This episode of This Week in Virology (TWiV 1223) covers a range of critical topics in virology and public health. The hosts dissect RFK Jr.'s "Make America Healthy Again" report, exposing its reliance on non-existent literature citations. They then delve into an emerging fungal threat to North American bats and discuss extensive surveillance efforts for avian influenza viruses using bird guano in remote regions of the Global South, highlighting H5N1 dominance, migratory pathways, and the impact of ecological changes and conflicts. Finally, the episode explores research identifying ACE2 from Pipistrellus abramus (Japanese house bats) as the receptor for HKU5 coronaviruses, emphasizing the importance of understanding bat-human interfaces for zoonotic spillover.
Summarizing TWiV 1223: Navigating Misinformation, Zoonotic Threats, and Global Surveillance
0:00 Introduction & MicrobeTV Support: The hosts, Vincent Racaniello, Kathy Spindler, and Brianne Barker, introduce the episode and emphasize MicrobeTV's commitment to providing science and truth, soliciting listener support.
2:34 ASV 2025 Conference Update: Details for the upcoming American Society for Virology meeting in Montreal (July 14-17, 2025), including changes to the schedule (satellites in mornings, reception after lunch, plenaries on first day) and extended residence hall reservation deadlines.
5:23 RFK Jr.'s "Make America Healthy Again" Report: Discussion on the report, which was found to include non-existent citations, downplayed by his press secretary as "formatting issues." The hosts criticize RFK Jr.'s unverified claims, such as the NIH starting its own journal.
7:53 New Fungus Threatening North American Bats: A New York Times article highlights a new fungal species that could further devastate North American bat populations, building on the existing white-nose disease caused by Pseudogymnoascus destructans.
9:37 Avian Influenza Surveillance via Bird Guano (Paper 1):
Purpose: Addresses the scarcity of avian influenza surveillance in low- and middle-income countries where zoonotic crossover is a concern.
Methodology: Over 27,000 fresh bird guano samples collected from remote, uninhabited regions in 10 countries (e.g., Indonesia, Madagascar, Maldives, Papua New Guinea, Somalia) between Dec 2021 and Feb 2023.
Key Findings:
1.33% of samples contained viral RNA.
Significant geographic and spatiotemporal variations in positivity rates (e.g., highest in Eastern Africa/Arabian Peninsula).
H5N1 was the most prevalent subtype, dominant across multiple regions, with phylogenetic clustering aligning with major bird migration flyways.
Samples showed a close relationship to H5N1 viruses currently circulating in dairy cattle.
Detection of HPAI sequences in regions with no reported disease suggests surveillance gaps.
Some H5N1 samples possessed a neurominidase mutation (H275Y) associated with Tamiflu resistance, originating in wild birds never exposed to the drug.
Discussion & Takeaways:
High subtype diversity in some regions (e.g., Papua New Guinea) suggests heterogeneous host populations, increasing reassortment risk.
Specific bird species (waterfowl, sandpipers, gulls, egrets, birds of prey, urban crows/sparrows) and their behaviors (mixing with domestic poultry, scavenging) are key transmission drivers.
Biphasic seasonal patterns of RNA levels (April-June, Dec-Feb) are driven by ecological factors like rainfall and bird congregation, requiring adapted surveillance strategies.
RNA peaks occurred before the widespread 2023 surge in avian influenza, emphasizing the value of early surveillance.
Ecological changes (mining, logging pushing human settlements into wild habitats) and conflicts (displaced populations, unregulated trade) exacerbate zoonotic risk.
The study highlights global inequities in disease surveillance and the necessity for continuous monitoring in dynamic, often underserved, areas.
40:48 ACE2 as Receptor for HKU5 Coronaviruses (Paper 2):
Background: Research on MERBco viruses (MERS-CoV related), many of which are only known from sequences. MERS-CoV uses DPP4, but some MERBco viruses use ACE2.
Methodology: Developed a "MERBco-type" pseudotype assay using a VSV backbone with MERBco virus spike receptor-binding domains (RBDs) to test receptor usage.
Key Finding: A specific clade of MERBco viruses, including HKU5 coronaviruses, uses ACE2 from Pipistrellus abramus (Japanese house bats) as its entry receptor.
Zoonotic Risk:P. abramus bats are "synanthropic" (living in close proximity to human dwellings and modified environments), increasing opportunities for human exposure.
Confirmation: An infectious clone of HKU5 was synthetically created, confirming its use of P. abramus ACE2 in various cell lines, reinforcing the finding.
Structural Insights: AlphaFold3 predicted RBD-ACE2 interactions, and cryo-EM showed the HKU5 spike trimer in a "down" (closed) configuration, potentially linked to its presumed gastrointestinal tropism in bats.
Implications: While HKU5 currently has low affinity for human ACE2, its ability to adapt and the constant human-bat contact in Asia underscore the need for continued surveillance and reduced contact.
1:24:33 Listener Emails:
Correction on Wendy Carlos's "Switched on Bach" availability.
Measles vaccine data to counter misinformation (Bill).
Listener's experience being mistaken for a medical professional due to TWiV knowledge (Jason).
1935 article on science's vital role in the world (Jay).
Thoughts on public opinion based on belief vs. evidence, and links to research on T-cells in the brain (Blue Pilgrim).
Global health essays and congratulations to a graduating resident (Jinx).
Concern over federal cuts impacting Rocky Mountain Labs (Heidi).
A humorous cartoon about grammatical voices in scientific writing (Glenner).
A detailed letter proposing a tax on high incomes in Democratic-led states to backfill NIH funding cuts (Brian).
1:39:39 Weekly Picks:
Brianne: A newly discovered non-coding genetic mutation in orange cats that blocks black pigment production.
Kathy: A middle schooler's STEM project that led to the discovery of a bacterium with antibiotic activity and an anti-cancer compound from goose poop.
Vincent: An opinion piece titled "Elon Musk’s Legacy Is Disease, Starvation and Death," criticizing the impact of USAID funding cuts on global health.
David (Listener): Carl Sagan's "The Demon-Haunted World: Science as a Candle in the Dark" and a hypothetical question about international medical care access for US citizens if vaccine/medical access is removed domestically.