Wayne H. Thompson

Topical Review: La Crosse and Other Forms of California Encephalitis:

The California serogroup viruses are mosquito viruses that cause human infections on five continents. They are maintained and amplified in nature by a wide variety of mosquito vectors and mammalian hosts; they thrive in a remarkably wide variety of microclimates (eg, tropical, coastal temperate marshland, lowland river valleys, alpine valleys and highlands, high boreal deserts, and arctic steppes). In 1993, California serogroup viruses caused 71% of all cases of arboviral illness in the United States, principally La Crosse encephalitis.1 The 30 to 180 annual cases of La Crosse encephalitis represent 8% to 30% of all cases of encephalitis, rendering this illness the most common and important endemic mosquito-borne illness in the USA. Subclinical or mild infections are much more common. Methods and results acquired from intense study of California serogroup viruses have been applied, with benefit, to the study of the ecology and pathogenesis of many more serious human arboviral illnesses. The evolutionary potential of viruses, with particular reference to the development of more virulent strains, has been studied more closely in the California serogroup viruses than in almost any other agent of human disease. (J Child Neurol 1999;14:1-14).

California arbovirus encephalitis in children.

UNTIL RECENT YEARS three principal arboviruses, Eastern, Western, and St. Louis, have been associated with human encephalitis in the United States. Since 1964, a considerable number of symptomatic cases of encephalitis associated with California encephalitis virus (C.E.V.) infections have been reported from this country, primarily from Wisconsin and other Midwestern states. It has been the most common arthropod-borne viral infection found in Wisconsin residents. This paper reports clinical and follow-up studies of 35 children with central nervous system disease associated with California encephalitis group virus infection.