Tuberculosis: A global overview of the Situation

 Corresponding author: Rohit G. Nugurwar Copyright © 2025 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution License 4.0. Tuberculosis: A global overview of the Situation Rohit G. Nugurwar 1, *, Neha L. Zod 1, Nikita V. Mahalle 1 and Harigopal S. Sawarkar 2 1 Department of Pharmacology, Dr. Rajendra Gode College of Pharmacy, Amravati-444602, Maharashtra (India). 2 Department of Pharmaceutical Chemistry, Dr. Rajendra Gode College of Pharmacy, Amravati-444602, Maharashtra, India. GSC Biological and Pharmaceutical Sciences, 2025, 33(01), 116-128 Publication history: Received on 03 September 2025; revised on 11 October 2025; accepted on 13 October 2025 Article DOI: https://doi.org/10.30574/gscbps.2025.33.1.0386 Abstract Tuberculosis (TB) continues to be a global health crisis, affecting over 1.7 billion people worldwide by 1990— approximately one-third of the population. This review traces patterns in prevalence, incidence, and mortality, drawing attention to the uneven progress across regions. South-East Asia and China accounted for more than half of global TB cases, while Africa reported the highest incidence rate, averaging 220 cases per 100,000 population. HIV has emerged as a critical driver, contributing to nearly 305,000 additional TB cases and significantly raising mortality, particularly in sub-Saharan Africa. Despite effective short-course chemotherapy and its cost-effectiveness, only about 46% of cases were being detected and treated globally at that time. Mortality remained high, with close to 3 million deaths estimated in 1990, concentrated in South-East Asia, China, and Africa. These findings reflect both medical and socio-economic challenges-ranging from poverty and under nutrition to gaps in health systems. The review emphasizes the urgent need for improved detection, sustained treatment adherence, investment in vaccines and shorter regimens, and strategies that address the social roots of vulnerability. Global elimination of TB will depend not only on medical innovation but also on political will and coordinated international action. Keywords: Tuberculosis; Global burden; Mycobacterium tuberculosis; HIV co-infection; Drug-resistant TB; Incidence; Mortality; Public health; Epidemiology 1. Introduction Tuberculosis (TB) has long been a major cause of illness and death around the world. Yet, for many years, it was largely ignored in both rich and poor countries. Recently, however, TB has started to gain renewed attention, and efforts are being made to strengthen control programs. This renewed focus is mainly due to three reasons[1,5]: •HIV epidemic: TB cases have risen sharply in countries with high HIV infection rates.[1,3,10] •Effective treatment: Short-course chemotherapy has proven to be highly effective in curing TB.[4] •Cost-effectiveness: TB control is recognized as one of the most affordable and efficient public health measures in developing nations.[5] This report provides an update on the global TB situation in 1990, and compares it with trends since 1974. To explain the scale and direction of TB, several key measures are used—such as the ‘prevalence of TB infection, case notification rates, predicted incidence of disease, and TB-related deaths’. The information comes from official reports of TB cases and deaths submitted to WHO, along with estimates based on simple epidemiological models.[14] GSC Biological and Pharmaceutical Sciences, 2025, 33(01), 116-128 117 2. Methods and Data Sources: 2.1. Annual risk of infection and prevalence of infection One of the most important ways to measure TB in a population is by looking at the ‘annual risk of infection-this means the chance that a healthy, uninfected person will get infected with ‘Mycobacterium tuberculosis within one year. This measure is especially useful in countries where TB is common, because it helps estimate how many new TB cases may appear in the future.[6] To calculate this, researchers used data from ‘tuberculin skin test surveys’ that have been collected since 1975. These surveys give information about TB infection at different ages. A model was then applied that considered three main factors:[6] • The annual risk of infection,[6] • How this risk has been changing over time, and [6] • The age structure of the population By combining these factors, they were able to estimate TB infection rates in different regions and age groups.