Travel Medicine and Infectious Disease 53 (2023) 102568
Contents lists available at ScienceDirect 
Travel Medicine and Infectious Disease 
journal homepage: www.elsevier.com/locate/tmaid 
World tuberculosis day 2023 – Reflections on the spread of drug-resistant tuberculosis by 
travellers and reducing risk in forcibly displaced populations  
A R T I C L E  I N F O   
Keywords 
Tuberculosis 
World TB Day 
Travellers 
Refugees 
MDR-TB 
Control 
Vaccines       
World Tuberculosis (TB) Day, March 24th, 2023, will commemorate All travellers who move by air, land or sea face the perennial po-
the day in 1882 when Professor Robert Koch announced his discovery of tential risk of airborne or droplet-borne transmission or acquisition of 
Mycobacterium tuberculosis (Mtb) when TB ravaged Europe. Over a cen- respiratory tract infections, including TB [6,7,8]. Over the past decade, 
tury later, in 1993, the World Health Organization (WHO) declared TB a multidrug-resistant TB (MDR-TB) has become an increasingly important 
global health emergency. Since then, there have been 60 million deaths public health problem in Asia, Africa, and Eastern Europe, exacerbated 
due to TB. The tragic state of affairs reflects a great paradox – that, by the emergence of extensively drug-resistant TB (XDR-TB). MDR-TB is 
despite affordable and effective TB treatment being available for the past uncommon in traditional travellers; however, individual incidents 
seven decades, the latest 2022 WHO Annual Global Tuberculosis Report involving MDR-TB and XDR-TB in airline passengers have been reported 
highlights that TB remains a leading cause of ill health and death from [9–11]. 
an infectious disease worldwide [1]. In 2021, the WHO estimated that In 2006 the WHO published a second edition of tuberculosis and air 
10.6 million people fell sick with TB worldwide: six million men, 3.4 travel: guidelines for prevention and control [12]. That provides infor-
million women and 1.2 million children. Multidrug-resistant TB mation and specific guidance for passengers and crew, physicians, 
(MDR-TB) remains a threat to global health security. Only one in three public health authorities and travel companies, although it now requires 
people with drug-resistant TB can access treatment; many remain un- updating. Every year, millions of people travel to sporting and religious 
diagnosed and untreated. TB today occurs in every part of the world. An events, where mass gathering increases the risk of transmitting a range 
estimated 1 billion people have latent Mtb infection (LTBI), where the of infectious diseases, including TB. The globalisation of 
mycobacteria do not cause clinical disease but serve as a reservoir and antibiotic-resistant bacteria at recurring mass-gathering events is known 
can re-activate at any time under conditions of stress, malnutrition, poor to occur. However, no specific studies have been performed on the 
housing, co-infections and co-morbidities, among other [35]. globalisation of drug-resistant TB due to travel to and from endemic 
Millions of people with active TB continue to suffer, remain undi- countries [13,14]. Such prospective studies are challenging to perform. 
agnosed, and spread both forms of TB –drug-sensitive and drug- Nevertheless, opportunities for developing them often occur [14]. 
resistant. Many of these people travel across the world voluntarily for Millions have had to travel forcibly or voluntarily for several decades 
business or pleasure or are involuntarily forcibly displaced from their across nations and continents due to conflicts, poverty, natural disasters, 
homes and countries due to wars, conflicts, famine, or natural disasters drought, and economic hardships. TB is a known cause of morbidity and 
[2–5]. As the COVID-19 pandemic illustrates, infectious diseases do not mortality among refugees and migrant populations. The past decade has 
respect international boundaries and spread rapidly between countries seen an increase in migration and forced displacement with potential 
and continents. Regional and international travel is no doubt responsible movements of people from high TB burden settings, including MDR-TB, 
for the spread of TB across the world [26]. However, the magnitude of to TB-burdened countries. There appears to be little risk of transmission 
the problem has been challenging to define due to the long incubation of MDR-TB to host populations from migrants to Europe, with more 
period and the insidious and slow progression of clinical disease chance of transmission noted within migrant communities [13]. By 
symptoms and signs. It usually manifests many months or years after the mid-2022, United Nations High Commission for Refugees reports that 
first infection. 103 million people have been forcibly displaced worldwide, including 
https://doi.org/10.1016/j.tmaid.2023.102568 
Received 20 March 2023; Accepted 21 March 2023   
Available online 23 March 2023
1477-8939/© 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
A.J. Rodriguez-Morales et al.                                                                                                                                                         T  r  a v  e l  M   e  d i c  i n  e  a  n  d  I  n f e  c t i o  u  s  D  i s  e a  s e  53 (2023) 102568
53.2 million as internally displaced people and 32.5 million as refugees Conflicts of interests 
[15]. These groups are among the most vulnerable populations at 
increased risk of developing TB [2,4,5]. IA, FN, DYM, NK, OD, PM and AZ acknowledge support from the EU 
Finding and treating new TB cases among these mobile populations is European & Developing Countries Clinical Trials Partnership-funded 
one of the biggest global challenges facing public health systems. Many Pan-African Network for Rapid Research, Response, Relief and Pre-
of them are undocumented, live in poor conditions, with limited access paredness for infectious diseases epidemics (PANDORA-ID-NET), Cen-
to health care and TB services [16,22]. In addition, they may come from tral African Network on Tuberculosis, HIV/AIDS and Malaria (CANTAM- 
weak health systems where trust in the system or access is low [17]. 3), and East African Consortium for Clinical Research (EACCR3) pro-
Ethical screening programs that objectively risk stratification for TB, grammes. IA acknowledges support from a UK NIHR Senior Investigator 
improved screening or diagnostic tools, and optimal management stra- Award and an NIHR Programme Grant (RID-TB). AZ receives a UK Na-
tegies for LTBI are required to avoid stigmatising or ineffective practices. tional Institutes for Health Research Senior Investigator award and is a 
An increasing number of healthcare and humanitarian workers travel to Mahathir Foundation Science Award and Pascoal Mocumbi Prize lau-
work where the incidence of multidrug-resistant tuberculosis (MDR TB) reate. All other authors declare no competing interests. The views 
is high, which may put them at increased risk of infection or developing expressed in this Editorial are entirely those of the authors and do not 
clinical disease. The risk of transmission to them is ever-present due to reflect the opinions of their respective institutions. 
inadequate infection control practices due to lack of respiratory pro-
tection or isolation facilities and the inability to make an early and ac-
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1 Editor-in-Chief, Travel Medicine and Infectious Diseases. 
3