# Reducing tuberculosis transmission by genotype-based contact tracing coupled with public health containment measures: a case study during the COVID-19 pandemic in Taiwan

## TL;DR

This study shows that combining genetic tracing with public health measures during the pandemic reduced tuberculosis spread in Taiwan.

## Contribution

A novel genotype-based contact tracing method was used to estimate TB transmission reduction during the pandemic.

## Key findings

- An 81% reduction in TB transmission was observed during the first two years of the pandemic.
- Genotype-based contact tracing combined with public health measures significantly reduced TB cluster cases.
- The approach could help moderate-burden TB countries reach WHO End TB targets by 2035.

## Abstract

This study aimed to estimate the effectiveness of genotype-based contact tracing coupled with public health and social containment measures (PHSMs) in reducing tuberculosis (TB) transmission during the COVID-19 pandemic. Patients suspicious of recent TB infection from index cases were traced by genotyping method between 2017 and 2021. To make allowance for TB cases attributed to reactivation, TB cases identified from the genotype-based contact tracing group were compared to those from the underlying population via the notifiable nationwide system without genotyping. The relative changes (ratios) in TB cases before and during the pandemic between the two groups were leveraged to estimate the effectiveness of PHSMs following genotype-based contact tracing, taking into account demographic features and geographic variation, with a multivariable Poisson regression model. Before the pandemic, we identified 42 of 133 (31.6%) sputum culture-positive index (SCI) patients via 344 genotype-matched clustered TB cases. During the pandemic, 11 of 70 (15.7%) SCI patients were linked to 36 clustered cases. The annual average of TB-clustered patients for the genotype-based contact tracing group decreased by 84.3%, whereas the corresponding figure for the comparator decreased by 18.5%. The adjusted relative risk of 0.19 (95% CI 0.14–0.28) gave an 81% TB transmission reduction after controlling for extraneous factors. Genotype-based contact tracing coupled with PHSMs significantly reduced TB transmission. Our findings from the pandemic period demonstrate that a molecular epidemiological approach with public health containment measures will enable a moderate-burden TB country to reach the WHO End TB targets by 2035.

The extent to which COVID-19 public health and social measures reduced tuberculosis transmission remains unclear. We elucidated the recent tuberculosis infection with a novel genotype-based contact tracing from 2017 to 2021. These patients were recruited as the contact tracing group in contrast to the comparison group of tuberculosis cases from the general population via the notifiable nationwide system without genotyping. The relative changes in tuberculosis cases before and during the pandemic between the contact tracing group and the comparison group were used to estimate the effectiveness of reducing tuberculosis transmission. We found a significant 81% reduction in tuberculosis transmission during the first 2 years of the pandemic. This finding demonstrates that a molecular epidemiological approach with public health containment measures will enable a moderate-burden tuberculosis country to reach the End TB targets by 2035.