Molecular epidemiology of tuberculosis in a low- to moderate-incidence state: are contact investigations enough?
To assess the circumstances of recent transmission of tuberculosis (TB) (progression to active disease <2 years after infection), we obtained DNA fingerprints for 1172 (99%) of 1179 Mycobacterium tuberculosis isolates collected from Maryland TB patients from 1996 to 2000. We also reviewed medical records and interviewed patients with genetically matching M. tuberculosis strains to identify epidemiologic links (cluster investigation). Traditional settings for transmission were defined as households or close relatives and friends; all other settings were considered nontraditional. Of 436 clustered patients, 115 had recently acquired TB. Cluster investigations were significantly more likely than contact investigations to identify patients who recently acquired TB in nontraditional settings (33/42 vs. 23/72, respectively; p<0.001). Transmission from a foreign-born person to a U.S.-born person was rare and occurred mainly in public settings. The time from symptom onset to diagnosis was twice as long for transmitters as for nontransmitters (16.8 vs. 8.5 weeks, respectively; p<0.01). Molecular epidemiologic studies showed that reducing diagnostic delays can prevent TB transmission in nontraditional settings, which elude contact investigations.
Cronin
Wendy A
WA
Maryland Department of Health and Mental Hygiene, Baltimore, Maryland 21201, USA. croninw@dhmh.state.md.us
Golub
Jonathan E
JE
Lathan
Monica J
MJ
Mukasa
Leonard N
LN
Hooper
Nancy
N
Razeq
Jafar H
JH
Baruch
Nancy G
NG
Mulcahy
Donna
D
Benjamin
William H
WH
Magder
Laurence S
LS
Strickland
G Thomas
GT
Bishai
William R
WR
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D016358:Contact Tracing / Q000379:methods*; D016172:DNA Fingerprinting; D005260:Female; D005838:Genotype; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D008396:Maryland / Q000453:epidemiology; D008875:Middle Aged; D017720:Molecular Epidemiology; D009169:Mycobacterium tuberculosis / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D012150:Polymorphism, Restriction Fragment Length; D012307:Risk Factors; D012959:Socioeconomic Factors; D013997:Time Factors; D014376:Tuberculosis / Q000175:diagnosis / Q000453:epidemiology* / Q000382:microbiology* / Q000635:transmission