The role of cats is of particular interest, because they are in close contact with humans and frequently in contact with other cats.
Available field (2-9) and experimental data (10-14) indicate that cats are susceptible to infection, occasionally show mild clinical signs and 43 may be able to transmit the infection between cats. Indeed, transmission experiments confirmed this possibility (10-14), however, the lack of a proper statistical assessment of transmission in the reported experiments limits confident extrapolation of the results from the experiment to the population. An important question when assessing the risk of transmission is whether cat-to-cat transmission can be sustained. The former experiment assessed droplet-transmission whilst the latter two experiments assessed direct transmission and allowed confirmation that R0is significantly higher than 1 (p < 0.05). When combining these two experiments, theestimated R0 (T * β) for cats was 3.9 (95% 110 confidence intervals: 2.2 – 6.8) or 3.3 (FSM) (1.1 – 11.8). These estimates were similar to the estimates done at household level, with the estimated R0 (FSM) being 3.8 (1.2 – 42.2) Interestingly, levels of virus shedding in household infected cats, were as high as those observed experimentally (Table 3), with reported shedding levels as high as 10(8.5) RNA copies/swab sample or RT-PCR CT values as low as 21. Considering both that infected cats shed high levels of virus, and that droplet transmission is possible, the risk for cat- to-human transmission of SARS-CoV-2 may not be low.