Opinion: Myth busting 5 tuberculosis misconceptions on World TB Day

It is time to get back to basics on tuberculosis: revisit established facts about the epidemiology of this communicable disease, examine new evidence-based strategies to end TB, and bust long-standing misconceptions and myths about the disease. We are not on track to achieve the goals of End TB goals by 2030 or 2035. Indeed, for the first time in many years, there has been an increase in the number of people falling ill with TB — 10.6 million in 2021 — and a rise in deaths, with 1.6 million dying in 2021. We have the tools to find, cure, and prevent TB, but we need to deploy them more effectively. We need to recall that everyone who develops TB has been infected by someone else in their household, workplace, or community who has untreated infectious TB. In countries where TB is very common — high-burden countries — most people who develop TB have been infected, or sometimes reinfected, recently (in the preceding two years). Hence, finding and treating everyone in a locality who has infectious TB is the key to preventing TB. This approach, known as active case-finding, breaks the chain of transmission and turns off the tap for TB. If fewer people develop TB because they are not infected, even fewer people will develop TB infection in the future. In this way, the benefits of active case-finding accelerate over time. Unfortunately, this simple strategy, which was the basis of campaigns to end TB in high-income countries in Europe, North America, Japan, and Australia in the 1950s to 1970s, has been deemed too expensive, resource intensive, and difficult to implement in high-burden countries. Here are some facts about this strategy, which my colleagues and I implemented in a proof-of-concept cluster randomized controlled trial in Vietnam. We have put together an extensive list to dispel the myths, misconceptions, and half-truths getting in the way of ending TB. Here are five of the most harmful: Myth 1: We need to focus on high-risk groups to end TB in high-burden settings. In fact, most people who develop TB in high-burden TB countries are not members of high-risk groups, such as household contacts, people living with HIV, people with diabetes, homeless people, and people in prison. In most settings, these groups represent a small minority of the population — except for people living with HIV in some sub-Saharan African settings. Even if these groups have a higher risk of having TB than others, the number of high-risk people detected with TB will almost always represent a small proportion of all the people with TB. Hence, while focusing on high-risk groups is beneficial for the members of those groups with TB, it will not be sufficient to end TB in high-burden settings. Myth 2: Active case-finding for TB is mainly for the benefit of people who are diagnosed with TB. People with undiagnosed TB are at risk of death or severe long-term disability, so finding and treating them is to their benefit. However, unlike non-communicable diseases such as cancer, hypertension, metabolic diseases, the benefit doesn’t end with the person with TB who is found and treated. Indeed, the main rationale for active case-finding is to prevent infection of others by finding and treating people with infectious disease. Myth 3: Even if we find all currently infectious people and prevent all new infections, we can never end TB while there are nearly 2 billion people with latent TB infection. There are indeed many people with latent TB infection, that is people who have TB infection but do not currently manifest any evidence of disease. Although it cannot be directly measured, immunological tests are able to detect probable latent TB infection in 30-50% of adults in high-burden settings. Most of these people have never been treated and we know from observations of people living with HIV and people treated with potent immunosuppressive drugs that the infection is highly likely to reactivate if the immune system is disrupted in a specific manner — that is, people will develop active TB disease. However, we also know from studies in low-burden TB settings that, in the absence of these specific triggers, the rate of reactivation of latent TB infection acquired in the remote past (more than 2-3 years) is lower than in those recently infected. In these settings, this low rate of reactivation has not led to a resurgence of TB transmission, even in the absence of widespread treatment of latent TB infection. In high-burden settings, reactivation of remote past latent TB infection represents a small proportion of all incidences of active TB. Therefore, it probably will not undermine the benefits of active case finding in transforming high-burden to low-burden settings. Myth 4: Active case-finding is active case-finding; it doesn’t matter how you do it, it all helps end TB. As mentioned earlier, we need to find and treat all, or nearly all, people with active pulmonary TB disease in a geographically defined locality in order to break the TB epidemic chain. This goal can only be achieved if active case-finding is implemented as follows: • All people, including older children and adults, in the geographically defined locality are screened, not just those in high-risk groups, those who volunteer, or those with symptoms. • The first-stage screening test has high sensitivity for TB, that is, it does not miss many people with TB. • All confirmed people with TB should receive and complete appropriate and effective TB drug therapy. • The active case-finding intervention must be repeated regularly — say, annually — until the number of people with TB is very low and the cycle of ongoing infection and disease is broken. This may take five to 15 years, depending on how many people have TB when you start and how effective the active case-finding program is. Myth 5: The cost per person detected in community-wide active case-finding is high. Therefore, the intervention cannot be considered cost-effective compared with other interventions. This would be correct if TB was a noncommunicable disease, in which the only beneficiaries are the people diagnosed with it. However, calculating the number of people needed to be screened to detect a single person with TB — the yield — is the wrong measure to gauge the value of active case-finding for TB. This measure completely discounts or ignores the prevention benefits of finding and treating people with infectious TB. The goal is to end TB by breaking the chain of transmission. The relevant endpoint is the impact on the incidence of TB. The number of people with TB who remain undetected, rather than the number of people detected with TB, is a more relevant intermediate endpoint. Visit the Talking TB series for more coverage on how we can eliminate tuberculosis by 2030. The time for a paradigm shift and a renewed focus on funding, research, and global solutions is now. Join the conversation by using the hashtag #TalkingTB.