Can Bats Pass (Corona)viruses to Humans?

Observations & questions arising from a March 2, 2018 research letter

Confession:

I do NOT fully understand what the basis is for believing that coronaviruses can transmit from bats to humans.

Until recently, I hadn’t really thought much about humans catching anything from bats. I’ve essentially ignored the topic because I see no evidence of a spreading risk-additive pathogen circumnavigating the globe in late 2019/early 2020 - whether from a cave, market, laboratory, or anyplace else. Plus, I don’t like bats and would rather not think about them at all.¹

Then I came across March 5, 2018 research letter in Virologica Sinica: Serological Evidence of Bat SARS-Related Coronavirus Infection in Humans, China by Chinese scientists and a few people from EcoHealth Alliance, including Peter Danszak. No doubt the study is already well-known by Real Scientists and those who have followed the SARS-CoV-2 Origin Adventure, but it’s new to me.

Despite virology and serology not being my areas of expertise, I can read pretty well and therefore have observations & questions about what the authors reported. (I will gladly accept correction if I’ve missed something in this study or about the notion of “spillover” from bats to humans.)

Before describing their study, Wang et al say,

“some SARSr-CoVs may have high potential to infect human cells, without the necessity for an intermediate host. However, to date, no evidence of direct transmission of SARSr-CoVs from bats to people has been reported.”²

Remember, this is after the SARS “Pandemic,” which was speculatively-traced to civets and bats.

So, there was no such evidence of direct transmission by 2018, yet research dollars were being spent on virus-hunting in bat caves, because you never know when a bat is going to directly transmit a SARS-CoV to a person and ignite a pandemic? And SARSr-CoVs had been detected in humans and in bats, respectively, so there *must* be a connection?

Anyway…

Wang et al’s study involved serological surveillance of 218 residents of four Chinese rural villages in the same county, close to two caves where researchers had been conducting long-term coronavirus surveillance since 2011. The caves had a lot of rhinolophusspp bats, which they had determined carried a lot of different SARS-CoVs. The area wasn’t involved in the 2002-2003 SARS events and none of the participants were sick with respiratory illness when the samples were taken. As a comparison, the researchers used 240 serum samples from random blood donors in 2015 in Wuhan, far from the caves and where bat-contact was thought to be less likely. None of the donors had a known prior SARS infection or contact with SARS patients.

The testing methods used are beyond the bounds of my knowledge & skills to evaluate robustly, but the central finding was six samples (all from residents in the four villages) being seropositive for SARS antibodies above an established theshhold using a protocol called ELISA.³

Of the six samples

• None reported exposure to SARS-sick people.

• Only two were from people who reported any history of “traveling” from where they live - one to a province 1,000+ km away and the other to the next county 1.4 km away.

• “All had observed bats flying in their villages.” 🦇 (Direct quote)

Because the antibody levels of the six people’s samples were relatively high as compared to levels of patients who had recovered from SARS two to three years later, the researchers concluded that the positive serology obtained in the study might have not have been due to prior infection with SARS-CoV. What the researchers are saying it could be due to if not prior SARS-CoV infection isn’t clear to me. (NL63 reactivity, perhaps - which is mentioned in the results?)

But the strangest conclusion is “Our study provides the first serological evidence of likely human infection by bat SARSr-CoVs or, potentially, related viruses.”

Where did that come from? The fact that “All [seropositive villagers] had observed bats flying in their villages”?

Almost, but not quite. Here’s the leap:

“…considering that these individuals have a high chance of direct exposure to bat secretion in their villages, this study further supports the notion that some bat SARSr-CoVs are able to directly infect humans without intermediate hosts, as suggested by receptor entry and animal infection studies (Menachery et al. 2016).”

How and when did bat secretions enter the study?

And where is the evidence that human contact with bat secretions occurred in any meaningful way, or that such contact transmits coronaviruses?⁴

Naturally, the authors say all of this means more surveillance is needed, which is to say they want more funding:

Our current study suggests that our surveillance is not exhaustive, as one would have expected, and that further, more extensive surveillance in this region is warranted. It might also be prudent to combine serological surveillance with molecular surveillance of bats in future, despite the technological challenges that this represents.

