In 2005, King County reported 127 cases of active tuberculosis (TB) disease. This represents a 5 percent decrease from the 2004 count and marks a continued decline since 2002 when 158 TB cases, a 30-year historic high, were reported. Between 2002 and 2005, several new TB control efforts were initiated:

In King County, TB continues to disproportionately affect the foreign-born, who represented 95 cases reported in 2005. King County’s TB rate (7.0 per 100,000 population) remains higher than the national rate (4.8 per 100,000).

Age, Race, Ethnicity and Nativity

TB case rates vary by factors such as age, race, ethnicity and country of origin. The largest decline in case rates among age groups occurred among 15-24 year-olds, where rates declined from 12.2/100,000 in 2004 to 7.0/100,000 in 2005. The TB case count among children 0-14 years was four. Blacks (37.0/100,000) and Asians (24.5/100,000) had disproportionately higher rates of TB. In 2005, 75 percent of reported cases occurred among foreign-born persons, similar to the 2004 proportion. The highest case numbers came from Vietnam, Ethiopia, the Philippines, Somalia and Mexico.

TB-HIV Co-infection

HIV is a significant risk factor for TB. There were seven TB cases among HIV infected persons in King County, representing 5.5 percent of all TB cases reported in 2005. This represents an increase from 2004, but is consistent with proportions from previous years (years 2001–2003). The proportion of cases offered HIV testing in King County has improved from 85 percent to 99 percent over the past five years.

Drug Resistant TB

In 2005, 15 percent of TB cases were resistant to at least one TB medication in King County. Ten percent of all TB cases exhibited primary resistance to isoniazid (INH) in 2005. Multi-drug resistant TB (MDR-TB: TB resistant to at least isoniazid and rifampin, the most effective TB medications) is exceedingly costly and difficult to treat. In 2005, two cases (2 percent of cases) of MDR-TB were reported.

TB Treatment

The proportion of TB patients initially placed on a standard four-drug regimen continues to remain above 90 percent. The proportion of patients who were treated with directly observed therapy has increased from 61 percent in 2001 to 99 percent in 2004, the latest year with available outcome data.

Summary

The program continues to face many ongoing challenges, such as (1) the high proportion of TB patients who live in poverty and who have special needs in respect to and acculturation, and (2) the transient and migratory nature of many individuals at high risk for TB.

Because of a large pool of individuals with latent TB infection (estimated 100,000 people in King County, and a third of the world’s population), lack of convenient preventive medications, and lack of an effective TB vaccine, it is unlikely that TB will be eliminated anytime soon. To manage this disease with the tools currently available, the TB Control Program focuses on (1) case management of patients with active TB disease in order to ensure the cure of all TB cases, stop further transmission of TB and prevent development of multi-drug resistant TB; (2) timely and thorough contact investigations around active TB cases to identify, evaluate and treat those who were exposed and recently infected and (3) efforts to enhance targeted TB testing and treatment of latent TB infection.

Next Month

Next month the EPI-LOG will focus on the important role that King County health care providers play in the control of TB in our community. In the meantime, please continue to consider tuberculosis in the evaluation of persons with persistent cough, fever, weight loss, and other persistent undiagnosed symptoms, and call the TB Control Program at (206) 744-3954 to report any newly suspected cases.