In 1999, a mysterious outbreak of human encephalitis occurred in the northeastern United S...

In 1999, a mysterious outbreak of human encephalitis occurred in the northeastern United States. The cause was tentatively identified as St. Louis encephalitis virus. At the same time, an unusual number of dead birds were noticed along the northeastern Atlantic coast. Figure shows genetic relationships of three known encephalitis viruses (St. Louis, Japanese, and West Nile) and several viruses iso-lated from the birds, from two human patients that died, from one dead horse, and from mosquitoes. (Data compiled from Anderson et al. 1999 and Lanciotti et al. 1999.)

Figure A phylogeny of encephalitis viruses isolated from various hosts in the northeasternUnited States during 1999 Based on data and analyses in Anderson et al. (1999) and Lanciotti et al. (1999).

a. Were the birds, the horse, and the humans all sufferingfrom the same disease?

b. Do you think the outbreak was caused by St. Louis encephalitis virus?

c. Does this cladogram suggest how the disease might be spread?