Reported Tuberculosis in the United States, 2021

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Executive Commentary

Introduction

This 2021 edition of Reported Tuberculosis in the United States reflects a uniquely challenging year for public health and the tuberculosis (TB) community. As with past editions, the report describes information on cases of TB disease reported to the Centers for Disease Control and Prevention (CDC) since 1993. This year’s report emphasizes cases counted by reporting areas in 2021 and the ongoing effects of the COVID-19 pandemic on TB surveillance.

Information in this report summarizes incident cases of TB reported to CDC’s National Tuberculosis Surveillance System (NTSS) by each of the 50 U.S. states and the District of Columbia (D.C.) unless otherwise specified. In addition to the 50 U.S. states and DC, five U.S. territories (American Samoa, Commonwealth of the Northern Mariana Islands, Guam, Puerto Rico, and the U.S. Virgin Islands) and three independent countries that are in compacts of free association with the United States (Federated States of Micronesia, Republic of the Marshall Islands, and Republic of Palau) report incident cases of TB to CDC. NTSS has collected information on all newly reported cases of TB since 1953, and cases reported since 1993 are maintained in an electronic database. Small variations in historical data included in this edition, compared with previous editions, are attributable to updated information submitted in the interim by reporting areas.

Several tables have been reconfigured to effectively and clearly describe trends in TB epidemiology. TB percentages by birth decade cohort were split into separate tables for U.S.-born (Table 8) and non-U.S.–born (Table 9) persons because patterns by birth cohort vary by origin of birth. Tables describing drug resistance by history of previous TB were redesigned into three separate tables: all persons (Table 15), U.S.-born persons (Table 16), and non-U.S.–born persons (Table 17). Tables for social risk factors, including homelessness, residence in a long-term care facility, and substance use, reported by persons with TB were condensed from five distinct tables to one (Table 42). TB cases and percentages by residence in and type of correctional facility by year was added (Table 29).

Overall Trends

In 2021, the United States reported 7,882 TB cases and an incidence rate of 2.4 cases per 100,000 persons, representing a 9.9% increase in case count and 9.8% increase in incidence rate compared with 2020. TB case counts and incidence rates have steadily decreased in the United States since 1992. In 2020, the annual rate of decline was substantially greater than in previous years (Table 1), likely because of factors associated with the COVID-19 pandemic, including a combination of TB underdiagnosis and a true reduction in incidence. TB incidence partially rebounded in 2021, which might be explained by a lessening of the effects of the factors associated with the pandemic, as well as delayed detection of cases with symptom onset during 2020 that were not diagnosed until 2021 because of delayed healthcare access or missed diagnoses. However, TB incidence in 2021 remained 12.4% lower compared with 2019, which might be explained by longer lasting effects of the pandemic, including TB underdiagnosis and public health resource constraints. As the effects of the COVID-19 pandemic shift over time, we must rededicate our efforts and resources to achieve TB elimination in the United States (defined as <1 case per million persons annually).1

The National Vital Statistics System reported 600 TB-related deaths in 2020, the most recent year for which data are available. This is a 14.1% increase from 2019 and is the first time since 2006 that TB-related deaths met or exceeded 600. The mortality rate for 2020 remained 0.2 deaths per 100,000 persons; however, it was 13.0% higher than for 2019 when calculated using unrounded numbers (Table 1).

Nearly half of all U.S. TB cases in 2021 were reported by four states combined: California (22.2%), Texas (12.7%), New York, including New York City (8.7%), and Florida (6.3%). Ten reporting areas had TB incidence rates (cases per 100,000 persons) above the national incidence rate: Alaska (7.9), Hawaii (7.4), New York City (6.2), California (4.5), Delaware (4.1), Texas (3.4), Maryland (3.2), New Jersey (3.2), District of Columbia (2.7), and Washington (2.6). Incidence rates among the U.S. territories and freely associated states ranged from 0.6 (Puerto Rico) to 280.6 (Republic of the Marshall Islands) (Table 34).

