Virological factors that increase the transmissibility of emerging human viruses

Abstract

The early detection of pathogens with epidemic potential is of major importance to public health. Most emerging infections result in dead-end "spillover" events in which a pathogen is transmitted from an animal reservoir to a human but is unable to achieve the sustained human-to-human transmission necessary for a full-blown epidemic. It is therefore critical to determine why only some virus infections are efficiently transmitted among humans whereas others are not. We sought to determine which biological features best characterized those viruses that have achieved sustained human transmission. Accordingly, we compiled a database of 203 RNA and DNA human viruses and used an information theoretic approach to assess which of a set of key biological variables were the best predictors of human-to-human transmission. The variables analyzed were as follows: taxonomic classification; genome length, type, and segmentation; the presence or absence of an outer envelope; recombination frequency; duration of infection; host mortality; and whether or not a virus exhibits vector-borne transmission. This comparative analysis revealed multiple strong associations. In particular, we determined that viruses with low host mortality, that establish long-term chronic infections, and that are nonsegmented, nonenveloped, and, most importantly, not transmitted by vectors were more likely to be transmissible among humans. In contrast, variables including genome length, genome type, and recombination frequency had little predictive power. In sum, we have identified multiple biological features that seemingly determine the likelihood of interhuman viral transmissibility, in turn enabling general predictions of whether viruses of a particular type will successfully emerge in human populations.virus | evolution | transmission | comparative analysis | spill-over

Evolutionary biology of human hepatitis viruses

“…For example, chronic courses of viral infections in animal reservoirs were found to be a strong predictor of humanto-human transmissibility after zoonotic introduction into humans. 93 Here, we compare transmission routes, organ tropism, disease outcomes, receptor usage and immune evasion strategies among human and non-human hepatitis viruses.…”

Synergistic China–US Ecological Research is Essential for Global Emerging Infectious Disease Preparedness

“…Global-scale, government-sponsored EID preparedness efforts, initiated or supported to date by joint China-US partnerships, have focused on improving early-warning capabilities for known and novel human pathogens in both humans and animal reservoirs. These initiatives have included the US CDC Global Disease Detection program (CDC-GDDP), which has collaborated with China CDC and 10 other nations to develop international centers that help countries prevent, detect and respond to public health threats (Centers for Disease Control 2018); the US Agency for International Development's (USAID) Emerging Pandemic Threats (EPT) Program, which has collaborated with China CDC and Wuhan Institute of Virology and 29 other nations to strengthen EID preparedness through pathogen surveillance in wildlife, domestic animals and humans, risk characterization for pathogen spillover and One Health training and outreach; the WHO, OIE and FAO's collaborative global early-warning system for animal diseases transmissible to humans (GLEWS) (World Health Organization 2018); the China National Global Virome Initiative (CNGVI; part of the Global Virome Project (GVP Carroll et al 2018), a pathogen discovery project proposed to identify a large portion of the remaining undiscovered viruses (Carroll et al 2018;Mora et al 2011;Geoghegan et al 2016); and joint research supported by the US National Institutes of Health (NIH) to define the origin of SARS-and MERS-like coronaviruses (Luo et al 2018;Hu et al 2017) and identify other SARS coronavirus mammalian infections in China (Zhou et al 2018).…”

Zoonotic Potential of Emerging Paramyxoviruses

“…In fact, comparison with RNA viruses of other families suggests that paramyxoviruses may have relatively high rates and probabilities of transfer to new host species (Kitchen et al 2011). Moreover, such relative flexibility in host species, in addition to molecular traits of paramyxoviruses such as a non-segmented genome and non-vector transmission, has also been identified as a positive correlate of likelihood of human-to-human transmission of emerging zoonotic viruses following a spillover event (Anthony et al 2015; Geoghegan et al 2016). …”