Here, is the day of implementation of enhanced hygiene measures, G is the cumulative probability function of the generation time distribution, h t ρ is the relative reduction of the reproduction number due to implementation of hygiene measures and is the effective reproduction number without enhanced hygiene measures. u R Polyomaviruses KI and WU in Immunocompromised Patients with Respiratory Disease Polyomaviruses KI (KIPyV) and WU (WUPyV) were recently identified, mainly in respiratory specimens from children. Among 200 patients with respiratory disorders admitted to Saint Louis Hospital, Paris, France, KIPyV was detected in 8% and WUPyV in 1%. KIPyV was significantly more frequent among human stem cell transplant patients (17.8% vs. 5.1%; p = 0.01). R ecently, 2 new, distinct polyomaviruses (PyVs), KI (KIPyV) and WU (WUPyV), were identifi ed in respiratory specimens, mainly from children <5 years of age with respiratory tract infections. The fi rst retrospective studies of respiratory specimens in Sweden and Australia showed a KIPyV prevalence of 1% and 2.5%, respectively (1, 2) . Studies conducted in Australia and the United States showed a WUPyV prevalence in respiratory specimens of 3% and 0.7%, respectively (3) . Further studies conducted in Canada and South Korea have shown similar frequencies (4, 5) . In this study, we examined the prevalence of KIPyV and WUPyV in immunocompromised patients with suspected respiratory tract infections.