Cross-species transmission

Cross-species transmission (CST), also called interspecies transmission, host jump, or spillover, is the transmission of an infectious pathogen, such as a virus, between hosts belonging to different species. Once introduced into an individual of a new host species, the pathogen may cause disease for the new host and/or acquire the ability to infect other individuals of the same species, allowing it to spread through the new host population.^[1] The phenomenon is most commonly studied in virology, but cross-species transmission may also occur with bacterial pathogens or other types of microorganisms.^[2]

Steps involved in the transfer of pathogens to new hosts include contact between the pathogen and the host; the successful infection of an initial individual host, which may lead to amplification and an outbreak; and the adaptation of the pathogen, within either the original or new host, which may render it capable of spreading efficiently between individuals in populations of the new host.^[3] The concept is important in understanding and controlling emerging infectious diseases in humans, especially those caused by viruses. Most viral diseases of humans are zoonotic in origin, having been historically transmitted to human populations from various animal species; examples include SARS, Ebola, swine flu, rabies, and avian influenza.^[4]

The exact mechanisms which facilitate cross-species transmission vary by pathogen, and even for common diseases are often poorly understood. It is believed that viruses with high mutation rates are able to rapidly adapt to new hosts and thereby overcome host-specific immunological defenses, allowing their continued transmission. A host shifting event occurs when a strain that was previously zoonotic begins to circulate exclusively among the new host species.^[5]

Pathogen transfer is most likely to occur between species which are frequently in close contact with each other. It can also occur indirectly between species with less frequent contact if facilitated by an intermediary species; for example, a reservoir species may transfer the virus to a vector species, which in turn transfers the virus to humans.^[6]^[7] The degree of phylogenetic relatedness between host species also influences the likelihood that a pathogen is transmitted between them, likely because of the similarity of the hosts' immunological defenses; for example, most human zoonotic transmissions come from other species of mammals. Pathogens of more distantly related species, on the other hand, such as plant viruses, may not be capable of infecting humans at all. Other factors influencing transmission rates include geographic proximity and intraspecies behaviors.^[3] Due to climate change and habitat loss owing to land use expansion,^[8] the risk of viral spillover is predicted to significantly increase.^[9]

^ Childs JE, Mackenzie JE, Richt JE (2007), Wildlife and Emerging Zoonotic Diseases: The Biology, Circumstances and Consequences of Cross-Species Transmission, Current Topics in Microbiology and Immunology, vol. 315, Springer-Verlag Berlin Heidelberg: Springer Science+Business Media, pp. 129–134, doi:10.1007/978-3-540-70962-6, ISBN 978-3-540-70961-9
^ Benavides JA, Cross PC, Luikart G, Creel S (2014), "Limitations to estimating bacterial cross-species transmission using genetic and genomic markers: Inferences from simulation modeling", Evolutionary Applications, 7 (7): 774–787, Bibcode:2014EvApp...7..774B, doi:10.1111/eva.12173, PMC 4227858, PMID 25469159
^ ^a ^b Parrish CR, Holmes EC, Morens DM, Park EC, et al. (2008), "Cross-Species Virus Transmission and the Emergence of New Epidemic Diseases", Microbiol. Mol. Biol. Rev., 72 (3): 457–470, doi:10.1128/MMBR.00004-08, PMC 2546865, PMID 18772285
^ Faria NR, Suchard MA, Rambaut A, Streicker DG, et al. (2013), "Simultaneously reconstructing viral cross-species transmission history and identifying the underlying constraints", Philos Trans R Soc Lond B Biol Sci, 368 (1614): 20120196, doi:10.1098/rstb.2012.0196, PMC 3678322, PMID 23382420
^ Haven J, Park AW (2013), "Superinfection reconciles host–parasite association and cross-species transmission", Theoretical Population Biology, 90: 129–134, doi:10.1016/j.tpb.2013.09.015, PMC 7126234, PMID 24161558
^ Wang LF, Anderson DE (2019). "Viruses in bats and potential spillover to animals and humans". Current Opinion in Virology. 34: 79–89. doi:10.1016/j.coviro.2018.12.007. PMC 7102861. PMID 30665189.
^ Fagre AC, Kading RC (2019). "Can Bats Serve as Reservoirs for Arboviruses?". Viruses. 11 (3): 215. doi:10.3390/v11030215. PMC 6466281. PMID 30832426.
^ von Csefalvay C (2023), "Host-vector and multihost systems", Computational Modeling of Infectious Disease, Elsevier, pp. 121–149, doi:10.1016/b978-0-32-395389-4.00013-x, ISBN 978-0-323-95389-4, retrieved 2023-03-02
^ Carlson CJ, Albery GF, Merow C, Trisos CH, Zipfel CM, Eskew EA, Olival KJ, Ross N, Bansal S (28 April 2022). "Climate change increases cross-species viral transmission risk". Nature. 607 (7919): 555–562. Bibcode:2022Natur.607..555C. doi:10.1038/s41586-022-04788-w. ISSN 1476-4687. PMID 35483403. S2CID 248430532.

