The effects of relative humidity and temperature on the survival of human rotavirus in a thin layer of faeces on an impervious surface and on absorbent material was investigated using the indirect immunofluorescence technique in LLC-MK2 cells to titrate infectivity. Rotavirus was found to be very stable at low and high relative humidities but not in the medium range of relative humidity. Rotavirus infectivity was lost more rapidly under all humidities at 37 degrees C than at 4 degrees or 20 degrees C.

We describe two enzyme-linked immunosorbent assays for rotavirus antigen in feces, which were designed to be as sensitive and specific as possible, and easy to use anywhere. Both are indirect methods, using the antibody capture method, but the second assay utilizes a rotavirus group-specific monoclonal "detecting" antibody instead of the hyperimmune polyvalent guinea pig antisera used in the first assay. Both tests weîe found to be more sensitive than electron microscopy for detecting virus. To develop these tests, solid phase, antiserum production methods, treatment of the test antigen with EDTA, substrate, stability of reagents, and the need for confirmatory "blocking" tests were all examined. The first assay described is that used at present by the World Health Organization for their worldwide diarrheal disease control program.

During July-August 1977, an outbreak of acute diarrhea occurred in an unusually isolated population, the Tiriyó Indians, who live in the north of Pará, Brazil, near the border with Surinam. Diarrhea was reported by 157 (70%) of the 224 Indians living in the village during the epidemic. There was one fatal case in a one year old child. Rotavirus was detected by electron microscopy in one fecal specimen collected from an acute case of diarrhea. Seroconversions were noted in 127 out of 168 (75.6%) paired serum samples tested for rotavirus antibody by counter-immunoelectrophoresis. With immunofluorescence based neutralization tests, rotavirus serotype 1 (Birmingham) was shown to be associated with the outbreak. The infection also boosted type 3 antibodies but this was most apparent in persons with pre-existing type 3 titers and the boost was not as great as with type 1. All age groups were affected. The proportion symptomatic was greatest in young children.

Sera from inhabitants of Belém, Pará (542 sera), Brazil and of members of 3 Brazilian tribes--Tiriyo/Alto Paru (near Surinam) (212 sera), Xicrin (128 sera), and Mekranoiti (121 sera)--of different age and sex groups were tested for the presence of specific antibody against human parvovirus (B19) (RIA) and rubella virus (latex agglutination test). Parvovirus (B19) IgG was found in 42.6% of the population sample from Belém but in only 4.7 to 10.7% of the members of the tribes. Rubella virus antibody was found in 72.7% of the sera from Belém but approaching a prevalence of 85-90% in age groups above 20 years. In the tribes rubella virus antibody was detected in 36.9 to 72.6% of all sera. There were remarkable sex differences of antibody prevalence in several age groups of the population from Belém and of the tribal populations. About a quarter of the skin rashes in Belém that were not attributable to infections with rubella, measles, or arboviruses were caused by recent B19 infections.

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