Refugee cases show TB respects no borders

Screening measures heightened after debacle

The importation of tuberculosis into the United States via a group of screened refugees underscores how difficult it is to eliminate tuberculosis in the United States when some 2 billion people are infected globally.

The U.S. Department of State opened a resettlement program for 15,707 Hmong refugees who had been displaced from Laos and were living on the grounds of Wat Tham Krabok, a Buddhist temple in Thailand.

During June 2004-January 2005, the United States resettled 9,459 Hmong refugees in 20 states. As the newly arrived refugees underwent health assessments at local health departments and in private health care facilities, 37 TB cases, including four multidrug-resistant (MDR) cases, were reported.1 This finding coincided with assessments in Thailand, where 17 (33%) of 52 culture-confirmed cases among refugees were determined to be MDR. In contrast, among all new TB cases reported in the United States during 2004 with drug-susceptibility results, 1% were MDR-TB, according to the Centers for Disease Control and Prevention (CDC).

"All of a sudden, we started seeing these individuals who were purportedly screened [diagnosed with TB]," said Rachel Stricof, MT, MPH, an epidemiologist at the bureau of TB control at New York State Department of Health and a liaison member of the CDC’s Healthcare Infection Control Practices Advisory Committee (HICPAC). "We also found out that about 10% of them had MDR-TB. They are entering communities — going in and living with other people in their society, often in crowded living conditions."

Compared to miniscule TB incidence in the United States, the rate of TB found in the original camp was striking, she emphasized recently in Baltimore at the annual meeting of the Association for Professionals in Infection Control and Epidemiology. "Our rate of TB is less than 5 per 100,000," she said. "The rate in this camp is in excess of 1,700 per 100,000."

Most of the refugees went to California, Minnesota, and Wisconsin. "Those are not high prevalence areas for TB, so people were not always suspecting [cases]," Stricof noted. "Now there are over 400 contact investigations going on in the United States surrounding these individuals. We frankly don’t know who has been exposed to an MDR-TB case vs. a susceptible strain."

Long-term follow-up will be expensive

After enhanced screening in Thailand and intensified TB-control measures in the United States, the resettlement effort resumed Feb. 16, 2005. A majority of the Hmong refugees in Thailand and the United States with TB diagnosed were started on treatment and monitored.

As of July 15, 2005, no additional TB cases had been diagnosed among newly resettled Hmong refugees, but health departments should continue to ensure careful monitoring for TB among this refugee group, the CDC advises.

Approximately 50,000-70,000 refugees resettle in the United States each year. Before resettlement, all refugees undergo medical screening to prevent importation of diseases that pose an immediate public health risk.

The standard TB-screening algorithm, used in early 2004 to evaluate Hmong refugees in Thailand, includes a medical history and physical examination for all applicants and a chest radiograph for people at least 15 years old. Applicants with clinical or radiologic findings suggestive of TB disease submit three sputum specimens for acid-fast bacilli (AFB) smear microscopy. Those with positive results must begin anti-TB treatment and have follow-up specimens with consistently smear-negative results before travel to the United States is allowed. The standard pre-migration algorithm was revised in May 2004 to add requirements for mycobacterial culture and drug-susceptibility testing.

California, where approximately one-third of the refugees were resettled, reported 24 (65%) of the 37 TB cases, including 10 among children younger than 15. Those cases, as directed by the initial screening algorithm, had not received a pre-migration TB screening. Moreover, the situation will require ongoing and expensive follow-up among all of the refugees, because all were at risk for exposure and they may develop latent TB infection (LTBI). Per person, the estimated costs of detecting disease and treating patients with LTBI range from $208 to $11,125, and the direct medical costs associated with TB and MDR-TB disease range from $3,800 to $137,000, depending on case complexity, the CDC reports.

The projections likely underestimate the costs for treating Hmong refugees because they exclude the additional expenses of providing culturally appropriate outreach, interpretation, and transportation services.

The annual number of immigrants to the United States continues to increase, and TB is the medical condition most frequently diagnosed among applicants for permanent residence, according to the CDC.


  1. Centers for Disease Control and Prevention. Multi-drug-resistant tuberculosis in Hmong refugees resettling from Thailand into the United States, 2004-2005. MMWR 2005; 54(30);741-744.