Rate of reinfection tuberculosis after successful treatment is higher than rate of new tuberculosis.
BACKGROUND
In a high-tuberculosis (TB) incidence area of Cape Town, South Africa, there is a very high rate of unexplained recurrent TB. The incidence of new bacteriologically confirmed disease in the area is 313 per 100,000 individuals.


OBJECTIVE
To estimate the rate of recurrent TB attributable to reinfection after successful treatment.


METHODS
All patients with reported TB in the area between 1993 and 1998 were followed up to 2001 for disease needing retreatment (recurrences). Patients who were multi-drug-resistant or who had treatment failure, were transferred, or died during treatment were excluded. Analysis was restricted to patients for whom DNA fingerprinting of their Mycobacterium tuberculosis isolates was obtained. Reinfection TB was defined as a recurrent TB episode in which the strains of the separate episodes differed by more than four bands.


RESULTS
612 of 897 (68%) patients had a DNA fingerprint available at enrollment. Median duration of follow-up was 5.2 years. Recurrent TB occurred in 108 of 612 (18%) patients, of whom 61 of 447 (14%) experienced recurrence after successful treatment, and 47 of 165 (28%) experience recurrence after default. Of the 108 patients with recurrent TB, 68 (63%) had a DNA fingerprint in the second episode. Among these patients, 24 of 31 (77%) recurrences after successful treatment and 4 of 37 (11%) recurrences after default were attributable to reinfection. The reinfection disease rate after successful treatment was estimated at 2.2 per 100 person-years.


CONCLUSIONS
The age-adjusted incidence rate of TB attributable to reinfection after successful treatment was four times that of new TB. People who had TB once are at a strongly increased risk of developing TB when reinfected.
Verver
Suzanne
S
Desmond Tutu TB Center, Department of Pediatrics and Child Health, Stellenbosch University, Cape Town, South Africa. ververs@kncvtbc.nl
Warren
Robin M
RM
Beyers
Nulda
N
Richardson
Madalene
M
van der Spuy
Gian D
GD
Borgdorff
Martien W
MW
Enarson
Donald A
DA
Behr
Marcel A
MA
van Helden
Paul D
PD
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000995:Antitubercular Agents / Q000627:therapeutic use*; D002648:Child; D015331:Cohort Studies; D016001:Confidence Intervals; D003906:Developing Countries; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D016017:Odds Ratio; D011379:Prognosis; D012008:Recurrence; D012189:Retrospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D017678:Sex Distribution; D013019:South Africa / Q000453:epidemiology; D016019:Survival Analysis; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000188:drug therapy* / Q000453:epidemiology*; D014505:Urban Population
D000995:Antitubercular Agents