1.Human cases of Q fever in Northern California appear to be at least as frequently associated with contact with sheep and goats as with cattle.
2.Serologic studies, however, indicate that infection with C. burneti is much more prevalent in sheep (37.9 per cent) and goats (43.6 per cent) epidemiologically linked with human cases, than in cattle similarly associated with human infections.
3.Serologic surveys of the general sheep and cattle population, as sampled through animals received at slaughterhouses, indicate that the extent of infection in this group is small; 3.1 per cent of the cows and calves and 3.5 per cent of the sheep examined were found to possess antibodies. Too few data on goats were available for analysis.
4.The serologic data indicate that infections in man, sheep and quite probably goats, are epidemiologically related.
5.That the role of sheep and goats in the epidemiology of the human disease is important finds additional support in the demonstration that the rickettsia is excreted in the milk of these species.
6.The possibility of air-borne transmission of Q fever is considered and discussed.