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Tuberculosis control branch

Tuberculosis in California: 2023 Snapshot 

Tuberculosis disease (TB) is an illness caused by the bacteria Mycobacterium tuberculosis. TB usually affects the lungs and spreads through the air when a person sick with TB coughs. Not everyone infected with the bacteria becomes sick. People that have been infected but are not sick have latent tuberculosis infection (LTBI). People with LTBI can become sick with TB disease in the future if they do not take treatment for LTBI.​​

TB cases in California have increased 24% since 2020​​

Reported TB Cases in California from 2014 to 2023

  • In 2023, 2,113 new TB cases were reported, a substantial increase (15%) compared with 1,842 in 2022.
  • California's annual TB incidence was 5.4 cases per 100,000 persons.
  • Since 2020, TB cases in California have been increasing each year for a total increase of 24% over the last ​​four years, returning to case numbers not seen since before the COVID-19 pandemic.​
  • Potential reasons for the increase include resumption of normal activities that had been reduced at the start of the COVID-19 pandemic and which may have temporarily reduced TB transmission and TB detection.  Travel and migration between California and elevated TB areas have resumed. People may have returned to seeking health care normally and providers and public health programs are again testing for TB and LTBI. Less TB prevention and contact investigation during the pandemic likely increased the number of people with untreated LTBI who may have progressed to active TB disease. Persistent insufficient LTBI testing and treatment coupled with above factors are likely responsible for the overall TB case increase.
  • TB cases were reported in 45 (74%) of California's 61 local health jurisdictions (LHJs); 21 (34%) LHJs reported 1–9 cases. More than one third of LHJs that reported at least 10 cases of TB in 2023 had a single year increase of more than 20%. 
  • The vast majority of TB cases (85%) were attributable to progression of LTBI to active TB, while an estimated 5% of cases were in persons who arrived in California from outside the United States with active TB disease, and another 10% resulted from recent transmission.
  • In 2023, there were 8 new TB outbreaks and 13 ongoing outbreaks in 14 jurisdictions, each involving at least 4 persons.
  • More than 2 million Californians (6%​ of the population) have LTBI. Without treatment LTBI can progress to active TB.
  • Medical and societal costs of TB reached $265 million in California in 2023.*

* Costs calculated using data from Oh et al. and methods from Castro et al. Oh P, Pascopella L, Barry PM, Flood JM. A systematic synthesis of direct costs to treat and manage tuberculosis disease applied to California, 2015. BMC Res Notes. 2017;10(1):434. Published 2017 Aug 30. doi:10.1186/s13104-017-2754-y.

Castro KG, Marks SM, Chen MP, et al. Estimating tuberculosis cases and their economic costs averted in the United States over the past two decades. Int J Tuberc Lung Dis. 2016;20(7):926-933. doi:10.5588/ijtld.15.1001

TB kills more than 200 Californians ​each year

  • The percentage of people with TB who die has been increasing. In 2010, 8.4% of people with TB died. In 2020 this percentage reached a peak of 13%.  In 2021, 217 (12% of TB cases) people with TB died; of those, 61 (28%) died before receiving treatment for TB.​

People born outside the United States bear the largest burden of TB

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  • The TB rate among people born outside the U.S. (16.6 per 100,000) was 13 times higher than the rate among U.S.-born persons (1.3 per 100,000).

  • Nearly half of cases in people born outside the U.S. occurred more than 20 years after U.S. arrival.

  • Among the 5 most frequent countries of birth outside of the U.S., the TB rate was highest among people born in the Philippines (47.3 per 100,000) and Vietnam (36.6 per 100,000), followed by India (20.6 per 100,000), China (14.8 per 100,000) and Mexico (11.8 per 100,000).

There are severe disparities by race, ethnicity, and place of birth

TB Incidence Rates by Birthplace, Race, and Ethnicity, California 2023

  • Nearly half (47%) of California's TB cases occurred in Asian* persons, and 40% of cases occurred in Hispanic persons.
  • Rates of TB among people born outside the U.S. who are non-Hispanic Asian, non-Hispanic Black, or Hispanic were many times higher than non-Hispanic White people born in the U.S.
  • In each racial and ethnic group, TB rates were higher in non-U.S.-born than U.S.-born people. Among U.S.-born people, non-Hispanic Asian, non-Hispanic Black, and Hispanic persons had higher rates than non-Hispanic White persons.

Diabetes and other conditions that increase TB risk are common

  • 41% of people with TB had diabetes, end stage renal disease, HIV infection, Hepatitis C, or another condition that can increase the risk of progression from latent to active TB disease.
  • The most common comorbidity was diabetes mellitus, occurring in 31% of cases.
  • 30% of persons with TB reported being current or former smokers.
  • HIV infection increases the risk for active TB disease, as well as for death with TB.
  • In 2023, 88% of patients with TB were tested for HIV. Of those tested, 81 (4.4%) were HIV-positive. The proportion of cases with HIV has fluctuated between 3.2% to 4.6% since 2014.
  • Among 46 people with HIV who also had a known CD4 count, 70% had a CD4 count under 200, indicating advanced HIV infection. 

TB affects children

  • TB in children is an indication of recent transmission particularly when it involves children under 5 years old. These young children are also vulnerable to the most severe forms of TB such as disseminated TB and TB of the central nervous system (CNS).

  • In 2023, there were 28 cases of TB among children under 5 years old. Of those, 7 (25%) had CNS TB.

Multidrug-resistant TB continues

  • Multidrug-resistant (MDR) TB is TB resistant to the two most potent first line drugs, isoniazid and rifampin. According to CDC, extensively drug-resistant (XDR) TB is MDR TB additionally resistant to fluoroquinolones and injectables, bedaquiline, or linezolid, the most potent second-line drugs.
  • In 2023, there were 24 (1.1%) MDR TB cases in California, an increase from 18 cases (1.0%) during 2022. During 2019-2023, three XDR cases were reported.
  • The proportion of TB cases in California that are MDR has remained constant (1–2%) since drug susceptibility data began being systematically collected in 1993.

TB can be prevented with LTBI treatment

Estimated LTBI cases,

  • More than 2 million Californians have LTBI. Only 23% are aware of their LTBI and only 13% have been treated.
  • The majority of people with LTBI (1.8 million) were born outside the U.S. 
  • An estimated 85% of TB cases occur because of progression from LTBI. This means treating LTBI will prevent many TB cases in California.

This document reflects provisional data as of February 02, 2024. ​                          ​Tuberculosis Control Branch Logo
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