[6] For people with ‘both TB and HIV, estimates were made by applying the TB infection rates in the 15–49 year age group’ (the age group most affected by HIV) to populations where HIV infection is common.[10] 3. Case Notifications Since 1974, the Expanded Programme on Immunization (EPI)has been regularly collecting data on TB cases. These reports are sent by countries or WHO regional offices, and the information is updated and published twice a year. [14] For this analysis, unusual numbers (outliers) were removed. Outliers were defined as cases where the number reported in one year was either three times higher or one-third lower than the numbers reported in the years just before and after. These sharp jumps or drops usually reflect changes in reporting systems or TB programs, not actual changes in the disease itself.[14,11,12] Population figures used as denominators came from World Bank projections, with EPI supplying data for smaller countries.[9] • For each country, researchers calculated:[14,11,12] • The 10-year average number of TB cases (1980–1989), and[14,11,12] • The highest annual number of TB cases reported during the same period.[14,11,12] • To look at longer-term (secular) trends, they examined 5-year averages or the highest annual numbers within those intervals.[14,11,12] For regional figures, the total number of cases reported by all countries in a region was added up. Then, the regional notification rate was calculated by dividing this number by the population of that region (excluding countries that did not report any data).[14,1] 3.1. Expected Incidence To estimate how many new TB cases occur each year, calculations were done separately for each country and then combined at the regional level.[7,8] These calculations were based on two main observations:[7,8] • In countries where TB is very common, for every 1% annual risk of infection, there are about 39–59 cases of smear-positive pulmonary TB per 100,000 people.[7] • For each smear-positive case, there are about 1.22 additional cases of either smear-negative or extrapulmonary TB.[7] Using these relationships, the expected number of TB cases was calculated with different annual risks of infection for different regions:[7,8] GSC Biological and Pharmaceutical Sciences, 2025, 33(01), 116-128 118 • Africa: 1.5% to 2.5%[7,8] • Central & South America + Eastern Mediterranean: 0.5% to 1.5%[7,8] • South-East Asia & Western Pacific: 1% to 2.25%[7,8] On top of this, HIV-related TB was estimated. For people infected with both HIV and TB, it was assumed that about 10% would develop active TB disease each year.[7,8] 3.2. Coverage Coverage (also called the case detection ratio) means the proportion of people with active TB who are actually diagnosed, treated, and officially reported. In practice, this is estimated by comparing the number of reported TB cases with the number of expected cases, and expressing it as a percentage. For 1990, the analysis worked like this:[1,8] The highest, average, and lowest expected numbers of TB cases for each country were calculated by applying the notification rates from 1980–1989 to the 1990 population.[14,1] These figures were then compared with the predicted number of TB cases in 1990, which allowed researchers to estimate a range of coverage values (from low to high) for each country.[1,8] 3.3. Mortality People usually die from tuberculosis when the disease is not diagnosed in time or when treatment does not work— either because patients do not complete their medicines properly or because the TB bacteria are drug-resistant. To measure TB deaths, death certificates are used to see both the total number of deaths and how many of them were caused by TB. For this analysis, mortality data from 62 countries were taken from the World Health Statistics Annual 1988 and 1990.[11,12] The expected number of TB deaths in 1990 was calculated with the following assumptions: • Untreated TB cases: About 50% were expected to die.[11,12] • Treated TB cases: In most developing countries, cure rates are around 50–60%, so the average fatality among reported cases was assumed to be 15%.