Demographics

Origin of Birth

Origin of birth is a prominent risk factor for TB in the United States because of the substantially greater risk of exposure to TB outside of the United States. Since 1993, the number of TB cases and TB incidence rates have declined among both U.S.-born and non-U.S.–born persons. However, those declines in TB have occurred disproportionately among U.S.-born persons, and the percentage of cases that occur among non-U.S.–born persons has increased steadily. In 1993, 29.5% of cases occurred among non-U.S.–born persons, and the incidence rate (cases per 100,000 persons) was 4.6 times higher among non-U.S.–born persons (34.1) than U.S.-born persons (7.4). The year 2001 was the first year that TB cases among non-U.S.–born persons represented more than half (50.4%) of all TB cases, and the incidence rate was 8.7 times higher among non-U.S.–born persons (27.7) than U.S.-born persons (3.2). In 2021, 5,626 (71.4%) cases of TB were reported among non-U.S.–born persons, and 2,223 (28.2%) cases were reported among U.S.-born persons; the incidence rate was 15.8 times higher among non-U.S.–born persons (12.5) than U.S.-born persons (0.8) (Table 10).

Among non-U.S.–born persons with TB in 2021, the most common countries of birth included Mexico (18.7%), the Philippines (12.3%), India (10.2%), Vietnam (7.5%), and China (5.6%) (Table 11). These countries have been the most common countries of birth among non-U.S.–born persons with TB since 2017, and they also represent substantial proportions of the non-U.S.–born population living in the United States.2 Countries of birth with the highest U.S. incidence rates (cases per 100,000 persons from the country population living in the United States) were the Republic of the Marshall Islands (169.6), the Republic of the Congo (101.0), Mongolia (76.9), Bhutan (70.3), Myanmar (70.0), and Somalia (69.6) (Table 12).

Among non-U.S.–born persons with TB, the percentage of cases by years since arrival in the United States decreases over time; the highest percentage of TB diagnoses occurs in the first few years since arrival in the United States. In spite of the reduced TB risk over time, approximately 1/3 of TB cases among non-U.S.–born persons occur 20 or more years after arrival in the United States.3,4 In 2021, the percentage of TB cases among non-U.S.–born persons that occurred within one year of arrival in the United States (9.8%) was similar to 2020 (9.7%), but lower than in 2019 (13.5%) and previous years (Table 13). Also, in 2021 the percentage of cases by time since the person arrived in the United States was 15.4% for 1–4 years, 13.7% for 5–9 years, 9.8% for 10–14, 7.4% for 15–19, 8.5% for 20–24, 6.1% for 25–29, 5.6% for 30–34, 4.2% for 35–39, 9.0% for ≥40 years, and 10.4% for an unknown amount of time (Table 19).

The distribution of TB cases by origin of birth varies by state. States in which at least 85% of cases occurred among non-U.S.–born persons include Idaho (5 cases, 100%), Nebraska (21, 95.5%), Massachusetts (135, 89.4%), Utah (15, 88.2%), New Jersey (254, 87.0%), Wisconsin (57, 86.4%), New York (587, 85.9%), and Washington (171, 85.9%). States in which less than 25% of cases occurred among non-U.S.–born persons include Wyoming (0), Montana (0), Iowa (10, 20.4%), Delaware (9, 22.0%), and Alaska (14, 24.1%) (Table 37).

Race/Ethnicity

The distribution of persons with TB and the TB incidence rates (cases per 100,000 persons) by race/ethnicity were similar to the distribution in previous years and differed by origin of birth (Tables 2–4). Among U.S.-born persons in 2021, the highest percentage of cases occurred among non-Hispanic Black or African American persons (34.1%), followed by non-Hispanic White persons (28.7%), and Hispanic or Latino persons (24.4%). The highest TB incidence rates among U.S.-born persons occurred among non-Hispanic Native Hawaiian or Other Pacific Islander persons (5.7) and non-Hispanic American Indian or Alaska Native persons (3.8) (Table 3).

