To identify the epidemiological and genetic characteristics of norovirus (NoV) outbreaks and estimate the impact of NoV infections in an older population, we analysed epidemiological and laboratory data collected using standardized methods from long-term care facilities (LTCFs) during 2003-2006. Faecal specimens were tested for NoV by real-time reverse transcriptase-polymerase chain reaction. NoV strains were genotyped by sequencing. Of the 234 acute gastroenteritis (AGE) outbreaks reported, 163 (70%) were caused by NoV. The annual attack rate of outbreak-associated NoV infection in LTCF residents was 4%, with a case-hospitalization rate of 3·1% and a case-fatality rate of 0·5%. GII.4 strains accounted for 84% of NoV outbreaks. Median duration of illness was longer for GII.4 infections than non-GII.4 infections (33 vs. 24 h, P<0·001). Emerging GII.4 strains (Hunter/2004, Minerva/2006b, Terneuzen/2006a) gradually replaced the previously dominant strain (Farmington Hills/2002) during 2004-2006. NoV GII.4 strains are now associated with the majority of AGE outbreaks in LTCFs and prolonged illness in Oregon.

From Drs. Stovall and Bubolz 91 Monilia type I 92 Monilia type II 93 Monilia type III From Drs. Langeron and Talice 46 Mycotorula p8ilosis Their no. 340 44 Mycotoruloides ovali8 Their no. 296 C-70 Geotrichoides Krusei Their no. 683 49 Candida tropicalis Their no. 255 C-76 Candida parapsilosis Their no. 341 171 Blastodendrion intermedium Their no. 493 47 Mycocandida mortifera Their no. 516 From Drs. Reed and Johnstone 238 Monilia type II. 239 Monilia type III 240 Monilia type IV 242 Monilia type VI-METHODS OF IDENTIFICATION