Enteric fever remains a major public health challenge. Economic development and progress towards the achievement of MDG 7 will assist low- and middle-income countries experience similar reductions in enteric fever as were seen in industrialized countries a century ago. The occurrence of enteric fever in poor populations with limited access to diagnostic services means that disease burden is poorly quantified and policy makers have lacked the data needed to make decisions about the deployment of enteric fever prevention measures and vaccines. However, recent studies and vaccine demonstration projects are beginning to change this situation in Asia. Such data are not yet available for other regions, particularly sub-Saharan Africa. While Ty21a and Vi polysaccharide vaccines are effective, the development of cheap, safe vaccines with efficacy among infants that can provide protective immunity after a single dose and that could be easily adapted for EPI would facilitate adoption into national programs. The growing importance of S. Paratyphi A as a cause of enteric fever is of great concern, particularly due to the lack of availability of an effective vaccine.
Antimicrobial resistance continues to emerge in S. Typhi and S. Paratyphi resulting in loss over time of the value of traditional first-line drugs and fluoroquinolones. DCS and more recently fluoroquinolone resistance have led to greater use of third generation cephalosporins. Azithromycin and the newer fluoroquinolone gatifloxacin show some promise for the management of uncomplicated typhoid fever and provide a useful alternative to ceftriaxone for settings where a cheaper oral regimen is needed. The historical adaptation of Salmonella to patterns of antimicrobial use suggests that vigilance for the emergence of ceftriaxone-resistant strains in warranted.
Recent insights into the evolution of S. Typhi and S. Paratyphi A from genomics confirm that the organisms are genetically monomorphic and show other features of highly host-adapted pathogens. These features remind us of the organisms’ vulnerabilities and the potential for major gains in disease control. Added to the increasing complexity of managing enteric fever due to antimicrobial resistance, there is a strong case for much greater effort in disease control through improvements in sanitation, greater access to safe water and food, identification and treatment of S. Typhi carriers, and the more widespread use of currently available vaccines in high-risk populations.