Evidence of Reverse Zoonotic Transmission of Human Seasonal Influenza A Virus (H1N1, H3N2) Among Cats

Abstract Background Pandemic COVID-19 disease represents a challenge for health-care structures and the molecular confirmation of samples from infected individuals is crucial and therefore guides public health decision making. Clusters and possibly increased diffuse transmission could occur in the context of the next influenza season. For this reason, a diagnostic test able to discriminate SARS-CoV-2 from influenza viruses is urgently needed. Methods A multiplex rt-Real Time PCR assay was assessed using one laboratory protocol with different Real Time PCR instruments. Overall, 1,000 clinical samples (600 samples SARS-CoV-2 infected patients, 200 samples from influenza infected patients and 200 negative samples) were analyzed. Results The assay developed was able to detect and discriminate each virus target, and to intercept co-infections. The limit of quantification of each assay ranged between 5 and 10 genomic copy numbers, with a cutoff value of 37.7 and 37.8 for influenza and SARS-CoV-2 viruses, respectively. Only two influenza co-infections were detected in COVID-19 samples. Conclusions This study suggests that multiplex assay is a rapid, valid, and accurate method for the detection of SARS-CoV-2 and influenza viruses in clinical samples. The test may be an important diagnostic tool for both diagnostic and surveillance purposes during the seasonal influenza activity period.

Background The close contact between cats and humans poses a threat to public health because of the potential zoonotic transmission of influenza viruses to humans. Therefore, we examined the seroprevalence of pandemic H1N1/09, canine H3N2, and human H3N2 viruses in pet cats in northern China from 2010 to 2014. Finding Of 1794 serum samples, the seropositivity rates for H1N1/09, canine H3N2, and human H3N2 were 5.7%, 0.7%, and 0.4%, respectively. The seropositivity rate for H1N1/09 in cats was highest in 2010 (8.3%), and then declined continuously thereafter. Cats older than 10 years were most commonly seropositive for the H1N1/09 virus. Conclusions Our findings emphasize the need for continuous surveillance of influenza viruses in cats in China.

The term reverse zoonosis specifically refers to the natural transmission of disease and infection from humans to animals, with humans as the reservoir host replicating the infectious agent. In the last 20 years, reverse zoonosis has increasingly garnered attention because of human disease outbreaks. In this Currents in One Health article, the author will review host range as the main risk factor for reverse zoonosis, with an emphasis on influenza A virus (IAV) disease events in humans and other species in the context of a “One Health” approach to gain a better understanding of their transmission routes to facilitate their control and prevent them from occurring. The human-to-pig transmission of IAV represents the largest reverse zoonosis of a pathogen documented to date. At the same time, the 2022 farmed mink outbreak in Spain is the most sustained mammal-to-mammal transmission of the highly pathogenic avian influenza (HPAI) H5N1 since its re-emergence in humans in 2003. Without any prospect of eradicating IAVs, the best way to mitigate the impact of IAV reverse zoonosis is by vaccinating humans and susceptible farmed and pet animals. The recent major reverse zoonoses involving other virus groups ( Coronaviridae, Poxviridae , arboviruses, and the human respiratory viruses transmitted to endangered non-human primate species) and the prevention and control of reverse zoonoses are addressed in the companion Currents in One Health by Kibenge, JAVMA , June 2023.