Among non-U.S.–born persons in 2021, the highest percentage of cases occurred among non-Hispanic Asian persons (48.1%), followed by Hispanic or Latino persons (32.8%) and non-Hispanic Black or African American persons (11.8%). The highest TB incidence rate (cases per 100,000 persons) among non-U.S.–born persons occurred among persons of more than one race/ethnicity (30.2), but small overall population size estimates among persons of more than one race/ethnicity often lead to year-to-year variability in incidence rates. The second highest incidence rates among non-U.S.–born persons occurred among non-Hispanic Asian persons (23.8), followed by non-Hispanic Native Hawaiian or Other Pacific Islander persons (22.0), non-Hispanic Black or African American persons (15.2), Hispanic or Latino persons (8.9), non-Hispanic White persons (3.1), and non-Hispanic American Indian or Alaska Native persons (1.3) (Table 4).

Compared with 2020, TB incidence rates (cases per 100,000 persons) remained steady or increased for all race and ethnic groups except among Native Hawaiian or Other Pacific Islander persons (decreased from 6.2 in 2020 to 5.7 in 2021 for U.S.-born persons and from 35.4 in 2020 to 22.0 in 2021 for non-U.S.–born persons) and non-U.S.–born non-Hispanic Black persons (changed from 15.6 in 2020 to 15.2 in 2021) (Tables 3–4). Small overall population size estimates among Native Hawaiian or Other Pacific Islander persons can lead to year-to-year variability in incidence rates.

Age

TB incidence rates are higher among adults than among children, and among persons 15 years and older, the incidence rates increase with age. In 2021, persons aged ≥65 years had the highest TB incidence rate (cases per 100,000 persons) (4.0), and children aged 5–14 years had the lowest TB incidence rate (0.4). Incidence rates were steady or increased in 2021 compared with 2020 for all age groups except children 0–4 years, which changed from 0.9 in 2020 to 0.8 in 2021. However, compared with 2019, TB incidence rates in 2021 remained the same or lower for each age group (Table 5). Age-specific TB incidence rates among U.S.-born persons ranged from 0.3 for persons 5–14 years to 1.1 for persons 65 years and older (Table 6). Age-specific incidence rates among non-U.S.–born persons ranged from 3.2 for persons 0–4 years to 22.2 for persons 65 years and older (Table 7).

Overall in 2021, 4% of U.S. TB cases occurred among children younger than 15 years of age. The largest percentages of children occurred in Wyoming (1, 33%), Alaska (12, 20.7%), and Arkansas (12, 17.4%) (Table 35). The low number of TB cases in Wyoming led to a large percentage even for a single case in a child.

Sex

In 2021, male persons accounted for 61.3% of TB cases in the United States, including 62.6% of cases among U.S.-born persons and 60.7% of cases among non-U.S.–born persons. Among U.S.-born persons in 2021, the incidence rate (cases per 100,000 persons) for male persons was higher than or the same compared with female persons at every age group. Among non-U.S.–born persons, the incidence rates for female persons were higher at ages 5–14 (4.2) and 0–4 (3.5) years compared with males at those ages (2.3 and 2.9, respectively). For non-U.S.–born persons ≥15 years of age, the incidence rate for male persons was higher compared with females for each age group; the incidence rate for male persons 65 years and older (31.4) was double the incidence rate for female persons 65 years and older (15.0) (Table 27).

