The tropical features of hepatitis C have not yet been fully elucidated due to the scarcity of data. However it has been estimated that two-thirds of the infected population lives in tropics. The most heavily affected regions are Africa, China, and southeast Asia with prevalence rates of 5.3, 3.0, and 2.4 p. 100 respectively. In several countries mostly in Africa, prevalence rates range from 5 to 10 p. 100 or higher. Age is a major risk factor for infection. The classic transmission modes, i.e., blood transfusion and intravenous drug use, do not account for these high prevalence rates. Another mechanism could be parenteral injection under unsafe conditions. The most widespread genotypes in tropical areas are genotypes 1, 2, and 3. Other genotypes can be encountered locally including genotype 4 in black Africa and Egypt, genotype 6 in southeast Asia, and genotypes 1 and 3 in India. The association of hepatitis C with chronic liver disease has been the focus of several studies, mainly in Africa. The seroprevalence of virus C ranges from 2 to 55 p. 100 in cases of chronic hepatitis or cirrhosis and from 0 to 47 p. 100 in cases of hepatocellular cancer. Hepatitis C could be the underlying cause of 33 to 50 p. 100 of chronic liver diseases not linked to virus B. It is observed more often in patients with chronic hepatitis or cirrhosis than cancer in which virus B is dominant. Infection by both virus is rare without liver disease but is more frequent in patients with cancer than chronic non-tumoral liver disease.
The genetic diversity of hepatitis E virus (HEV) has been extensively analysed during the last decade. Most sporadic and epidemic HEV strains are distributed into genotypes or groups. Nevertheless, few studies have looked at the polymorphism of HEV strains isolated from a given outbreak. A serum bank collected in Tanefdour, Algeria, during an acute hepatitis epidemic (1986-1987), retrospectively confirmed as hepatitis E, was analysed. Of the 69 serum samples collected within an 8-week period, 23 were positive for both partial ORF1 (replicase gene) and ORF2 (capsid gene) sequences. Inter- and intra-patient diversities were assessed by RFLP, and by sequencing a 448 bp sequence corresponding to ORF2. RFLP analysis distinguished three profiles: A (18/23), B (3/23) and C (2/23). Most isolates (18/23) shared 99.7-100 % sequence identity and the remainder showed 1-1.3 % divergence. HEV intra-patient diversity was studied using 12 isolates (seven displaying the major RFLP profile and five displaying minor RFLP profiles). For 9 of 12 isolates, additional intra-patient heterogeneity was revealed by RFLP analysis of 100 clones from each isolate and sequence diversity ranging from 0.11 to 3.4 %. These data strongly support the quasispecies organization of HEV during epidemics and could explain the adaptable behaviour of the virus in the host-pathogen interrelations.
Food borne disease outbreaks have increased in France, but outbreaks caused by Shigella are rare, accounting for only 73 cases (1.62%) in 1993. We report a food borne outbreak of Shigella flexneri strain 3 infection in a fire fighting unit in Paris between July 13th and 17th 1995. Forty of the 127 firemen suffered symptoms including acute diarrhea (80%), fever (50%) and blood and mucus in stools (1 case, 2.5%). Epidemiological investigation generated an unimodal epidemic curve suggesting a single source of contamination with no secondary cases. The median incubation period was between 43 hours 30 minutes and 51 hours 30 minutes. This is consistent with food borne Shigella infection. Statistical analysis of a case-control study implicated a mixed salad containing frozen shellfish from Asia (shrimps and mussels), served at lunch and dinner on July 13th 1995. Shigella was not detected in this salad by microbiological methods. However, inoculation with as little as 100 organisms can cause symptoms. There was low-level contamination with Escherichia coli (940 cfu/g) due to cross-contamination. Shigella flexneri strain 3 was isolated from 11 of 18 stool cultures, but was never isolated from cultures of stools provided by the cooks. All isolates had identical antibiotic resistance profiles. They were resistant to ampicillin and ticarcillin, moderately sensitive to amoxicillin-clavulanic acid, highly sensitive to aminosides, erythromycin and quinolones. This identical pattern in all isolates suggests a common source of contamination. Plasmid-based multiple resistance is common in this organism. Therefore, antibiotics should only be given to patients with evident clinical signs of infection. Treatment was symptom-based in all but 4 patients, who had acute diarrhea and were treated with ciprofloxacin. This antibiotic is well tolerated, has rapid bactericidal action and significantly reduces the duration of the symptoms and excretion of Shigella, thus preventing secondary contamination with this highly infectious bacterium. Thus, food borne outbreaks of Shigella can occur in countries with a high standard of living because of the increase in mass catering (e.g. fast food restaurants) and importation of foodstuffs from developing countries with endemic shigellosis. This is a public health problem because of the morbidity and absenteeism due to illness, particularly when the patients are firemen responsible for emergency management.