[11,12] • Although deaths are usually higher among smear-positive patients than smear-negative ones, both groups were assumed to have the same fatality rate, since smear-positive cases are more likely to be identified and treated in developing countries.[11,12] • To estimate mortality, researchers looked at the proportion of patients treated, using both the average and high coverage estimates. This gave a low estimate and a high estimate of TB deaths.[11,12] For TB deaths linked to HIV infection, two different calculations were made:[11,12] • Lower estimate: assumed HIV-positive and HIV-negative TB patients had the same fatality rate and treatment coverage.[11,12] • Higher estimate: assumed that 50% of all HIV-positive TB patients would die, no matter if they were treated or not.[11,12] Finally, countries were grouped by WHO regions (Europe, Eastern Mediterranean, Africa, and South-East Asia). But some adjustments were made:[11,12] China was kept separate because no notification data was available.[11,12] Japan, Australia, New Zealand, Canada, and the USA were also placed in a separate group because they are industrialized countries with very low TB levels.[11,12] As a result, the “American Region” and “Western Pacific Region” in this analysis do not exactly match the official WHO definitions.[11,12] GSC Biological and Pharmaceutical Sciences, 2025, 33(01), 116-128 119 4. Results – Prevalence of Tuberculosis Infection : In 1990, about one-third of the global population—around 1.7 billion people—were infected with Mycobacterium tuberculosis.[1] The Western Pacific Region had the highest infection rate, with 44% of people infected.[1] The Eastern Mediterranean Region had the lowest, at 19%.[1] Most infected people lived in:[1] • South-East Asia (25%)[1] • China (22%)[1] • Europe and five major industrialized countries (22%)[1] 4.1.1. Age distribution of infection: Looking at age patterns shows important differences:[1] • In Western Europe, about 28%of people were infected, but 80% of them were older than 50 years.[1] • In sub-Saharan Africa, about34%were infected, but 77% were younger than 50 years.[1] • In Africa, South-East Asia, and the Western Pacific, more than half of adults aged 15 years and above were infected (54%, 52%, and 62%, respectively).[1] 4.2. Dual infection with TB and HIV:[1,10] In 1990, more than 3 million people worldwide were infected with both TB and HIV.[1] Africa had the largest share, with about 2.4 million people (78% of the total), because HIV levels are very high there and about 48% of adults aged 15–49 already had TB infection.[10] In Europe and the five industrialized countries, over 1.5 million people had HIV, but TB infection was relatively low among 15–49 year olds. As a result, dual TB/HIV infection was rare in these countries-making up less than 6% of the world’s total dual infections.[10] Table 1 Worldwide prevalence of tuberculosis infection, 1990 [1] Region Prevalence (%) Number Infected (Millions) Percentage of total Africa 33.8 171 9.9 America 25.9 117 6.8 Eastern Mediterranean 19.4 52 3.0 South-East Asia 34.3 426 24.7 Western Pacific 43.8 195 11.3 China 33.7 379 22.0 Europe and others 31.6 382 22.2 All Regions 32.8 1722 100 All of the nations in the WHO Region are included. [1] Consists of all nations in the American WHO Region excluding the United States and Canada. [1] All nations in the Western Pacific WHO Region are included with the exception of China Japan Australia and New Zealand. New Zealand. [1] GSC Biological and Pharmaceutical Sciences, 2025, 33(01), 116-128 120 Refers to the USA, Canada, Japan, Australia, and New Zealand.[1] 4.3. Tuberculosis Notifications Country reports[11,12,14,1] Out of 194 countries and states listed in the WHO’s EPI database, 8 countries (about 4%)have not reported any TB cases since 1974. These include:[14] • Africa (3 countries, 6%): Comoros, Namibia, St. Helena[1,11,12,14] • Americas (1 country, 2%): Netherlands Antilles[1,11,12,14] • South-East Asia (1 country, 9%): Democratic People’s Republic of Korea[1,11,12,14] • Western Pacific (1 country, 3%): China[1,11,12,14] • Europe (2 countries, 6%): Albania and San Marino[1,11,12,14] Notifications: Looking at reports from 1980 to 1989, the average number of TB cases reported worldwide each year was about 2.5 million. Around 40%of these were from South-East Asia. The remaining cases were spread almost evenly across the other five regions (each contributing about 8–14%).