Clinical Characteristics

Primary Reason for Tuberculosis Evaluation

Similar to past years, experiencing TB symptoms was the primary reason for TB evaluation for the majority (55.7%) of U.S. TB cases in 2021. Active case-finding methods, including investigation of close contacts to an infectious TB case and planned screening or “targeted testing” of groups expected to have elevated prevalence of TB infection, were reported as the primary reason for TB evaluation for 13.8% of TB cases (Table 40), an increase compared with 9.5% of 2020 cases.5

Case Verification Criteria

U.S. TB cases are verified based on the following laboratory testing hierarchy: positive culture, positive nucleic acid amplification (NAA) test (when culture results are unavailable or negative), or positive acid-fast bacilli (AFB) smear (when culture or NAA test results are unavailable or negative). For example, cases that were initially verified using NAA tests but subsequently confirmed via positive culture are reported as verified by culture. TB cases may also be verified using prespecified clinical criteria for cases not able to be verified through laboratory testing (Appendix A). Additionally, CDC will accept and count TB case reports based on a healthcare provider’s diagnosis of TB disease (provider diagnosis), even if the case does not otherwise meet the national surveillance case definition for TB (Appendix B).

In 2021, 79.2% of TB cases were verified through positive culture, consistent with previous years in which the majority of U.S. TB cases have been verified through positive culture. Cases that are verified by positive NAA test have increased from 0.5% in 2009 to 3.0% in 2021 but continue to account for a small percentage of all TB cases. Likewise, cases verified by positive AFB smear continue to account for a small percentage (0.3%) of TB cases in 2021. In 2021, 13.1% of cases were verified based on the prespecified clinical criteria in the national surveillance case definition, and 4.4% were reported based on provider diagnosis alone (Table 14).

Site of Disease

TB most commonly affects the lungs but can cause disease in any part of the body. Similar to previous years, 78.8% of U.S. TB cases had pulmonary involvement (Table 14). Among the 21.2% of U.S. TB cases with only extrapulmonary TB, the most common sites affected were the lymphatic system (30.6%) and pleura (15.2%) (Table 14 and 23). Bone and joint TB increased from 143 (8.9%) cases in 2020 to 243 (13.7%) cases in 2021, including 113 cases associated with a large outbreak linked to a bone allograft product (Table 23).6 TB meningitis, a particularly serious form of the disease, accounted for 3.5% of extrapulmonary-only cases (Table 23).

TB Treatment and Drug Resistance

Effective TB treatment includes providing multiple anti-TB drugs over a sufficient period of time to cure the patient, prevent development of drug resistance, and minimize the risk of transmission to others. The most common initial treatment regimen for drug-susceptible TB, and in situations where drug-susceptibility is unknown, includes isoniazid, H; rifampin, R; pyrazinamide, Z; and ethambutol, E (HRZE).7

Since 2002, more than 80% of persons with TB who were alive at diagnosis and had initial drug regimen information began treatment with HRZE. Among persons with TB who were alive at diagnosis and had initial drug regimen information in 2021, 83.2% began treatment with HRZE, 10.4% began treatment with a four-drug regimen other than HRZE, 0.9% received no initial drug therapy, and 0.3% were started on one drug (Table 18). Four-drug initial regimens other than HRZE can be clinically appropriate if resistance or one of more of the drugs in the HRZE regimens is known or suspected, or if there are other clinical contraindications to using HRZE. Accordingly, the vast majority (93.7%) of TB patients alive at diagnosis reported in the United States are likely to have received appropriate initial TB therapy.

Anti-TB drug resistance is a concern in the United States and globally. Resistance to isoniazid, one of the most common anti-TB drugs, can be a precursor to multidrug-resistant (MDR) TB, which is defined as resistance to at least isoniazid and rifampin. In 2021, CDC adopted new definitions of extensively drug-resistant (XDR) and pre-XDR TB. Pre-XDR TB is caused by an organism that is resistant to isoniazid, rifampin, and a fluoroquinolone or by an organism that is resistant to isoniazid, rifampin, and a second-line injectable (amikacin, capreomycin, and kanamycin). XDR TB is caused by an organism that is resistant to isoniazid, rifampin, a fluroquinolone, and a second-line injectable (amikacin, capreomycin, and kanamycin) or by an organism that is resistant to isoniazid, rifampin, a fluoroquinolone, and bedaquiline or linezolid.8

