This episode of "This Week in Virology" (TWIV) explores two significant scientific papers. The first paper details the "reverse zoonosis" of the 2009 H1N1 influenza virus, highlighting how humans frequently transmit the virus to pigs. Pigs then serve as a crucial "mixing vessel" where the virus undergoes genetic and antigenic evolution, potentially developing resistance to human vaccines and posing a future pandemic threat, underscoring the vital need for continued surveillance. The second paper presents compelling evidence from a "natural experiment" in Wales, demonstrating that the herpes zoster (shingles) vaccine significantly reduces the incidence of dementia. This study offers strong, non-correlational data linking herpes virus reactivation to dementia and suggests a simple, actionable intervention. The hosts also discuss podcast sustainability, share a remembrance for colleague Dr. Dixon Despommier, and address listener emails, covering topics like misinformation surrounding poultry flu vaccines, measles transmission, the devastating impact of cuts to global health initiatives, and the broader implications of political interference in science and public health.
This Week in Viology (TWIV) - Episode 1207 Highlights
0:00 Podcast Introduction & Support: Hosts Vincent Drainello, Alan Dove, and Rich Condit introduce TWIV episode 1207. They emphasize listener support as the primary funding source for their ad-free science programs.
2:45 American Society for Virology (ASV) 2025 Meeting: Details are provided for the ASV 2025 meeting in Montreal (July 14-17), including satellite programs, plenary sessions, and deadlines for ASV Cares and early bird registration.
3:39 Tribute to Klaus Conselman: The hosts announce the passing of Klaus Conselman, renowned for establishing the first reverse genetics system for a negative strand RNA virus (rabies) and his contributions to innate immunity and neurotracing. He is remembered as a pivotal mentor and friend.
9:01 Paper 1: Swine Flu Zoonosis and Pandemic Risk:
9:26 Human-to-Swine Spillovers: Research reveals 370 separate instances of human-to-swine H1N1 influenza transmission in the US between 2009 and 2021.
10:51 Swine as a Mixing Vessel: Pigs serve as a significant intermediate host where flu viruses evolve, leading to antigenic changes that could evade current human seasonal vaccines.
11:18 Zoonotic Threat: The persistence of H1N1 in pigs has led to at least five swine-to-human transmission events, highlighting the zoonotic potential of these evolving pig-adapted viruses.
13:15 Historical Context: The 2009 H1N1 pandemic virus re-emerged after evolving in pigs for over 90 years following its human-to-swine transmission in 1918.
16:50 Difficulty of Engineered Pandemics: The vast number of spillovers without major human outbreaks illustrates the immense evolutionary difficulty of creating a virus that can "trash humans," countering notions of easy lab-origin pandemics.
27:40 COVID-19 Impact: The COVID-19 pandemic, with its reduced human activity, led to a sharp decrease in human influenza but sustained high levels of flu in pigs, demonstrating pig-to-pig transmission and long-term viral persistence.
41:11 Natural Experiment Design: A study conducted in Wales exploited a unique shingles vaccine rollout cutoff date (September 2, 1933) to create a quasi-randomized controlled trial, comparing dementia rates in vaccine-eligible vs. ineligible populations.
43:35 Vaccine Efficacy Against Dementia: The study found a significant reduction in both shingles and, notably, dementia diagnoses among the vaccine-eligible group.
47:00 Zostavax vs. Shingrix: The study used the older Zostavax vaccine, raising questions about whether the newer, more effective Shingrix vaccine would yield similar (or even better) results.
1:01:00 Robust Statistical Analysis: Extensive statistical analyses were performed to rule out confounding variables, solidifying the link between shingles vaccination and reduced dementia risk.
1:09:00 Potential Mechanisms: The protective effect is likely due to both a reduction in VZV (herpes virus) reactivation and a broader immunomodulatory effect of the vaccine.
1:11:53 Public Health Implications: This provides strong evidence that a widely available and relatively simple intervention (shingles vaccination) could significantly reduce dementia rates, making it a critical public health strategy.
1:17:08 Listener Emails - Diarrhea & Viral Flushing: A listener suggests that virus-induced diarrhea's second phase might serve to flush newly replicated virus from the GI tract.
1:19:44 Listener Emails - RFK Jr. on Poultry Flu Vaccine: The hosts debunk RFK Jr.'s claims that poultry vaccines create "mutant factories" or that natural infection is preferable, asserting his fundamental misunderstanding of vaccinology and animal husbandry.
1:24:47 Listener Emails - Measles Transmission by Immune Individuals: The hosts clarify that while 100% sterilizing immunity is rare, vaccinated individuals are not efficient transmitters of measles; outbreaks are driven by unvaccinated populations.
1:26:35 Listener Emails - President's Malaria Initiative Cuts: A listener expresses deep concern over the reported ending of the President's Malaria Initiative, attributing it to Elon Musk's influence and forecasting devastating increases in malaria deaths in Africa.
1:32:00 Listener Emails - Political Interference in Science: Emails highlight Trump's executive order on COVID-19 vaccine mandates (seen as political posturing) and the CDC reportedly burying a measles forecast, demonstrating how political agendas threaten public health and scientific communication.
1:34:03 Rich: Shares research on how certain roller coasters may help pass small kidney stones (e.g., Thunder Mountain, with the back car being most effective).
1:39:39 Alan: Recommends digital subscriptions to classic science fiction magazines: "Analog Science Fiction and Fact" and "Azimov Science Fiction."
1:41:09 Vincent: Picks articles advocating for scientists to engage more broadly with the public ("How science under threat in the US" by Ran Blackman) and discussing the intersection of tech, democracy, and science ("Why Tech Dirt is now a democracy blog" by Mike Masnik).