But why? To what end? The samples that tested positive were from people who weren’t even sick, for heaven’s sake!

Not only do the authors admit as much before saying more surveillance is needed, they also refer to the subjects’ infections as bat SARSr-CoV infection.⁵

During questioning, none of the 6 seropositive subjects could recall any clinical symptoms in the past 12 months, suggesting that their bat SARSr-CoV infection either occurred before the time of sampling, or that infections were subclinical or caused only mild symptoms.

This is cause for concern and justification for closer monitoring of coronaviruses in bats because…?

Incredibly, the results from this study appear to be referenced in Danzak’s rejected DEFUSE Proposal (p 2-3), which was submitted only a few weeks after the March 2, 2018 research letter. A direct reference to the research also appears in the February 11, 2020 WHO SituationReport on “Novel Coronavirus” (p. 2).

This isn’t about zoonotic origin versus lab concoction (which is a false and meaningless dichotomy regardless). If transmission of coronaviruses can’t be demonstrated or proven in the natural world - whether from bat to human or human to human - there is simply no way scientists can violate those laws and make the impossible possible through their hubristic tinkering.

It’s more than possible that whatever is being detected in humans and/or bats is related to a response to the environment and/or is shaped by numerous other factors. The mechanisms around the agents or “packets of information”⁶ called viruses aren’t well-understood.

Writing for

PANDA

, Thomas Verduyn put it this way.

Despite all our efforts and research, mankind still knows very little about where viruses come from, how they jump from animals to humans, when they jumped, or what happens when they do. Of all the viruses in existence, few have ever been sequenced. None have been tested for like SARS-CoV-2,  leaving us hopelessly ignorant of what is normal, what is happening, and what existed before 2020. — “Right off the Bat, They Were Lying”⁷

I agree. We don’t know as much as “The Science” would have us believe.

From my non-biologist point of view, the evidence for bats transmitting SARS-CoVs to humans looks thin.

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UPDATES

How about camels? 🐪

h/t

Jennifer Smith, PhD

for sending me this relatively balanced July 3, 2024 article How Studying Bat Viruses Can Help Prevent Zoonotic Disease, published by the American Society of Microbiologists. The underlying, unproven assumption still appears to be that viruses “in” or carried by bats can transmit or “spill over” to humans.

1. My closest encounters have been with the Malayan Flying Fox bats at Disney World’s Animal Kingdom.

2. I am taking them at their word, mostly because it saves me the time of conducting a literature review in an unfamiliar field of study.

3. This is not to minimize the importance/role/impact of the methods on the findings - only to admit my shortcomings with the technical aspects and defer to more-knowledgable readers. I don’t think serology testing and coronaviruses are well-suited to each other. The authors of this particular study, for example, say, “Coronaviruses are known to have a high mutation rate during replication and are prone to recombination if different viruses infect the same individual (Knipe et al. 2013). From our previous studies of bat SARSr-CoVs in the two caves near these villages, we have found genetically highly diverse bat SARSr-CoVs and evidence of frequent coinfection of two or more different SARSr-CoVs in the same bat (Ge et al. 2013).” Such diversity seems to present a challenge to tests seeking to assess seroprevalance, whether in bats or humans.

4. I have a lot of squirrels in my yard. There are white-tailed deer that live in the woods nearby. I see foxes and coyotes on occasion. Blue jays and robins nest in the trees. Hawks fly overhead. To my knowledge, I do not come into regular or significant contact with these creatures’ secretions.

5. At the risk of sounding really stupid, I confess I don’t understand what “infection” means. One source says, “Infection occurs when viruses, bacteria, or other microbes enter your body and begin to multiply.” I understand this idea with bacteria, but do viruses “enter” the body? From where?

6. “Packets of information” is the phrase a New York City doctor we interviewed used when considering what viruses are. I increasingly appreciate that characterization because it resists the question of whether viruses exist and instead invites questions about how what we call viruses are linked to or causal of various illnesses.

7. Similar to questions Verduyn poses elsewhere in his article, we might ask, “Do bats get sick with respiratory illness? Do bats infected with coronaviruses/SARS-CoVs get sick? Are we sure?”