During 2021, isoniazid resistance at initial diagnosis was reported for 536 (8.9%) cases in the United States, including 5.8% of cases among U.S.-born persons and 10.0% of cases among non-U.S.–born persons. MDR TB at initial diagnosis was reported for 77 (1.3%) cases, including 11 (0.7%) cases among U.S.-born persons and 66 (1.5%) cases among non-U.S.–born persons (Table 15–17). Drug resistance is more commonly observed among persons who have previously been diagnosed with TB. Among persons diagnosed with TB in 2021 who had a previous TB diagnosis, 13.9% had INH-resistant TB and 4.6% had MDR TB. Among persons diagnosed with TB in 2021 who reported no previous TB diagnosis, 8.7% had INH-resistant TB and 1.2% had MDR TB (Table 15).

Pre-XDR and XDR TB continue to be rare in the United States, with four cases of pre-XDR TB and two additional cases of XDR TB in 2021. Stringent guidelines for TB treatment in the United States, including diligent follow-up efforts by public health personnel, greatly reduce the risk of developing drug-resistant TB.

Directly Observed Therapy and Completion of Treatment

Directly observed therapy (DOT) involves direct observation by a trained individual of a patient ingesting anti-TB medications to ensure patients adhere to their prescribed therapy. DOT is a critical case management strategy to achieve completion of TB therapy, helping prevent TB from spreading to others and avoiding development of drug-resistant TB. For cases reported in 2019, the most recent year for which data are available, TB treatment was administered using exclusively DOT for 62.2% of patients, and 33.0% received TB treatment with a combination of DOT and self-administered therapy (Table 18).

Successful completion of TB treatment is important to prevent TB recurrence and drug resistance. TB treatment completion remained relatively steady for cases reported in 2019, the most recent year for which data are available. Among all persons diagnosed with TB during 2019 who were alive at diagnosis and taking one or more TB medications, 86.8% completed treatment (Table 20). Reasons for not completing treatment include the patient dying before treatment could be completed (7.5%), loss to follow-up before documenting completion of treatment (1.5%), patient deciding to discontinue treatment prior to completion against medical advice (i.e., refusal) (1.1%), stopping TB treatment because of an adverse treatment event (0.3%), and other or unknown/unreported reasons (2.8%) (Table 20). An uncomplicated course of treatment for drug-susceptible TB takes about 6 months to complete; however, drug resistance or other factors can require treatment for >1 year. Among 2019 patients eligible to complete TB treatment within 1 year, 89.9% completed treatment within 1 year and 95.5% ever completed TB treatment (Table 18).

Risk Factors

Comorbid Conditions

Medical conditions or therapies that weaken or suppress the immune system can increase the risk for TB. Diabetes mellitus (23.9%) remains the most commonly reported medical risk factor among persons with TB and was reported by a larger percentage of non-U.S.–born persons with TB (26.7%) compared with U.S.-born persons with TB (16.8%) (Table 28). Among persons with TB in 2021 who were alive at diagnosis, human immunodeficiency virus (HIV) status was known for 90.5%, and 4.2% of persons with TB and known HIV status were coinfected with HIV (Table 19). Tumor necrosis factor-alpha (TNF-α) antagonist therapy was reported for 1.0% of cases, and 0.7% of persons had received a solid organ transplant. Other immunocompromising conditions or therapies were reported for 8.6% of cases (Table 28).

Persons who have been recently infected with Mycobacterium tuberculosis are also at increased risk for developing TB disease compared with persons exposed in the past. Having been a known contact of a person with infectious TB within the last two years was reported for 6.1% of cases in 2021 compared with 7.4% for 2020. In 2021, 12.0% of U.S.-born persons with TB and 3.7% of non-U.S.–born persons with TB (Table 28) were known contacts of a person with infectious TB.

