Multidrug-Resistant Tuberculosis Outbreak among US-bound Hmong Refugees, Thailand, 2005

In January 2005, tuberculosis (TB), including multidrug-resistant TB (MDR TB), was reported among Hmong refugees who were living in or had recently immigrated to the United States from a camp in Thailand.We investigated TB and drug resistance, enhanced TB screenings, and expanded treatment capacity in the camp.In February 2005, 272 patients with TB (24 MDR TB) remained in the camp.Among 17 MDR TB patients interviewed, 13 were found to be linked socially.Of 23 MDR TB isolates genotyped, 20 were similar according to 3 molecular typing methods.Before enhanced screening was implemented, 46 TB cases (6 MDR TB) were diagnosed in the United States among 9,455 resettled refugees.After enhanced screening had begun, only 4 TB cases (1 MDR TB), were found among 5,705 resettled refugees.An MDR TB outbreak among US-bound refugees led to importation of disease; enhanced pre-immigration TB screening and treatment decreased subsequent importation.G lobally, 9 million new cases of tuberculosis (TB) were reported in 2004 (1), ≈4.3% of which were multidrugresistant TB (MDR TB) (2).MDR TB, defi ned as infection with Mycobacterium tuberculosis resistant to at least isoniazid and rifampin, complicates TB control efforts because it requires prolonged treatment with drugs that are less po-tent, more costly, and more toxic than traditional isoniazidand rifampin-based regimens (3,4).These factors challenge implementation of effective TB control programs, particularly in developing countries.Currently, 56% of TB cases in the United States occur in foreign-born persons (5), and rates are highest among recently arrived immigrants (6,7).Refugee populations are particularly vulnerable to TB and drug-resistant TB (8-12).Annually, 50,000-70,000 refugees immigrate to the United States (13); before entry, they must undergo standard preimmigration screening for TB.Despite screening, however, refugee populations have exhibited high TB incidence rates shortly after arrival in the United States (14-16).One contributor to high postarrival TB rates is the low sensitivity of the current pre-immigration TB screening algorithm, which has been estimated to identify <35% of all TB cases (17).In December 2003, the US Department of State announced a refugee resettlement program for ≈16,000 Hmong refugees from Laos, who had been living in a temporary camp for displaced persons in Lopburi, Thailand, for >10 years.The fi rst refugees arrived in the United States in June 2004; by January 2005, ≈10,000 had immigrated to the United States.Initial reports, after health assessments of newly arrived refugees, identifi ed 37 TB cases, 4 of which were MDR TB (18).Simultaneously, cases of MDR TB were confi rmed in Thailand in refugees awaiting resettlement.Immigration to the United States was temporarily halted in January 2005, while the US Centers for Disease Control and Prevention (CDC) and international partners investigated the factors that led to emergence and dissemination of TB, including MDR TB, among these refugees.Results from the investigation guided implementation of enhanced TB screening and treatment for the ≈6,000 refugees remaining in the camp in Thailand.