| Typhoid fever was an old disease, which existed about 15 000 to 150 000 years ago. Typhoid fever and paratyphoid fever were both acute febrile illnesses caused by Salmonella typhi or Salmonella paratyphi A,B,C. In China,these diseases belonged to class B of notifiable communicable diseases. It was a serious public health problem which the global had to face.In this investigation,we utilized case-control study and pulsed-field gel electrophoresis (PFGE) laboratory testing to analyze the possible reasons and risk factors for this outbreak in Yuanjiang country, providing a reference to track the possible resource of infection and give a basis to control and prevent these diseases.Through investigation, cases were mainly found in the county of Lijiang town.All people were susceptible while cases are mainly young and middle-aged people who were mostly farmers between 30 to 40 years old. The possible reasons were the poor sanitation, low rate of qualified cutlery disqualified drinking water and vegetables polluted by sewage.Results from Case-control study showed that the main risk factors were dining out(OR=2.312,95%CI: 1.072-4.988) and eating raw vegetables (OR=1.704,95%CI:0.000-7.441). Dinning out would increase danger of infection of typhoid and paratyphoid. Frequency of dinning out and risk of infection had dose response relationships. More times of dinning out, more risk of infection. (the frequency?6/week,OR=26.736, 95%CI : 7.417-96.374, 3-5/week : OR=12.250,95%CI: 5.468-27.444; 1-2/week: OR=2.888,95%CI: 1.318-6.327);Eating raw vegetable was one of risk factors, no matter eating in restaurants(OR=11.201,95%CI: 5.653-22.192) or at home.(OR=3.649,5%CI: 1.535-8.672).Going out, drinking unboiled water and having guests were not significant.Single factor regression analysis found that the consumption of coriander(OR=1.399,95%CI: 0.760-2.576), Houttuynia(OR=1.033,95%CI:0.499-2.140) and other cold dishes (OR=1.347 95%CI: 0.635-2.859, cooked salad to eat) were statistically significant.Study showed the case group and the control group both bought raw vegetables mainly from the vegetable market, restaurant and Food stalls. The results were statistically significant through the ?2 test(Food stalls x2=8.00, P=0.005; Restaurants?2=3.749, P=0.000; Marketsx2=23.378, P=0.000).The 160 paratyphi A strains which isolated from Yuanjiang (Four strains from sewage separation) were tested with PFGE. Also 292 paratyphi A strains which isolated from Hongta district were tested with the same method. Thirty-five different phage types were found from the strains isolated from Hongta district. The phrage types of JKPX01.CN0001/ JKPS18.CN0002 were superior types. The phage types of KPX01.CN0001/JKPS18.CN0001 were sub-superior types. Seven different phage types were detected from the 160 strains from Yuanjinag country. The superior type was JKPX01.CN0001/JKPS18.CN0001 which was similar with the sub-superior types which were tested from the Hongta strains. Based on the epidemiological investigation, the results indicated that the dissemination of cases in Yuxi area might be responsible for the outbreak of paratyphoid in Yuanjiang country. |
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