Rocahepevirus ratti genotype 1 (rHEV), commonly known as rat hepatitis E virus, is a recently identified cause of viral hepatitis. We compared rHEV infections with conventional hepatitis E and measured rHEV seroprevalence in a large diverse human serum cohort. Patients with hepatitis (n=2018) were tested for rHEV RNA in the context of a real-world clinical service in Hong Kong. rHEV IgG seroprevalence in various risk groups were measured using a validated immunoassay. Commensal rats were tested for rHEV RNA and sequences were compared with human-derived strains. From 2017-2025, 22 human rHEV infections were identified. Of these, 14 (63·6%) were immunocompromised compared to 22/78 (28·2%) conventional HEV patients (p<0.01). Hepatitis was milder in rHEV patients, but most immunocompromised rHEV patients progressed to chronic infection. Rat-derived rHEV belonged to two subtypes, one of which infected humans. Of 8294 individuals, 57 (0·7%) tested positive for rHEV IgG compared to 551 (6·6%) for HEV IgG. Increasing age predicted rHEV seropositivity (OR:1·03; 95% CI:1·01-1·05); persons with bloodborne pathogens did not exhibit higher rHEV seroprevalence. rHEV is a sporadic cause of hepatitis in humans with disproportionate clinical significance for immunocompromised hosts. Although clearly linked to rat epizootics, routes of rHEV transmission remain enigmatic.

A post-COVID surge of Bordetella pertussis was observed globally. China has reported a high level of macrolide-resistant Bordetella pertussis (MRBP) in recent years; however, the epidemiology of MRBP in Hong Kong remains unknown. We retrieved archived B. pertussis isolates from respiratory samples collected at five regional public hospitals in Hong Kong between 2015 and 2024 and tested their minimum inhibitory concentration (MIC) for macrolides and other non-macrolide antibiotics using the Etest method. All isolates were also subjected to whole genome sequencing for genotypic resistance, Multi-locus Antigen Sequence Typing (MLST) and Multi-locus Variable Number of Tandem Repeat Analysis (MLVA) typing. Twenty-nine isolates of B. pertussis were included in the study. All isolates demonstrating phenotypic macrolide resistance harbored the A2047G mutation while showing low MIC to trimethoprim-sulfamethoxazole, doxycycline, levofloxacin, piperacillin-tazobactam and meropenem. In 2023 and 2024, 100% were MRBP and all belonged to the MT28 clone with the ptxP3 antigenic type. The MRBP isolates in Hong Kong were phylogenetically related to those from mainland China during the same period. There was no obvious correlation between macrolide resistance and clinical presentation, laboratory findings, management and outcome. Phylogenetic analysis suggests that MRBP isolates in Hong Kong and mainland China are closely related.