[Childs-1] Childs JE, Mackenzie JE, Richt JE (2007), Wildlife and Emerging Zoonotic Diseases: The Biology, Circumstances and Consequences of Cross-Species Transmission, Current Topics in Microbiology and Immunology, vol. 315, Springer-Verlag Berlin Heidelberg: Springer Science+Business Media, pp. 129–134, doi:10.1007/978-3-540-70962-6, ISBN 978-3-540-70961-9

[Benavides-2] Benavides JA, Cross PC, Luikart G, Creel S (2014), "Limitations to estimating bacterial cross-species transmission using genetic and genomic markers: Inferences from simulation modeling", Evolutionary Applications, 7 (7): 774–787, Bibcode:2014EvApp...7..774B, doi:10.1111/eva.12173, PMC 4227858, PMID 25469159

[Parrish-3] Parrish CR, Holmes EC, Morens DM, Park EC, et al. (2008), "Cross-Species Virus Transmission and the Emergence of New Epidemic Diseases", Microbiol. Mol. Biol. Rev., 72 (3): 457–470, doi:10.1128/MMBR.00004-08, PMC 2546865, PMID 18772285

[Faria-4] Faria NR, Suchard MA, Rambaut A, Streicker DG, et al. (2013), "Simultaneously reconstructing viral cross-species transmission history and identifying the underlying constraints", Philos Trans R Soc Lond B Biol Sci, 368 (1614): 20120196, doi:10.1098/rstb.2012.0196, PMC 3678322, PMID 23382420

[Haven-5] Haven J, Park AW (2013), "Superinfection reconciles host–parasite association and cross-species transmission", Theoretical Population Biology, 90: 129–134, doi:10.1016/j.tpb.2013.09.015, PMC 7126234, PMID 24161558

[Wang2019-6] Wang LF, Anderson DE (2019). "Viruses in bats and potential spillover to animals and humans". Current Opinion in Virology. 34: 79–89. doi:10.1016/j.coviro.2018.12.007. PMC 7102861. PMID 30665189.

[Fagre2019-7] Fagre AC, Kading RC (2019). "Can Bats Serve as Reservoirs for Arboviruses?". Viruses. 11 (3): 215. doi:10.3390/v11030215. PMC 6466281. PMID 30832426.

[8] von Csefalvay C (2023), "Host-vector and multihost systems", Computational Modeling of Infectious Disease, Elsevier, pp. 121–149, doi:10.1016/b978-0-32-395389-4.00013-x, ISBN 978-0-323-95389-4, retrieved 2023-03-02

[Carlson-9] Carlson CJ, Albery GF, Merow C, Trisos CH, Zipfel CM, Eskew EA, Olival KJ, Ross N, Bansal S (28 April 2022). "Climate change increases cross-species viral transmission risk". Nature. 607 (7919): 555–562. Bibcode:2022Natur.607..555C. doi:10.1038/s41586-022-04788-w. ISSN 1476-4687. PMID 35483403. S2CID 248430532.

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