The World Health Organization (WHO) has declared March 24, 2016 as World Tuberculosis (TB) Day [1]. Over the month of March, the Global Health Office will be publishing a series of blog posts about TB in hopes of raising awareness of its worldwide impact. WHO’s “End TB Strategy” has a goal of ending the TB epidemic by 2030, by targeting poverty, improving testing and treatment, ending stigma and discrimination, and driving research and innovation. Put simply, TB is not yet a disease of the past, but if we unite and focus our efforts, we can make TB history.

World TB Day has already passed, but that doesn’t mean the GHO’s March TB blog series is done! There are still a few days left in March, and a few more important aspects of TB to cover. Today, we will be looking at high risk groups for TB infection.

Young children (<5 years old) are more likely to develop TB disease than older children and adults, due to lower immunity. This group is also at a higher risk of developing life-threatening forms of TB disease (e.g., disseminated TB, TB meningitis). TB meningitis occurs when bacteria multiply within the lungs, pass into the bloodstream, and travel into the meninges forming small abscesses. This process causes a rise in pressure within the skull, leading to nerve and brain tissue damage [2].

Persons with medical conditions that weaken the immune system are at an increased risk for TB infection. These conditions include silicosis, diabetes mellitus, head and neck cancers, and most notably, HIV infection [3]. HIV co-infection exacerbates the severity of TB disease, increases the likelihood of progression to TB disease following primary infection or reinfection with TB bacteria, and greatly increases the chances of reactivation of latent TB infection. In fact, people living with HIV are between 26 and 31 times more likely to develop TB disease than persons living without HIV [4].Of the 1.5 million TB deaths worldwide in 2014, 0.4 million occurred among the HIV-positive population. The WHO African Region accounted for 74% of these cases [5].

On the GHO blog, we frequently discuss the social determinants of health. Many of the symptoms of poverty increase the risk of TB infection, but housing may be the most important to consider. In the United States, over 5% of people living with TB reported being homeless within the year prior to their diagnosis. This could be due to a high occurrence of conditions that increase the risk of TB (e.g. substance abuse, HIV infection) in this population, but also due to congregation in crowded shelter conditions [6]. Crowding, and limited air movement within an enclosed space facilitate the spread of M. tuberculosis bacteria. The extent of contact with an infected person also increases the risk of TB transmission, putting frequent visitors to homeless shelters at a higher risk [7]. Living in other locations where close quarters and frequent contact are prevalent, including correctional facilities, also increases the risk of TB infection [8].

We’ve looked at TB on a global scale, but what is the impact of TB in Canada? Find out in our next blog post!