Typhoid fever from water desalinized using reverse osmosis.

In May 1992, 81 bacteriologically confirmed cases of typhoid fever (TF) were identified in all districts of Tabuk City in northwestern Saudi Arabia. Attack rates (AR) in residential districts ranged from 0.9-10.3 per 10,000. Confirmed cases included 9 workers in the city's referral hospital, King Khalid Hospital (AR 140/10,000), 2 in families of medical staff, 57 in the community (AR 4.4/10,000) and 13 in a local military cantonment (AR 0.8/10,000). The outbreak began with the onset of TF in the three areas within 5 days, continued for 7 weeks, and ended 2 weeks after chlorination began. Among water sources, the odds ratio (OR) was highest (2.6; 95% confidence interval [CI] 1.25-5.39) for water purchased from reverse osmosis (RO) plants, especially RO plants supplied by one well (ASUW) (OR = 7.05; 95% CI 2.51-20.7). The aquifer for ASUW lay partially beneath a depression where city sewage collected. Unchlorinated water samples from ASUW 1 month after the outbreak ended yielded coliforms. ASUW probably became contaminated with Salmonella typhi when KKH demand overtaxed the aquifer and drew in surface water. Membranes in RO plants using this unchlorinated well water could then become fouled with S. typhi. RO plants, which are common throughout Saudi Arabia, need close monitoring. Water for RO must be prechlorinated to prevent microbiologic fouling of the membranes.

Major impediments to measles elimination. The modern epidemiology of an ancient disease.

Great success has been achieved in controlling measles in the United States with a greater than 99% reduction in incidence rate from the prevaccine era. However, since 1981, the incidence rate of measles in the United States has been relatively stable at approximately 1,500 to 3,000 reported cases annually. We reviewed available information to determine the remaining impediments to elimination of measles. The potential impediments can be divided into two categories: (1) implementation of the current strategy and (2) whether the current strategy needs modification. The major reason for the failure to achieve elimination appears to be the fact that some persons for whom vaccine is indicated have not been vaccinated. While vaccine failures and importations play a role in transmission, sustained transmission in a totally vaccinated community has not been demonstrated. All chains of transmission have involved some unvaccinated persons. Measles elimination will require complete implementation of current strategies and careful monitoring of epidemiologic trends to determine whether future modifications in strategy are needed.