infectious diseases
Tuberculosis (TB)
Epidemiology of TB
Based on tuberculin skin testing surveys, it is estimated that about one fourth of the world’s population is infected. Of those infected, perhaps 15 million have active disease at any given time. In 2020, an estimated 9.9 million (127/100,000) new tuberculosis cases occurred worldwide. Most new cases occurred in Southeast Asia (43%), Africa (25%), and the Western Pacific (18%) ( Epidemiology references . Case rates vary widely by country, age, race, sex, and socioeconomic status. In 2020, two thirds of new cases occurred in 8 countries; most occurred in India (26%), followed by Indonesia (8.4%), China (8.5%), the Philippines (6.0%), Pakistan (5.8%), Nigeria (4.6%), Bangladesh (3.6%), and South Africa (3.3%) ( Epidemiology references ). A few countries, including North Korea, Lesotho, Mozambique, the Philippines, and South Africa, had incidence rates above 500/100,000 ( Globally, drug-susceptible TB incidence and mortality are slowly decreasing. The cumulative reduction from 2015 to 2019 was 9% (from 142 to 130 new cases per 100,000), including a reduction of 2.3% between 2018 and 2019. These trends are likely due in part to global TB control efforts that have provided more people with access to drugs for TB and HIV infections. However, the 2020 to 2021 global COVID-19 pandemic disrupted other public health programs, including TB control, and although it is too soon to quantify, the WHO predicts a stalling or reversal of these decreasing global trends ( Epidemiology references ). In the US in 2021, 7860 new cases of TB were reported to the CDC for a case rate of 2.4/100,000 ( Epidemiology references ). During the COVID-19 pandemic in 2020, there was a 20% decrease from 2019 rates ( A resurgence of TB occurred in parts of the US and other economically advanced countries between 1985 and 1992; it was associated with several factors, including HIV coinfection, homelessness, a deteriorated public health infrastructure, and the appearance of multidrug-resistant TB (MDR-TB, defined as resistance to at leastisoniazidandrifampin). MDR-TB andrifampin-resistant TB (MDR/RR-TB) have been substantially controlled in the US by effective public health and institutional infection control measures, but until recently, infection caused by these organisms had been increasing around the world. However, the incidence appears to be slowly decreasing worldwide. Decreasing TB incidence and improved (molecular) diagnostics, treatment, and case management of drug-sensitive and drug-resistant TB are the likely explanations. Although MDR/RR-TB cases make up less than 4% of incident cases, the diagnosis and treatment of these cases consume a disproportionate fraction of TB control resources. MDR/RR-TB results in a disproportionate share of human suffering, death, and economic consequences for impacted people and their families. Still, in many parts of the world, MDR/RR-TB cannot be rapidly diagnosed and promptly treated with effective regimens, including effective management of adverse effects of second-line drugs. This situation results in ongoing transmission, low cure rates, and amplified resistance. Treatment of highly drug-resistant TB cases has had even less favorable outcomes, including high mortality rates, especially in patients coinfected with HIV, even when they are being treated with antiretroviral drugs. Newer, shorter, more effective (noninjectable) treatment regimens combined with adverse effect management, community outreach, and social support have resulted in more favorable downward epidemiologic trends for drug-resistant TB globally, especially in a few areas (eg, Peru, the Tomsk region of Russia). India and China are implementing countrywide MDR-TB programs, and the future of MDR-TB may be greatly influenced by the success or failure of these programs. 1.World Health Organization (WHO): Global Tuberculosis Report 2021. Accessed on 4/17/2022. 2.Centers for Disease Control and Prevention (CDC): Tuberculosis—Data and Statistics. Accessed on 4/19/2022. 3.Deutsch-Feldman M, Pratt RH, Price SF, et al: Tuberculosis—United States, 2020.MMWR Morb Mortal Wkly Rep70:409–414, 2021. doi: 10.15585/mmwr.mm7012a1 