Acute hepatitis caused by a novel strain of hepatitis E virus most closelyrelated to United States strains

A unique hepatitis E virus (HEV) strain was identified as the aetiological agent of acute hepatitis in a United States (US) patient who had recently r eturned from vacation in Thailand, a country in which HEV is endemic. Seque nce comparison showed that this HEV strain was most similar, but not identi cal, to the swine and human HEV strains recovered in the US. Phylogenetic a nalysis revealed that this new HEV isolate was closer to genotype 3 strains than to the genotype 1 strains common in Asia. The fact that this HEV was closely related to strains recovered in countries where HEV is not endemic and was highly divergent from Asian HEV strains raises the questions of whe re the patient's infection was acquired and of whether strains are geograph ically as localized as once thought.