Outbreaks of nosocomial feline calicivirus-associated virulent systemic disease in Korea.

Importance: Feline calicivirus (FCV)-associated viral systemic disease (VSD) is a severe systemic disease caused by virulent FCV strains and has a very poor prognosis.

Objective: To evaluate the clinical characteristics of a nosocomial FCV-VSD outbreak involving 18 cats in Korea.

Methods: Medical records of cats diagnosed with FCV-VSD from March to September 2018 at a referral veterinary hospital were reviewed. The patient's signalment, history, clinical features, diagnosis, treatment, and prognosis were evaluated.

Results: Two outbreaks involving 18 cats diagnosed with FCV-VSD occurred over a 6-month period at a referral hospital in Korea. Anorexia, lethargy, fever, and limb edema were the most commonly observed clinical symptoms. Lymphopenia and macrothrombocytopenia were the most common hematological findings, and hyperbilirubinemia and increased levels of aspartate aminotransferase, creatine kinase, and serum amyloid A were the most frequent results of serum biochemistry. FCV was detected by reverse transcription polymerase chain reaction in 11 patients and the remaining 7 were suspected with FCV-VSD. The overall mortality rate was 72.2%. The hospital was closed and disinfected twice, and no additional outbreaks have occurred since the last patient.

Conclusions and relevance: The clinical and diagnostic characteristics and outcomes of FCV-VSD described in this study can be used to recognize and contain infectious diseases through quick action. To the best of the authors' knowledge, this is the first report of a nosocomial outbreak of FCV-VSD in Asia.