Congregate Settings

Living in congregate settings, including homeless shelters, correctional facilities, and long-term–care facilities, is a risk factor for TB because shared airspace can facilitate TB exposure and transmission. Among persons aged ≥15 years with TB in 2021, 341 (4.5%) reported experiencing homelessness within the 12 months preceding TB diagnosis (Table 42). This compares with 290 (4.3%) TB cases in 2020 among persons aged ≥15 years with reported homelessness in the past year.5

Among persons aged ≥15 years with TB in 2021, 179 (2.4%) cases occurred in current residents of correctional facilities; of those, 12.3% occurred in residents of federal prisons, 27.9% in residents of state prisons, 31.3% in residents of local jails, 0.6% in residents of juvenile correctional facilities, and 27.4% in residents of other correctional facilities (Table 41).

During 2021, 109 (1.5%) TB cases were diagnosed among current residents of long-term–care facilities aged ≥15 years (Table 42).

Substance Use

Substance use is also a TB risk factor. The most commonly reported type of substance use during the year preceding diagnosis among persons with TB aged ≥15 years was excess alcohol use (8.2%), followed by noninjecting drug use (7.0%), and injecting drug use (1.1%) (Table 42).

Case Outcome

Among all TB cases diagnosed during 2019, a total of 892 (10.0%) persons died, with 313 (35.1%) of those deaths attributed to TB disease or TB treatment. Of the 892 deaths, 221 (24.8%) persons were dead at the time of TB diagnosis; 29.0% of those deaths were attributed to TB. The remaining 671 (75.2%) deaths occurred after diagnosis, of which 37.1% were attributed to TB (Table 21).

Conversion of a patient’s positive sputum culture to negative is an indicator of treatment effectiveness. Among 5,047 cases during 2019 with positive sputum cultures, 4,394 (87.1%) had documented sputum culture conversion to negative. Among the 612 (12.1%) cases for which sputum culture conversion was undocumented, the most common reason was that the patient had died (250, 40.8%) before sputum culture conversion (Table 22).

Molecular Surveillance

Genotype Clusters

TB genotyping is a laboratory-based approach used to analyze genetic material (e.g., DNA) of Mycobacterium tuberculosis; characterizing distinct genetic patterns facilitates distinguishing certain M. tuberculosis strains from others. Conventional genotyping combines the results of spoligotyping and mycobacterial interspersed repetitive unit-variable number tandem repeats (MIRU-VNTR); isolates with matching spoligotype and MIRU-VNTR patterns are assigned the same genotype. For reporting purposes, a TB case is considered clustered if its isolate genotype matched one or more cases in the same county or county-equivalent area during the 3-year period of 2019–2021. Clustered TB cases are an indication of possible recent TB transmission. CDC generates cluster alerts (i.e., medium alert and high alert) based on the degree of geospatial concentration of cases with matching genotypes within the same county or county-equivalent area compared with the concentration of the genotype outside of the given county or county-equivalent. CDC reviews medium and high alerts weekly for possible programmatic follow-up.

The number of reported TB cases with a genotype rose from 5,586 in 2020 to 6,075 in 2021 (Table 24), an 8.8% increase mirroring the national case count increase (Table 1). Since 2015, over 97% of culture-positive cases in the United States have been genotyped annually (Table 24). During 2019–2021, 19.2% of TB cases were clustered (Table 30). The number of county-based GENType clusters declined from 1,280 in last year’s report5 among cases reported nationally during 2018–2020 to 1,241 clusters for the 2019–2021 time period. The number of larger clusters (i.e., clusters with 6 or more cases) decreased from 79 during 2018–2020 to 74 during 2019–2021 (Table 31).5

Cases occurring in certain demographic groups continue to be overrepresented in genotype matched clusters and alerted clusters. Among cases occurring in U.S.-born persons, 34.6% were clustered compared with 13.5% of cases occurring in non-U.S.–born persons; 54.7% of clustered cases occurring in U.S.-born persons were in medium or high alert clusters compared with 22.9% of cases occurring in non-U.S.–born persons (Table 30). Among all cases associated with a cluster during 2019–2021, cases occurring in Hispanic or Latino persons (n=1,277), non-Hispanic Black or African American persons (n=880), and non-Hispanic Asian persons (n=810) accounted for >83%. However, within race/ethnicity, over 50% of cases occurring in non-Hispanic American Indian or Alaska Native persons and non-Hispanic Native Hawaiian or Other Pacific Islander persons were clustered (Table 30).

