Prevalence and molecular epidemiology of human coronavirus HKU1 in patients with acute respiratory illness.

In 2005, human coronavirus HKU1 (HCoV-HKU1) was isolated and identified from a 71-year-old man with pneumonia in Hong Kong. To identify and classify genotypes of HCoV-HKU1 in Korea, a sensitive, specific, and quantitative real-time polymerase chain reaction (PCR) assay was developed and analyzed the sequences of HCoV-HKU1 isolated in Korea. A total of 1,985 respiratory specimens taken from patients with acute respiratory illness were tested for HCoV-HKU1 from January 2007 to May 2008. The major clinical symptoms associated with HCoV-HKU1 infection were examined statistically and sequence variations of the RNA-dependent RNA polymerase (RdRp), spike, and nucleocapsid genes were also analyzed. Fifty cases (2.5%) HCoV-HKU1 were identified by real-time PCR and viral loads ranged from 6.7 × 10(4) to 1.6 × 10(9)  copies/ml. The clinical symptoms of HCoV-HKU1 infection included rhinorrhea (72%), cough (64%), nasal congestion (56%), fever (32%), sputum (30%), sore throat (18%), chills (16%), postnasal discharge (14%), and tonsillar hypertrophy (10%). There was a seasonal distribution of HCoV-HKU1 infection, peaking in winter and spring. Both genotypes A and B were detected but no recombination between them was found. This is the first report on the identification and genotyping of HCoV-HKU1 as a causative agent of acute respiratory illness in Korea. The data suggest that at least two genotypes, A and B, of HCoV-HKU1 with scattered silent mutations were circulating in Korea from 2007 to 2008.