This episode of This Week in Virology reviews the passing of molecular biologist James D. Watson, co-discoverer of the structure of DNA. The hosts then delve into a historical 1983 paper from Harald zur Hausen's laboratory, a pivotal study that used early molecular techniques like Southern blotting to identify and differentiate Human Papillomavirus (HPV) types 6 and 11. The research established the prevalence of these specific HPV types in genital and laryngeal papillomas (warts) and found early evidence of their presence in some cervical carcinomas, a key step in proving the viral cause of cervical cancer. The main segment discusses a modern influenza human challenge study where healthy volunteers were infected with H3N2 virus. The study provides a detailed timeline of infection, revealing that viral shedding peaks 3-5 days post-inoculation and begins approximately one day before the onset of major symptoms like runny nose and congestion. Findings suggest that speaking expels more viral RNA than breathing and that environmental contamination is minimal, reinforcing the primary role of respiratory transmission over fomites.
Smelling the Flu: Unpacking HPV History and Influenza Transmission
6:32 The Passing of a Scientific Giant: The episode begins by reporting the death of James D. Watson at the age of 97. The hosts reflect on his monumental contribution as the co-discoverer of the DNA double helix at age 25, while also acknowledging the controversies that marked his later career.
13:16 Bird Flu Surges Amidst Public Health Funding Cuts: Alan Dove reports on a surge of H5N1 avian influenza in US poultry, which is occurring with little CDC monitoring. This is compounded by the US pulling funding from the World Health Organization (WHO), a decision that could jeopardize the ability to accurately select strains for future seasonal flu vaccines.
21:39 The Origins of the HPV-Cancer Link: The hosts discuss a foundational 1983 PNAS paper from Nobel laureate Harald zur Hausen's lab. This research was critical in linking specific HPV types to human diseases before the era of PCR and widespread sequencing.
32:26 Early Molecular Virology: The paper used techniques like Southern blot hybridization to differentiate HPV-6 from a newly identified type, HPV-11, based on how their DNA sequences matched. This method was essential for classifying viruses based on their genetic makeup.
49:48 HPV 6 & 11 Cause Warts: The study demonstrated that HPV types 6 and 11 were the primary causes of benign anogenital and laryngeal warts (papillomas). This finding explains why these two types are included in the modern Gardasil 9 vaccine, not because they are high-risk for cancer, but to prevent the widespread occurrence of warts.
51:57 A Hint of Malignancy: Crucially, the researchers also detected HPV-11 DNA in a few malignant cervical tumors. This provided some of the first direct molecular evidence associating a specific, sexually transmitted papillomavirus with cancer, paving the way for the later discovery of high-risk types like HPV-16 and HPV-18.
56:51 Inside a Controlled Human Influenza Study: The main paper discussion covers a study where eight healthy volunteers were intentionally infected with an H3N2 influenza virus to precisely track the course of infection.
1:08:12 Viral Shedding and Symptoms Timeline: Viral shedding peaked 3 to 5 days after inoculation. Key takeaway: Participants began shedding the virus (detectable by PCR) approximately one day before they started feeling sick with the most common symptoms: runny nose, nasal congestion, and headache.
1:27:47 How Influenza Spreads: The study found that speaking expels significantly more viral RNA than passive breathing. While viral RNA was detected in the air, no infectious virus was recovered from aerosols, likely due to limitations in the collection method. Furthermore, minimal viral RNA was found on surfaces in patients' rooms, suggesting environmental transmission (fomites) is not a major route.
1:33:36 The Shedder Spectrum: Participants were categorized as high, low, or non-shedders. Only the four high-shedders developed a significant antibody response (seroconverted). The two "non-shedders," who never tested positive for the virus despite inoculation, still reported mild symptoms, raising questions about the role of innate immunity in preventing a full-blown infection.