During 2019–2021, 38.3% of clustered cases were included in clusters that were classified as either medium or high alert (Table 30). The percentage of persons representing clustered cases diagnosed while in a correctional facility that were in high alert clusters was 36.4% during 2018–20205 compared with 42.1% during 2019-2021.

Estimates of Recent Transmission

CDC uses data from conventional genotyping to estimate the number and percentage of TB cases that are attributed to recent transmission. Estimates are based on whether a TB case has a plausible source case with a matching genotype in a person who resides within ten miles and was diagnosed with TB within two years before the diagnosis of the person whose TB case is being evaluated for recent transmission; if there is a plausible source case with these parameters, the case is attributed to recent transmission.9 Cases that are attributed to recent transmission are further assessed for whether they belong to a plausible chain of transmission of ≥6 cases within a 3-year time period. If so, the case is additionally considered to be attributed to extensive recent transmission.

The number of cases attributed to recent transmission declined from 1,703 before the emergence of the COVID-19 pandemic (i.e., 2018–2019) to 1,400 during 2020–2021 and the number attributed to extensive recent transmission decreased from 557 to 456.3 However, the percentages of cases attributed to recent and extensive recent transmission were similar between these 2-year periods (12.5% and 4.1% versus 12.3% and 4.0%, respectively) (Table 54).3 While estimates of recent transmission vary across the 52 U.S. reporting areas, all but seven areas had at least one case during 2020–2021 that was attributed to recent transmission (Table 52). Of all counties during 2018–2019 and 2020–2021 with >5% of cases attributed to extensive recent transmission, 29 counties were common to both 2-year periods (Table 53).3

Although 71.4% of reported TB cases were among non-U.S.–born persons during 2020–2021 (Table 10), 53.6% of cases attributed to recent transmission and 59.0% of cases attributed to extensive recent transmission were among U.S.-born persons (Table 54). Notably, the percentages of cases in some populations at increased risk for TB that were attributed to recent transmission and extensive recent transmission have increased during 2020–2021 compared with 2018–2019. Among persons residing in a correctional facility at the time of TB diagnosis during 2020–2021, 26.7% and 18.0% of cases were attributed to recent transmission and extensive recent transmission, respectively, compared with 18.1% and 10.4% in the previous 2-year period. Among non-Hispanic Native Hawaiian or Other Pacific Islander persons, the percentage of cases attributed to recent and extensive recent transmission increased the most among all race/ethnicity populations, from 32.3% and 12.3%, respectively, during 2018–2019 to 35.4% and 17.1% during 2020–2021.3 The highest percentages for both recent and extensive recent transmission in 2020–2021 were observed among non-Hispanic American Indian or Alaska Native persons (41.6% and 18.4%, respectively) (Table 54).

Recent and extensive recent transmission estimates for persons experiencing homelessness in the year prior to TB diagnosis were higher than the overall national estimates during 2020–2021 (27.1% and 13.0%, respectively) (Table 54). However, recent transmission estimates among persons experiencing homelessness has declined since 2018–2019 (30.9%) and extensive recent transmission estimates are similar compared with 2018–2019 (13.4%).3 Recent transmission estimates among children aged 5–14 years were 23.1% during 2020–2021, compared with 33.3% during 2018–2019. Extensive recent transmission estimates among children aged 5–14 years were 6.8% during 2020–2021, compared with 9.5% during 2018–2019.3

Conclusion

In 2021, reported TB cases and incidence rates in the United States increased compared with 2020 but remained substantially lower than 2019. The first year of the COVID-19 pandemic caused drastic changes in immigration and travel, health care and public health services, social exposures, and mortality, which likely led to a combination of TB underdiagnosis and a true reduction in TB incidence in the United States. In 2021, the partial rebound in TB incidence in the United States is likely explained by many of the same factors that affected TB incidence in 2020, but to a lesser degree, combined with increased diagnoses of TB for which symptoms began in 2020 but were not detected until 2021.

