Of virulent viruses and reservoir hosts

June 12, 2020
By: Jacob Shea
A panel of experts discussed the COVID-19 pandemic on Friday. (UC Berkeley video)

As the public health community races to contain the current global pandemic, researchers are working diligently to understand the novel coronavirus. Such efforts cross many facets of scientific research — from virology to wildlife ecology to medicine — with the ultimate hope of containing the virus and developing a vaccine.

Last Friday, two UC Berkeley researchers specializing in viruses took part in a more than hour-long Berkeley Conversations: COVID-19, a live, online video event put on by the Rausser College of Natural Resources and the Department of Plant and Microbial Biology, which is celebrating its 30th year at Berkeley

The talk was an in-depth examination of virology, the novel coronavirus’ origins, the prospects for developing an effective vaccine and other topics.

Britt Glaunsinger, a professor in the Department of Plant and Microbial Biology, discussed how such viruses are far less rare in the environment than commonly understood and that opportunities for the spillover of viruses from animals to humans are widespread — and increasingly common — and include the recent outbreaks of SARS and MERS. 

For every virus, such as HIV or COVID-19, that succeeds to infect human populations, there are potentially thousands, hundreds of thousands or even millions of interactions that fail to do so, she said, adding, “It is not surprising that we would see more of these spillover events.” 

Cara Brook, a postdoctoral Miller Research Fellow in the Department of Integrative Biology, specializes in zoonotic viruses in bats. Brook explained why many zoonotic viruses are associated with bats, in particular. 

Viruses that evolved in animals that are more closely related to humans are more likely to spread as pathogens in humans. Noting that zoonotic diseases from bats tend to be more virulent in humans than in other mammals, Brooks explained how the bat has unique physiology and metabolic processes, since it is the only mammal capable of sustained, self-powered flight. 

While the idea is still theoretical, bats’ unique physiology could mean they’ve evolved a higher tolerance to viral infections. 

“What we see when that virus crosses into a host that is a nonflying mammal that lacks these unique adaptations is that it tends to cause an extraordinary amount of pathology,” said Brook.

When different types of animals are held together in high stress situations, such as at wildlife markets, it poses a risk for viral spread and mixing. 

“We humans are interfacing more and more with animal populations — not just from wild animal markets or things like that, but from deforestation and forcing animals into higher stress situations where they’re going to come into more contact with humans,” said Glaunsinger. 

Glaunsinger explained how different viruses can mix in animals, creating new types of viruses. For example, she noted that pigs tend to be animals in which avian influenza mixes.

“If those new viruses have just that right combination of features to infect us, then we’re in trouble, at that point,” said Glaunsinger. “Those new viruses are things that our immune systems have never before been exposed to, and this is when the risk for pandemic arises.”

The outbreak has raised questions about whether wet markets — markets that sell fresh meat, fish, produce and other perishable goods — should be regulated or closed. Brook acknowledged that, while such settings can contribute to the spread of viruses, many communities where she has done research have little choice but to eat wildlife. 

“It’s hard to make an argument to quit eating wildlife when you don’t offer any alternative,” said Brook. “I think we need to have a really nuanced approach to this where, if this is a subsistence environment, we need to be offering a viable domestic alternative of protein sources.”

When it comes to developing a vaccine for the novel coronavirus, Glaunsinger explained in detail how vaccines get our bodies to develop antibodies. She noted that the commonly-cited turnaround of 12 to 18 months is aspirational, even given the extraordinary pressure to generate a vaccine. 

But even though vaccines generally take years, she saw reason to hope that this vaccine could be developed much more quickly than normal and discussed the six different strategies that scientists are pursuing — a mix of known and novel strategies. 

“The hope is to find ways to generate long-lasting immunity,” she said. Whether or not the natural infection would eventually generate long-lasting immunity, or whether a vaccine could create it, is still uncertain.

Brook noted that development of the vaccine isn’t necessarily going to translate to its widespread implementation. 

“In addition to creating a functioning vaccine, production and distribution are going to need to occur at unprecedented levels and rates,” she said. “I think it’s going to be longer than that before a majority of people are actually obtaining that vaccine, even after it’s in production.”

Berkeley Conversations: COVID-19 is a live, online series featuring faculty experts from across the Berkeley campus who are sharing what they know, and what they are learning, about the pandemic. All conversations are recorded and available for viewing at any time on the Berkeley Conversations website.