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TB Notes 2, 2004
Highlights from State and Local Programs
A Multi-Jurisdictional TB Outbreak Among Seasonal
Agricultural Workers From Oaxaca, Mexico
Year round, California employs more than 900,000 migrant and seasonal
agricultural workers, 90% of whom are Mexico-born.1,2
In the past two decades there has been a rapid increase in the number
of indigenous migrant workers in California: in 2003, approximately
50,000 to 100,000 agricultural workers were of Mixtec descent, originating
from the Mexican states of Oaxaca, Puebla, and Guerrero. Mixtecs
are Mexicans of indigenous (American Indian) descent. The group
consists of many different communities with their own cultures and
dialects of the Mixtec language. Catastrophic soil erosion and resultant
crop failures in these areas have forced Mixtecs and other indigenous
groups to migrate through Baja California and the western United
States in order to find work.
Challenges for migrant populations in general are magnified in
indigenous groups: they face discrimination from other migrant groups
and employers, they receive the lowest wages for the least desirable
jobs, and many, particularly the women, speak only their native
language and cannot communicate effectively in Spanish or English
with employers or health care providers.3
In June 2003, a local health jurisdiction (LHJ) requested assistance
from the California TB Control Branch (TBCB) Outbreak Response Team
(ORT) to contain an outbreak of TB among Mixtec seasonal agricultural
workers. The LHJ had found five persons with TB (3 adults and 2
children) in several related households. The group came from one
small village in Oaxaca and traveled frequently among six LHJs in
California and one in Washington state. The index case was a young
Mixtec male who had a self-reported history of TB treatment in 2002
in Oaxaca. In March 2003, he arrived in California and was subsequently
diagnosed with smear- and culture-positive pulmonary TB in May.
Despite exhaustive efforts to promote adherence, including detention
in a health facility, the index case was lost to follow-up in June
2003. A newly identified secondary case was also lost to follow-up
at that time, before being informed of her TB diagnosis. Additionally,
a tuberculin skin test (TST)-positive, symptomatic 18-month-old
was lost to follow-up before initial evaluation could be completed.
The LHJ requested ORT assistance to locate lost cases and suspects,
and to identify additional contacts for evaluation.
Challenges to outbreak containment included frequent client movement
between Mexico, California, and Washington; sociocultural, economic,
language, and transportation barriers to accessing health care;
and difficulty in establishing trust between health departments
and clients. Contacts were difficult to elicit, locate, evaluate,
and treat, primarily owing to clients’ fear of health authorities
because of their undocumented status. To contain the outbreak, the
Outbreak Response Team (ORT) facilitated a coordinated approach
with the participation of all involved entities, including state
TB control programs in California and Washington, affected LHJs,
community- based organizations (CBOs), CureTB, and TBNet.
To assess the extent of the outbreak, LHJs surrounding the outbreak
county and those with known concentrations of migrant workers were
canvassed for Oaxaca-born TB cases diagnosed in 2003. A TB outbreak
alert was distributed to all Health Officers in California and community
health care providers within affected LHJs, requesting rapid reporting
of anyone from Oaxaca newly diagnosed with TB. Isolates from persons
from Oaxaca with culture-confirmed TB with known or suspected epi-links
were genotyped by CDC. The TBCB ORT, State of Washington TB Control,
and LHJs held regular meetings and teleconferences to set outbreak
investigation priorities and exchange information. A centralized
outbreak database was maintained by the TBCB ORT and used to track
patient movement and evaluation status.
In cooperation with the Fresno Health Department Communicable
Disease Outreach Program, the Binational Center for Indigenous Oaxacan
Development (CBDIO) in Fresno, California, provided TB education
and outreach to Mixtec audiences. This was accomplished through
radio and TV broadcasts in Spanish and Mixtec and a TB patient
education audiotape that was recorded and distributed to health
departments. Mixtec interpreters were located through CBOs, including
the CBDIO and California Rural Legal Assistance. Oaxacan community
leaders were enlisted and the TBCB provided additional funds to
the primary outbreak LHJ to hire a Oaxacan consultant to enhance
LHJ cultural and language competence. LHJs and the TBCB ORT worked
with TBNet to improve continuity of care as patients moved
between US locations by enrolling them in the TBNet program.
It was also necessary to coordinate TB care in Oaxaca for persons
with TB disease returning home before completion of treatment. Access
to health care in the home village is limited, with the nearest
clinic four hours away by bus. CureTB coordinated closely with health
care staff in the home village area, who in turn coordinated with
village leaders to ensure continuing therapy for persons with TB
As of December 2003, 68 individuals were identified through this
outbreak investigation and 56 completed evaluation. Ten (18%) have
TB disease (5 culture-confirmed adults with pansusceptible disease,
5 clinically diagnosed pediatric cases), two (4%) are TB suspects,
and 34 (61%) have latent TB infection. Eight of 10 outbreak cases
and one TB suspect moved one or more times during evaluation and
treatment. The index case was found in his home village in Mexico
and was restarted on treatment; however, after only about 2 months
of therapy it was reported that he had left his village and was
returning to California. Efforts are currently underway to locate
him. Thanks to information obtained through our active surveillance
efforts, the lost secondary case was located in Washington state
and started on therapy in August 2003. She returned to California
in September and subsequently went back to Mexico in October, where
her treatment continued as a result of close coordination between
CureTB and health care providers in Mexico. In January 2004, she
returned to California where therapy continues. The 18-month-old
was located and evaluated in August 2003 and remains on treatment
for clinically diagnosed TB. All other cases remain on treatment.
Genotyping results on isolates from the five culture-confirmed
adult outbreak cases show an identical DNA fingerprint among four
of the isolates, suggesting transmission between these individuals
or from a common source, or a TB strain endemic to the home village.
Additionally, an isolate from a 2001 pleural case diagnosed in Washington
state who came from the same village has a matching RFLP pattern
with this outbreak strain.
This outbreak revealed a very high proportion of tuberculin skin
test-positive individuals (80% of those evaluated). Interruptions
in treatment, delays in diagnosis, and crowded living conditions
contributed to extensive transmission in this outbreak. Breaks and
delays in treatment were related to fear of authorities, lack of
financial resources, lack of transportation, long work hours, language
barriers, lack of TB knowledge, and frequent movement. Results from
this investigation highlight the difficulties in containing TB outbreaks
in migrant workers and indicate the importance of collaboration
between community partners and health jurisdictions at local, state,
and national levels for containment of an outbreak among a highly
mobile population. Involving community leaders, providing adequate
interpretation, and using all available media to communicate key
messages are effective methods for creating awareness and establishing
trust within a hard-to-reach population, and thus decreasing lost
cases and suspects and halting transmission.
The genotyping results and anecdotal information obtained from
case interviews suggest that in addition to U.S.-based transmission,
there may be ongoing TB transmission in the home village. Continued
coordination with health authorities in Mexico will be critical
to ensuring containment of the outbreak on both sides of the border.
—Submitted by Tina Albrecht, MSPH, Public Health
and D’Arcy Richardson, RN, PHN, MS, CNS,
TB Outbreak Response Officer/Nurse Epidemiologist
California State TB Control Branch
1. Migrant and Seasonal Farmworker Enumeration Profiles Study –
California. September 2000.
2. California Institute for Rural Studies, Rural California Report.
Who Does California Farmwork. Fall 2001; vol 12 (3).
3. Zabin C, Kearney M, Garcia A, Runsten D, and Nagengast C. Mixtec
migrants in California agriculture: a new cycle of poverty. Davis,
CA: California Institute for Rural Studies; 1993.