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By Gary Evans, Senior Staff Writer
After two decades of steady, incremental decline, tuberculosis in the United States has leveled off at some 3 cases per 100,000 people – a rate that will not result in the goal of TB elimination (less than 1 case per million), the Centers for Disease Control and Prevention reports.
“Epidemiologic modeling suggests that even if the previously observed annual declines in the United States had been sustained, TB elimination …would not occur by the end of this century,” the CDC stated. “The determinants of this leveling in TB incidence are not yet clear; further evaluation of available data is required to understand the causes of this trend.”
The 1985–1992 resurgence of TB in the U.S. was attributed to HIV coinfection, immigration from countries with higher prevalence and increased transmission. However, the proportion of TB patients coinfected with HIV has declined substantially in the United States, and TB incidence among U.S. foreign-born persons -- while still high -has continued to decline. In contrast, the stabilization of TB incidence among U.S.-born persons, together with evidence provided by molecular genotyping of TB cases, demonstrates that TB transmission within the United States continues to occur, the CDC noted in data released in conjunction with World TB Day March 24th.
“The continued occurrence of TB cases among U.S.-born children is further corroboration, because TB disease in a young child is a sentinel event representing recent infection,” the CDC warned. “Substance abuse, incarceration, and homelessness associated with TB outbreaks highlight some of the complicated case management work required on the health department frontlines of TB control.”
CDC key points on TB in the U.S. include:
• Effective TB control requires diagnosing cases as early as possible during the illness, thus allowing earlier airborne precautions and curative treatment to interrupt transmission. An early diagnosis for a patient with infectious TB also permits a timely contact investigation, which is essential to detect and prevent additional TB cases. Recently infected contacts, particularly children, benefit greatly from treatment to avert progression to active TB disease.
• Since 2003, TB incidence among Native Hawaiians/other Pacific Islanders and American Indians/Alaska Natives has remained high despite declining incidence among Hispanics and non-Hispanic Asians, whites, and blacks.
• Two thirds of all U.S. TB cases occur among foreign-born persons, often years after arrival, which is consistent with disease progression following years of untreated latent TB infection. Epidemiologic modeling indicates that eliminating the threat of TB in the United States will require additional strategies to reduce TB in the countries of origin and expand treatment of latent TB infection among the foreign-born persons.