Human Suis and Pig Diseases in Northern Vietnam

• Temporal proximity to the nearest pig outbreak of human cases versus human controls [ Time Frame: Up to 1 year ] [ Designated as safety issue: No ]
  The number of days seperating identified nearest pig outbreak and identified human cases of S. suis versus the number of days seperating identified nearest pig outbreak and human controls.
  
  
• Spatial proximity to the nearest pig outbreak of human cases versus human controls [ Time Frame: Up to 1 year ] [ Designated as safety issue: No ]
  The number of kilometers seperating the identified nearest pig outbreak and identified human cases of S. suis versus the number of kilometers seperating the identified nearest pig outbreak and human controls.
  
  

• Number of human S. suis cases [ Time Frame: One year ] [ Designated as safety issue: No ]
  Total number of human S.suis cases recorded at NHTD in 2010.
  
  
• Number of pig disease outbreaks [ Time Frame: One year ] [ Designated as safety issue: No ]
  Total number of pig outbreaks identified within 2010 in the Northern region.
  
  

Streptococcus suis is a zoonotic agent which can cause severe systemic infection in humans exposed to infected pigs or pig derived products. Over 700 cases have been reported worldwide, most of them were in China and Vietnam in the last few years.

In Vietnam, S. suis infection in adults is common, and patients with S.suis are often admitted to the National Hospital for Tropical Diseases (NHTD), a tertiary referral hospital for infectious diseases in northern Vietnam. In 2007, 50 laboratory confirmed cases with S.suis were reported at this hospital, and in 2010, 65 laboratory confirmed S.suis cases have been identified by September. Pig breeding and pork consumption is popular in Vietnam, with the majority of pigs and meat supply channelled from small-scaled un-controlled farmers and slaughterhouses, which pose a great potential health risk to people involved in the chain. A case-control study conducted in southern Vietnam showed that occupational exposure, raising pigs at home and consuming high-risk dishes from pigs significantly increased the risk of S. suis infection.

It has been suggested that the incidence of human S. suis cases is possibly linked to the occurrence of Porcine Respiratory and Reproductive System (PRRS) virus outbreaks in northern Vietnam. In 2010, the disease has spread to over 30 provinces over the country, with many outbreaks reported in northern provinces in the period from April to July. Field observations in other countries showed that PRRS virus infection increased pig's susceptibility to S. suis infection, including serotype 2 and 7. Therefore, PRRS virus outbreaks might have increased the risk of S. suis transmission to humans through exposure to pigs with PRRS virus infection and concomitant S. suis disease. Nevertheless, sufficient data are not available to confirm or refute this hypothesis. Knowledge of spatial and temporal relationships between human S.suis infections and disease outbreaks in pigs can increase our understanding of risk factors for human S.suis infection and support disease prevention and preparedness in the community.