The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has reached nearly every country in the world with extraordinary person-to-person transmission. The most likely original source of the virus was spillover from an animal reservoir and subsequent adaptation to humans sometime during the winter of 2019 in Wuhan Province, China. Because of its genetic similarity to SARS-CoV-1, it is probable that this novel virus has a similar host range and receptor specificity. Due to concern for human–pet transmission, we investigated the susceptibility of domestic cats and dogs to infection and potential for infected cats to transmit to naive cats. We report that cats are highly susceptible to infection, with a prolonged period of oral and nasal viral shedding that is not accompanied by clinical signs, and are capable of direct contact transmission to other cats. These studies confirm that cats are susceptible to productive SARS-CoV-2 infection, but are unlikely to develop clinical disease. Further, we document that cats developed a robust neutralizing antibody response that prevented reinfection following a second viral challenge. Conversely, we found that dogs do not shed virus following infection but do seroconvert and mount an antiviral neutralizing antibody response. There is currently no evidence that cats or dogs play a significant role in human infection; however, reverse zoonosis is possible if infected owners expose their domestic pets to the virus during acute infection. Resistance to reinfection holds promise that a vaccine strategy may protect cats and, by extension, humans.

The recent emergence of both chikungunya and Zika viruses in the Americas has significantly expanded their distribution and has thus increased the possibility that individuals may become infected by more than one Aedes aegypti-borne virus at a time. Recent clinical data support an increase in the frequency of coinfection in human patients, raising the likelihood that mosquitoes could be exposed to multiple arboviruses during one feeding episode. The impact of coinfection on the ability of relevant vector species to transmit any of these viruses (that is, their vector competence) has not been determined. Thus, we here expose Ae. aegypti mosquitoes to chikungunya, dengue-2 or Zika viruses, both individually and as double and triple infections. Our results show that these mosquitoes can be infected with and can transmit all combinations of these viruses simultaneously. Importantly, infection, dissemination and transmission rates in mosquitoes are only mildly affected by coinfection.

West Nile virus (WNV) continues to be a major cause of human arboviral neuroinvasive disease. Susceptible non-human vertebrates are particularly diverse, ranging from commonly affected birds and horses to less commonly affected species such as alligators. This review summarizes the pathology caused by West Nile virus during natural infections of humans and non-human animals. While the most well-known findings in human infection involve the central nervous system, WNV can also cause significant lesions in the heart, kidneys and eyes. Time has also revealed chronic neurologic sequelae related to prior human WNV infection. Similarly, neurologic disease is a prominent manifestation of WNV infection in most non-human non-host animals. However, in some avian species, which serve as the vertebrate host for WNV maintenance in nature, severe systemic disease can occur, with neurologic, cardiac, intestinal and renal injury leading to death. The pathology seen in experimental animal models of West Nile virus infection and knowledge gains on viral pathogenesis derived from these animal models are also briefly discussed. A gap in the current literature exists regarding the relationship between the neurotropic nature of WNV in vertebrates, virus propagation and transmission in nature. This and other knowledge gaps, and future directions for research into WNV pathology, are addressed.

Arboviruses such as Zika virus (ZIKV, Flaviviridae; Flavivirus) must replicate in both mammalian and insect hosts possessing strong immune defenses. Accordingly, transmission between and replication within hosts involves genetic bottlenecks, during which viral population size and genetic diversity may be significantly reduced. To help quantify these bottlenecks and their effects, we constructed 4 "barcoded" ZIKV populations that theoretically contain thousands of barcodes each. After identifying the most diverse barcoded virus, we passaged this virus 3 times in 2 mammalian and mosquito cell lines and characterized the population using deep sequencing of the barcoded region of the genome. C6/36 maintain higher barcode diversity, even after 3 passages, than Vero. Additionally, field-caught mosquitoes exposed to the virus to assess bottlenecks in a natural host. A progressive reduction in barcode diversity occurred throughout systemic infection of these mosquitoes. Differences in bottlenecks during systemic spread were observed between different populations of Aedes aegypti.

12The pandemic caused by SARS-CoV-2 has reached nearly every country in the world with 13 extraordinary person-to-person transmission. The most likely original source of the virus was 14 spillover from an animal reservoir and subsequent adaptation to humans sometime during the 15 winter of 2019 in Wuhan Province, China. Because of its genetic similarity to SARS-CoV-1, it is 16 likely that this novel virus has a similar host range and receptor specificity. Due to concern for 17 human-pet transmission, we investigated the susceptibility of domestic cats and dogs to infection 18 and potential for infected cats to transmit to naïve cats. We report that cats are highly susceptible 19 to subclinical infection, with a prolonged period of oral and nasal viral shedding that is not 20 accompanied by clinical signs, and are capable of direct contact transmission to other cats. These 21 studies confirm that cats are susceptible to productive SARS-CoV-2 infection, but are unlikely to 22 develop clinical disease. Further, we document that cats develop a robust neutralizing antibody 23 response that prevented re-infection to a second viral challenge. Conversely, we found that dogs 24 do not shed virus following infection, but do mount an anti-viral neutralizing antibody response. 25There is currently no evidence that cats or dogs play a significant role in human exposure; 26 however, reverse zoonosis is possible if infected owners expose their domestic pets during acute 27 infection. Resistance to re-exposure holds promise that a vaccine strategy may protect cats, and 28 by extension humans, to disease susceptibility. 29 30 Introduction 31 32 The COVID-19 pandemic, caused by the SARS-CoV-2 (SARS2) coronavirus, originated in the 33 Wuhan province of China, in late 2019 and within four months spread to nearly every country in 34 the world. Sequence analysis and epidemiological investigations suggest that the virus was of 35 animal-origin, possibly bat, and was first introduced into the human population via an 36 intermediate animal host in the Huanan seafood market in Wuhan, China (Bogoch et al. 2020; 37 Zhou et al. 2020). The virus quickly adapted to humans and human-to-human transmission 38 became the almost immediate source of subsequent infections, with direct contact and aerosol 39 droplets as the primary routes of infection (Li et al. 2020). Early indications suggested that 40 SARS2, much like SARS-CoV-1 (SARS1), infects host cells by binding to the angiotensin-41 converting enzyme 2 (ACE2), a receptor that is expressed in many animal species, although 42 notably not in mice or rats (Wan et al. 2020). Thus, while humans are almost certainly the sole 43 source of infection to other humans, multiple early studies suggest other animals are susceptible 44 to infection as well. 129 130 Dogs (n=3) 131 Dogs were sampled at the same frequency, and using the same methods as cats in Cohort 1 for 132 42 days post-infection. Dogs were not re-challenged. 133 134 Clinical observations 135 Body temperatures were recorded daily for the dur...