[1,11,12,14] 4.4. Case notification rates:[14,1] Lowest in industrialized countries about 50 per 100,000 people in Africa and Latin America. The highest annual rat was still modest-about56 per 100,000 in Latin America. [1,11,12,14] Figure 1 Prevalence of tuberculosis infection, by age, in tropical and southern Africa, 1990 GSC Biological and Pharmaceutical Sciences, 2025, 33(01), 116-128 121 Figure 2 Prevalence of tuberculosis infection, by age, in Western Europe 1990.[1] Table 2 Worldwide prevalence of tuberculosis and HIV infection in 15-49 years – olds , 1990.[10] Region HIV Infected(x1000) Prevalence of TB infection HIV/TB infected No.(x1000) % Africa 1500 48 2375 77.8 America 1000 30 301 9.9 Eastern Mediterranean 30 23 7 0.2 South-East Asia, Western Pacific and China 500 40 200 6.6 Europe and others 1500 11 170 5.6 All Region 8030 34 3053 100.0 • This group covers every country in the WHO Region.[1,11,12,14] • This group includes all countries in the Americas, but not the USA or Canada.[1,11,12,14] • This group includes countries in the Western Pacific Region, but not China, Japan, Australia, or New Zealand.[1,11,12,14] • This group only covers the USA, Canada, Japan, Australia, and New Zealand.[1,11,12,14] 4.5. Trends in tuberculosis notifications Between 1974 and 1989, tuberculosis (TB) case reports showed different trends across the world.[14,1] From 1974–79, about 2 million cases were reported (from 178 countries). In the next period, 1980–84, this number rose to 2.4 million (from 180 countries). However, in 1985–89, it fell slightly to 2.2 million (from 164 countries).[14,1] The same general pattern was seen when looking at TB rates per 100,000 people.[14,1] But the story was not the same everywhere:.[14,1] In Europe and other industrialized countries, TB cases kept going down over the 15 years. The sudden rise in 1985–89 was mostly because the USSR started reporting its cases to the WHO in 1988.[14,1] GSC Biological and Pharmaceutical Sciences, 2025, 33(01), 116-128 122 In the Eastern Mediterranean Region and Europe/industrialized countries, TB dropped in both number of cases and infection rates.[14,1] In Africa and South-East Asia, TB increased in both total cases and infection rates.[14,1] In Central/South America and the Western Pacific, infection rates went down, but the total number of cases still went up—likely because populations grew faster than the fall in infection rates.[14,1] Looking at the bigger picture:[14,1] Over 15 years, TB rates decreased in 101 countries but increased in 59 countries (about 1.7 decreases for every 1 increase).[14,1] If Europe and the industrialized countries are left out, the ratio is closer to 1.2 decreases for every 1 increase, suggesting that the global TB situation had not significantly improved in those years.[14,1] Table 3 Mean and highest number of tuberculosis cases reported annually in the world, 1980-89[14,1] Region Mean Highest Cases Rate per 100 000 Cases Rate per 100 000 Africa 234 863 51 317 841 69 Americas 200 607 49 225 815 55 Eastern Mediterranean 361 722 111 602 874 182 South-East Asia 974 861 84 1 223 172 105 Western Pacific 334 205 168 432 846 218 Europe 288 465 34 336 301 40 Others 900 84 21 105 876 25 All Regions 2 484 817 51 3 244 727 68 • Covers every country that belongs to the WHO Region.[14,1] • Refers to all the countries in the Americas, but leaves out the USA and Canada.[14,1] • Refers to the Western Pacific Region countries, but does not include China, Japan, Australia, or New Zealand.[14,1] • Specifically includes only the USA, Canada, Japan, Australia, and New Zealand.