Molecular epidemiological investigation of a typhoid fever outbreak in South Africa, 2005: the relationship to a previous epidemic in 1993

Abstract

In 2005, over 600 clinically diagnosed typhoid fever cases occurred in South Africa, where an outbreak had been previously described in 1993. Case-control and molecular investigations, including Salmonella enterica serovar Typhi (S. Typhi) isolates from that area from 1993, 2005 and later, were undertaken. Controls were significantly older than cases (P=0·003), possibly due to immunity from previous infection, and a significantly larger proportion had attended a gathering (P=0·035). Exposure to commercial food outlets and person-to-person transmission was not significant. Pulsed-field gel electrophoresis and multi-locus tandem repeat analysis revealed common clusters of S. Typhi strains identified in 1993 and 2005 as well as in 2007 and 2009. This outbreak probably occurred in a non-immune population due to faecally contaminated water. S. Typhi strains appeared to be related to strains from 1993; failure to address unsafe water may lead to further outbreaks in the area if the current population immunity wanes or is lost.

Typhoid Fever in South Africa in an Endemic HIV Setting

“…Incidence rates of culture-confirmed typhoid fever were between 0.11 and 0.39 per 100,000 population; peaking in 2005 and 2006, due to typhoid outbreaks of over 600 clinically diagnosed cases, of which approximately 160 were culture-confirmed and captured in our surveillance [19]. …”

“…Primarily, missing data for certain clinical parameters may have affected the data analyses and results. Secondly, not all cases of typhoid fever over the study period were included: the majority of cases related to the 2005 typhoid fever outbreak did not have blood cultures done due to resource constraints [19]. In non-outbreak years, cases may similarly have been missed, thus burden of disease estimates could not be calculated.…”

Salmonella chronic carriage: epidemiology, diagnosis, and gallbladder persistence

“…In such models, however, the role of carrier-transmitted infections becomes progressively more important as the overall incidence of disease decreases, becoming critical for the maintenance of a stable, endemic infection within the community. This scenario is supported by population data from regions where implementation of effective public health interventions to prevent and treat typhoid have resulted in dramatic reduction- but not elimination- of the disease [43]. Furthermore, in these regions, chronic asymptomatic carriers play an important role in continued disease transmission, with the majority of outbreaks being foodborne and associated with asymptomatic chronic carriers employed as food preparers or handlers [44].…”

International collaboration tracks typhoid fever cases over two continents from South Africa to Australia

“…In recent years, the number of typhoid fever cases notified in SA has decreased. However, outbreaks of typhoid fever do occasionally still occur in the country: a recent outbreak of typhoid fever occurred in 2005 in the town of Delmas (Keddy et al, 2011). In the present study, we report on the epidemiological investigation of a cluster of typhoid fever cases in Pretoria, SA, in 2010 and further report on how this outbreak strain was tracked from SA to Australia.…”