Outbreak of hepatitis A infection among intravenous drug users in Suffolk and suspected risk factors.

A prolonged outbreak of hepatitis A infection amongst drug users in Suffolk prompted a study of the natural immunity against hepatitis A in this population, and a retrospective analysis of the relationship between specific drug-taking behaviours and the risk of hepatitis A infection. Prior to the outbreak, age-specific seroprevalence of hepatitis A IgG in drug users was similar to that amongst blood donors in the region. Of those without effective immunity, intravenous drug users, multiple drug users and those injecting frequently were more likely to have developed hepatitis. The reported frequency of equipment sharing and the number of injecting partners were not related to the risk of infection. The potential for blood-to-blood, and a suggested faecal-blood transmission were considered to be important in propagating the outbreak in this population. We suggest that a single dose of hepatitis A vaccine administered opportunistically should be used in outbreaks involving drug users.

Farming Systems and Political Growth in Ancient Oaxaca: Physiographic features and water-control techniques contributed to the rise of Zapotec Indian civilization.

The Valley of Oaxaca's large flat floor, high water table, low erosion rate, and frost-free floodplain give it a higher agricultural potential than that of most surrounding areas. The development of the pot-irrigation system early in the Formative period gave it a head start over other valleys, where the low water table did not permit such farming; Oaxaca maintained its advantage by assimilating canal irrigation, barbecho, infield-outfield systems, flood-water farming, and hillside terracing as these methods arose. With the expansion of population in the high-water-table zone of the high alluvium, competition for highly productive land and manipulation of surpluses may have led to initial disparities in wealth and status; competition probably increased when canal-irrigation systems were added during the Middle Formative, improving some localities to the point where one residental group owned land more valuable than that of its neighbors.