[14,1] GSC Biological and Pharmaceutical Sciences, 2025, 33(01), 116-128 123 Table 4 Trends in the average number of tuberculosis cases notified in the world ,1974-89[14,1] Region 1974-1979 1990-1984 1985-1989 Case s Rate per 100 000 populatio n Countrie s reporting (%) Case s Rate per 100 000 populatio n Countrie s reporting (%) Case s Rate per 100 000 populatio n Countrie s reporting (%) Africa 187 084 65 42(91) 230 063 57 43(93) 210 695 57 32(70) Americas 172 220 52 44(94) 203 345 54 44(94) 173 654 42 41(87) Eastern Mediterranea n 274 643 108 23(96) 427 832 143 23(96) 224 302 67 22(92) South-East Asia 696 931 73 10(91) 943 140 87 10(91) 1 023 850 85 10(91) Western Pacific 288 885 174 26(81) 337 907 183 27(84) 304 238 154 26(81) Subtotal 1 617 763 78 145(92) 2 142 287 90 147(94) 1 936 739 72 131(83) Europe 279 905 54 28(88) 179 941 34 28(88) 273 166 33 28(88) Others 132 701 35 5(100) 96 617 25 5(100) 82 224 20 5(100) All Regions 2 032 369 63 178(95) 2 418 845 68 180(93) 2 239 694 58 164(85) 4.6. Impact of HIV on notification rates In Africa, 13 countries with a high number of HIV cases (such as Burundi, Congo, Ethiopia, Kenya, Malawi, Mozambique, Rwanda, Tanzania, Uganda, Zambia, Zimbabwe, Côte d’Ivoire, and Zaire) were compared with other countries in the region. Updated information came from a WHO survey in 1989 and data collected through TB programs supported by the International Union Against Tuberculosis and Lung Disease.[1,10] • Over the last 15 years, a clear difference was seen:[1,10] • In countries without a major HIV epidemic, the average number of TB cases per 100,000 people went down—from 60 (1974–79) to 59 (1980–84) to 47 (1985–89).[14] • In countries hit hard by HIV, TB cases actually went up—from 51 (1974–79) to 56 (1980–84) to 64 (1985–89).[1,10] • This shows that HIV had a major role in pushing TB rates higher in those countries.[1,10] 4.7. Incidence of tuberculosis 4.7.1. Tuberculosis cases in 1990 [1,8] • It was estimated that about 8 million people developed tuberculosis worldwide in 1990. [1,8] • The largest share was in South-East Asia with about 2.47 million cases (31%) [1,8]. • China had around 2.13 million cases (27%) [1,8] • The African Region reported about 1.16 million cases (15%) [1,8] • When looking at how common TB was compared to the size of the population: [1,8] GSC Biological and Pharmaceutical Sciences, 2025, 33(01), 116-128 124 • The highest incidence was in Africa with about 220 cases per 100,000 people. [1,8] • The lowest incidence was in the Americas with around 120 per 100,000 people. [1,8] • In Europe and other industrialized countries, using the average rate from 1980–89 (31 per 100,000), about 392,000 cases were expected in 1990. [1,8] 4.7.2. Effect of HIV on TB cases • HIV greatly influenced TB numbers because people infected with both HIV and TB are more likely to develop active disease. In 1990, the estimated extra TB cases caused by HIV were: [1,10] • 238,000 in Africa[1,10] • 30,000 in Central and South America[1,10] • 20,000 in South-East Asia and the Western Pacific[1,10] • 17,000 in Europe and industrialized countries[1,10] Globally, HIV added about 305,000 TB cases in 1990, which was around 4% of all cases. While this may look small worldwide, in Africa it had a huge effect—raising TB incidence from 220 to 265 cases per 100,000, which is about a 20% increase.[1] Table 5 Cases of tuberculosis expected in the world in 1990[1,8] Region Cases Rate per 100 000 Population Percentage of all cases Africa 1 160 000 220 15 Americas 534 000 120 7 Eastern Mediterranean 594 000 155 7 South-East Asia 2 470 000 194 31 Western Pacific 420 000 191 5 China 2 127 000 191 27 Europe and others 392 000 31 5 HIV-related 305 000 6 4 All Regions 8 002 000 152 100 The annual risk of TB infection was estimated at 1.5–2.5% in Africa, 0.5–1.5% in the Americas and Eastern Mediterranean, and 1–2.25% in South-East Asia and the Western Pacific.[1,10] WHO Region notes:[1,10] • Includes all countries in the WHO Region.[1,10] • For the Americas, this includes all countries except the USA and Canada.[1,10] • For the Western Pacific, this includes all countries except China, Japan, Australia, and New Zealand.[1,10] • The “five industrialized countries” are the USA, Canada, Japan, Australia, and New Zealand.[1,10] HIV-related TB cases by region:[1,10] • Africa: 238,000 cases (78%)[1,10] • Latin America: 30,000 cases (10%)[1,10] • Europe + five industrialized countries: 17,000 cases (6%)[1,10] • Eastern Mediterranean: 693 cases (0.2%)[1,10] • South-East Asia + Western Pacific: 20,000 cases (6%)[1,10]