Yellow Fever Virus Infectivity for BolivianAedes aegyptiMosquitoes

The absence of urban yellow fever virus (YFV) in Bolivian cities has been attributed to the lack of competent urban mosquito vectors.Experiments with Aedes aegypti from Santa Cruz, Bolivia, demonstrated infection (100%), dissemination (20%), and transmission of a Bolivian YFV strain (CENETROP-322).Y ellow fever virus (YFV) may cause severe hemor- rhagic fever in humans.The virus is transmitted between susceptible vertebrate hosts by infected mosquitoes in the genera Aedes, Haemagogus, or Sabethes (1).In the Americas, YFV occurs in two transmission cycles.In the jungle/sylvatic cycle, the virus is transmitted between susceptible monkeys, and possibly other vertebrates, by tree-hole-breeding mosquitoes (1).Jungle yellow fever (YF) cases occur when these infected vectors feed on susceptible humans.In the urban cycle, YFV is transmitted to humans by Aedes aegypti mosquitoes (1).In 2003, a total of 226 cases of jungle YF were reported from South America to the Pan American Health Organization, and as of June 23, ongoing outbreaks in Bolivia, Brazil, Colombia, and Peru during 2004 have thus far resulted in 86 confirmed cases and 41 deaths ( 2).An Ae. aegypti eradication campaign initiated by the Pan American Sanitary Bureau in 1947 eliminated this species from most of Central and South America, and urban YF disappeared from the Americas in the 1940s.However, during the past 20 years, many countries abandoned Ae. aegypti control measures, and this urban vector now reoccupies almost the entire area of its distribution preeradication (1).Ae. aegypti was eradicated from Bolivia during the 1960s and 1970s but reappeared in the city of Santa Cruz in 1980, and epidemics of dengue fever occurred during the 1980s and 1990s (3).In 1997 to 1998, six cases of YF were reported among Santa Cruz residents, and some were regarded as urban YF cases (3); despite a population >1 million, low vaccine immunization cover-