In December 1997, 170 hemorrhagic fever-associated deaths were reported in Carissa District, Kenya. Laboratory testing identified evidence of acute Rift Valley fever virus (RVFV). Of the 171 persons enrolled in a cross-sectional study, 31(18%) were anti-RVFV immunoglobulin (Ig) M positive. An age-adjusted IgM antibody prevalence of 14% was estimated for the district. We estimate approximately 27,500 infections occurred in Garissa District, making this the largest recorded outbreak of RVFV in East Africa. In multivariate analysis, contact with sheep body fluids and sheltering livestock in one’s home were significantly associated with infection. Direct contact with animals, particularly contact with sheep body fluids, was the most important modifiable risk factor for RVFV infection. Public education during epizootics may reduce human illness and deaths associated with future outbreaks.

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ERGOSTEROL, ERGOCALCIFEROL AND GLYCOLYSIS 609 slices, appear for both male and female animals. Glover et al. (1952) found that after administration of 7-dehydrocholesterol to guinea pigs, the substance had a 'transient existence' in the liver. Tuboi (1948), perfused rabbit liver with ergosterol and 7-dehydrocholesterol, when these substances disappeared, and gave rise to cholic and deoxycholic acids in each case. These acids do not show selective absorption in the region of 290 me., so that the maximum at 290 mIL. may be due to an intermediate in the conversion of ergosterol into the acids. SUMMARY 1. The use of propylene glycol, Tween 80 and lecithin for producing aqueous solutions of ergosterol has been investigated. 2. The effect of the above substances on the anaerobic glycolysis rate of rat-liver slices has been studied: 0.01 % (v/v) Tween 80 and 1 % propylene glycol show appreciable inhibition of glycolysis, whereas lecithin up to 0-36 % has no effect. 3. Solutions of ergosterol and ergocalciferol in aqueous lecithin have been used to investigate the effect of these sterols on the anaerobic glycolysis rate of rat-liver slices; there is increasing inhibition of glycolysis with concentration, for the range 10-3-102 /zg./ml., ergosterol having a greater effect on male tissue, and ergocalciferol a greater effect on female tissue. 4. The spectra of aqueous ergosterol and ergocalciferol solutions have been investigated, after incubation with rat-liver slices.

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RAPID SPECTROPHOTOMETRY 171 which they are subjected can result in cutting into and fragmentation of the surface of the valve tips. Finally, the 20 mm. observation tube described is not the only device that can be employed with the apparatus; the separation of the mixers from the observation tube makes it possible to use any recording device that can be introduced into the space between the mixer and the stop block. Alternative arrangements for following bioluminescent reactions (Gibson & Hastings, 1962) and fluorescence changes (Hastings & Gibson, 1963) have already been described and there is no reason why conductivity, pH or oxygen concentration should not also be followed with suitable equipment. SUMMARY 1. The construction of a stopped-flow apparatus for following rapid reactions with half-times from 5 msec. upwards is described. 2. Some details of performance and suggestions for operation and maintenance are given.