A total of 6,369 participants, aged 15 and above, were involved.  Those with TB symptoms had sputum samples taken and tested using advanced diagnostic techniques, including Xpert Ultra and culture tests.

They then answered questions on where they mostly spend time in the community, and how they commute. 

The activity locations were categorized as home, work, school, market, social (bars, gaming, sports club, or social halls), or church.

Overall, home was the most frequently reported location, followed by church, work, and market.

However, the final analysis indicates more people with TB frequented bars and other drinking dens compared to other social places.

"Only bars and other drinking venues were associated with a higher risk of TB," the authors reported. "No statistically significant association was found for other reported social activity locations."

Frequenting bars was associated with a four to five times higher risk of contracting TB than in other social environments.

 “This underscores the importance of spatially targeting active case finding efforts at these locations, particularly in urban settings like Nairobi,” the researchers said.

The study, titled Mobility Patterns, Activity Locations and Tuberculosis in Nairobi, is available on the preprint platform medRxiv.

The authors found that men and older adults, especially those aged between 45 and 54, are disproportionately affected by TB in Nairobi.

They had 2.4 times higher odds of contracting the disease than younger participants.

These findings are consistent with global TB data, which often show that men and older individuals are more susceptible to the disease.

However, the authors went a step further by linking these demographic groups specifically to frequenting bars, which emerged as the most significant risk factor in social settings.

“Men are less likely to report TB symptoms despite being at a higher risk,” the study revealed, pointing to a potential public health gap that needs addressing.

Kenya on average reports over 90,000 tuberculosis cases annually, according to the Ministry of Health’s national TB programme.

While bars were the only social setting found to have a statistically significant association with TB transmission, the study examined other communal locations.

None of these showed a comparable level of risk.

"Other reported social activity locations, including community venues, gaming halls and playgrounds, were not significantly associated with TB transmission," the study noted.

The authors believe that the conditions in bars—crowded spaces, poor ventilation and close interactions over extended periods—create a perfect storm for TB transmission.

“The data highlight bars as environments where prolonged, close contact between individuals can facilitate the airborne spread of TB bacteria, particularly in overcrowded or poorly ventilated spaces,” one author stated.

TB is primarily spread through airborne particles when an infected person coughs, sneezes, or speaks.

The bacteria can linger in the air for hours, making crowded places with limited airflow particularly high-risk environments.

The findings of this study hold significant implications for TB control strategies in Nairobi and other urban areas with similar social dynamics.

“Investigating the extent of this association and identifying particular social venues can help to inform national and local TB programmes on where to screen for TB,” the researchers suggested.

This would involve screening patrons and staff for symptoms, increasing public awareness about the risks associated with frequenting bars and potentially even modifying the layout and ventilation systems of such venues.

While matatus, another crowded setting, did not show the same level of risk, the researchers believe this may be due to the transient nature of interactions on public transport, where passengers are unlikely to spend as much time in close proximity as they would in a bar.

“Bus rides are typically short in duration and passengers are constantly moving in and out, reducing the likelihood of prolonged exposure,” the study explained.