[Epidemiological and etiological characteristics of typhoid and paratyphoid fever in Ningbo during 1988 - 2007].
OBJECTIVE
To study the epidemiological and etiological characteristics of typhoid and paratyphoid fever in high epidemic areas.


METHODS
Reported data on typhoid and paratyphoid fever during 1988-2007 in Ningbo were analyzed epidemiologically. Shellfish from the market was collected for laboratory testing and Salmonella typhi strains collected from the patients were also studied.


RESULTS
Number of reported cases on both typhoid and paratyphoid fever was 19 404 with 7 deaths, from 1988 to 2007. The annual mean incidence was 17.68 per one hundred thousand with the fatality rate as 0.36 per thousand. Most cases were among adults aged 20-50 years and an obvious regional distribution was observed with high incidence seen in winter and spring. Since 1990s, the advantage strain had changed from Salmonella typhi to Salmonella paratyphi A. Etiologic studies showed that raw Anadara subcrenata and oyster were the main risk factors. One Salmonella paratyphi A strain was detected in both Anadara subcrenata and oysters collected from the market, which contained TEM-1 drug resistance gene. PFGE genotyping showed that PFGE-X2 was the strain which causing pandemic in Ningbo.


CONCLUSIONS
Eating contaminated raw shellfish like oysters and hairy clams was the primary risk factor, responsible for the outbreaks. Salmonella paratyphi A was the advantages pandemic strain in Ningbo. Strategies as supervision on personal hygiene and health education should be strengthened.
Xu
Guo-Zhang
GZ
Ningbo Municipal Center for Disease Control and Prevention, Ningbo 315010, China.
Xu
Jing-Ye
JY
Zhou
Ai-Ming
AM
Jin
Chun-Guang
CG
Mao
Guo-Hua
GH
Shi
You-Zhang
YZ
Dong
Hong-Jun
HJ
Yang
Yuan-Bin
YB
D000328:Adult; D000818:Animals; D002681:China / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D010284:Paratyphoid Fever / Q000453:epidemiology / Q000209:etiology / Q000382:microbiology*; D012307:Risk Factors; D012482:Salmonella paratyphi A / Q000302:isolation & purification*; D012485:Salmonella typhi / Q000302:isolation & purification*; D012621:Seasons; D012758:Shellfish / Q000382:microbiology*; D014435:Typhoid Fever / Q000453:epidemiology / Q000209:etiology / Q000382:microbiology*; D055815:Young Adult