Outside of the public health world it is not widely known that tuberculosis (TB) is the most significant cause of death among persons living with HIV/AIDS (PLWHA), killing one out of three. Since the emergence of the global HIV epidemic in the 1980s, TB has found its niche in the skyrocketing number of persons living with compromised immune systems worldwide. This mutually reinforcing relationship between TB and HIV, the ultimate co-infection, particularly thrives in resource limited settings where access to medical care and health education is restricted. The World Health Organization (WHO) estimates that 50-80% of those infected with TB are also co-infected with HIV in some regions of Sub-Saharan Africa.
Understanding the interaction between these two epidemics is essential for developing effective control strategies to stem transmission. TB is transmitted when an infected person coughs or sneezes infectious TB bacilli into the air and another person inhales these deep into their lungs. After inhalation the body attempts to contain the infection and, if successful, the infection is considered latent and the person is not infectious to others and suffers no TB symptoms. If the body’s immune system is unable to successfully contain the infection, however, the person goes on to have active TB, which is symptomatic and infectious to others. Among those with healthy immune systems, 10% of latent TB infections will become active during the lifetime of the person. This risk is 20-30% greater among PLWHA, making HIV the number one risk factor for active TB disease.
Keeping immune system function high through the use of antiretroviral therapy (ART) for PLWHA can greatly reduce the risk of developing active TB and, additionally, greatly diminish the risk of HIV transmission due to reduced viral loads. However, given the resource-limited settings in which both of these diseases thrive, many of those most at risk are unaware of their HIV status and lack access to these life-sustaining therapies.
The HIV epidemic also plays a notable role in the persistence of dangerous drug resistant strains of TB. Preventing the further transmission of these resistant strains is critical to the prevention of future loss of life from this disease, both for those with compromised immune systems and those who are otherwise healthy. Despite ongoing control efforts, this resistance continues to spread. The development of resistance to antibiotics by pathogens is common, if not expected. It is a process that is constantly occurring, but we can slow it down. In the case of TB, resistance forms when an individual with active TB disease fails to take their entire course of antibiotics and the TB bacteria are not totally eliminated from the body. These surviving bacteria, having been exposure to low levels of antibiotics, are then able to develop protection from the drug, or drugs.
In the case of TB treatment, this frequently occurs because the side effects of the medications used to treat the infection can be severe and the entire course of treatment requires the patient to have access to and diligently take daily medication and even injections over the course of 6 months to several years. No one likes to take medication, particularly something with negative side effects. As such, many infected individuals will stop treatment when they begin to feel well. Other reasons for disuse include infrequent or intermittent access to the drugs or due to adverse reactions when taken alongside ART. These scenarios each lead to the development and spread of drug resistant forms of TB. The HIV epidemic is the ideal vehicle for the spread of drug resistant TB because PLWHA are more at risk for infection and live predominantly in resource-limited settings where access to ART and TB treatment is limited and living conditions are ripe for rapid transmission. In some of these settings, between 18-26% of new cases in PLWHA are drug resistant.
Given the complex nature of this dual epidemic, the design and implementation of effective control and prevention strategies can be both expensive and fraught with complications. Current control strategies heavily rely on finding active and latent cases and providing long-term treatment under the observation of the medical care provider (this is known as directly observed therapy, short-course or, DOTS). Although this method has found clear success, it is both a time intensive and costly because it requires the constant and continued dedication on the part of health organizations, governments, health systems, and funders—which can be dangerous when priorities change before long-term success can be achieved. Additionally, such strategies frequently place a heavy burden on the limited resources and services of vulnerable health systems in the most affected areas.
By understanding and responding to risk factors for diseases like TB, we can supplement the successes of these large-scale control programs and protect against the further spread of drug resistant TB among the most high-risk populations. Risk factors for TB transmission, as a respiratory disease, are very much dependent on environmental conditions like ventilation, temperature, and humidity. As such, the home is a key site where we can devise strategies to reduce transmission risk. ARCHIVE hopes work to find this solution by focusing on improving ventilation within the home. Since 2010, ARCHIVE has been working on a health and housing pilot project aimed at improving health outcomes among PLWHA in the community of Bois L’ Etat, Haiti.
Housing modifications have the unique potential to disrupt the chain of transmission of costly infections that cause high morbidity and mortality without reliance on disease specific medications and long-term treatments with adverse side effects. Additionally, rather than placing greater demand on local healthcare systems, healthy housing functions to independently reduce incidence of costly, easily preventable diseases. Additionally, because many of these simple housing modifications do not require long-term technical education or an advanced degree, the required skills can be developed and fostered within beneficiary communities and then marketed to others. This approach to disease prevention envisions a long-term outcome, rather than a reactionary solution, and acts to supplement more widely used control strategies and diversify our control toolkit with ‘resistance-resistant’ control options. Read more about our house designs and how we are combating TB here!
-Olivia Johns-Yost, Research Officer