What is the risk of a deadly adenovirus pandemic?

Abstract

Many of us had refresher courses in virology, immunology, and epidemiology in 2020, and we were reminded of the fact that Homo sapiens, the wiliest predator on the planet, has been hunting everything that moves for millennia. These repeated interspecies contacts inherently lead to recurrent zoonosis (nonhuman to human) and anthroponosis (human to nonhuman). Given the accelerating changes in our ecosystems since the neolithic revolution, it was not surprising to see a virus that spreads via aerosolization and liquid droplets cause a pandemic in a few months. The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic begs the question-which viruses could cause a global threat? In this Opinion, the characteristics that make adenoviruses a risk, which include efficient intra- and interspecies transmission, thermostable particles, persistent/latent infections in diverse hosts, and the ability to readily recombine and escape herd immunity, are discussed.

Fig 1. Many mammals have latent adenoviruses (red capsid in humans, green in monkeys, orange in bats) that are controlled by anti-adenovirus memory T cells in healthy hosts.

These viruses may have replicated and induced asymptomatic or mild disease in the respiratory or gastrointestinal tract. Notably, in primates, adenovirus types that generate respiratory tract infections are often shed via the gastrointestinal tract. When a host encounters another type (blue capsids) that propagates in the same tissue, the opportunity for recombination increases. If a recombination event gives a selective advantage (e.g., escape of immune surveillance, modified tissue tropism, and alternative receptors) to the new type (multicolored capsids), it can be passed to other individuals to reinitiate the same scenario. Mutations that increase the host range (e.g., in the DBP) also occur randomly and expand the reservoirs and increase the propensity for zoonotic and anthroponotic exchanges—and the creation of more virulent types. DBP, DNA-binding protein.