In 2021, an increase in TB incidence rate was seen for both U.S.-born and non-U.S.–born persons. The increase in incidence rate from 2020 to 2021 was 11% among the U.S.-born population compared with 7% among the non-U.S.–born population. The majority of TB cases continue to occur among non-U.S.–born persons, and more than one quarter of cases among non-U.S.–born persons occurred within five years of arrival in the United States.

The percentage of cases attributed to recent and extensive recent transmission has remained steady, suggesting that the COVID-19 pandemic did not affect recent transmission overall. Non-Hispanic American Indian or Alaska Native, non-Hispanic Native Hawaiian or other Pacific Islander, and non-Hispanic Black or African American populations, persons experiencing homelessness or who use substances, and persons diagnosed while in correctional facilities continue to be disproportionately represented in genotype clusters and have higher estimates of recent transmission.

Even though <15% of U.S. TB cases are estimated to be attributed to recent transmission and large outbreaks of TB are uncommon, outbreaks remain a public health concern.5,10,11 In 2021, an outbreak linked to a donor-derived bone allograft product was associated with 113 cases in 18 states. Cases in this outbreak were predominately among U.S.-born persons,6 and might have contributed to the 11% increase in incidence rate among U.S.-born persons. In Delaware, where the outbreak was first detected,12 TB incidence (cases per 100,000 persons) more than doubled, from 1.7 in 2020 to 4.7 in 2021. TB is primarily transmitted through the air; <1% of U.S. TB cases are associated with solid organ transplantation, and transmission through transplanted tissues is rare. This is the first known outbreak associated with transplanted tissue. The percentage of cases with bone or joint as the site of disease was 8.9% in 2020, compared with 13.7% in 2021.

Globally in 2021, TB was the second leading cause of death from a single infectious agent, surpassed only by COVID-19.13 TB is preventable and treatable, and TB-related deaths are less frequent in the United States compared with global TB mortality.5,13 However, the 14% increase in TB-related deaths in 2020 is concerning, especially in a year that experienced a 19% decline in TB cases. TB-related deaths also increased globally in 2020, but the reasons for the increase are not clear. Natural year-to-year variability could explain some of the increase in TB-related deaths. Other contributing factors might relate to the COVID-19 pandemic, including delayed diagnosis and disruption to TB and other healthcare services that resulted in poorer outcomes. Similar to HIV coinfection, coinfection with SARS-CoV-2 might also have increased the risk of death among persons with TB.

The effects of the COVID-19 pandemic on TB epidemiology are complex and will likely persist for many years. In spite of the setbacks created by the COVID-19 pandemic, CDC remains dedicated to reducing TB morbidity, mortality, and disparities. CDC is committed to regaining momentum lost because of the COVID-19 pandemic and to achieving TB elimination through timely and complete TB diagnosis and treatment and other essential TB prevention activities.

References
  1. Centers for Disease Control and Prevention. Division of Tuberculosis Elimination Strategic Plan 2016-2020. Accessed July 30, 2020. https://www.cdc.gov/tb/about/strategicplan.htm
  2. U.S. Census Bureau. Public Use Microdata Sample (PUMS) documentation. Accessed November 14, 2019. https://www.census.gov/programs-surveys/acs/microdata/documentation.2019.html
  3. Centers for Disease Control and Prevention. Reported Tuberculosis in the United States, 2019. Accessed August 3, 2021. https://www.cdc.gov/tb/statistics/reports/2019/default.htm
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