Amazing stuff!
"A group of volunteers spent days locked in a small hotel room with people actively infected with the flu. They played games, shared objects, and exercised together in conditions designed to help the virus spread. Yet not a single person caught influenza.
The unexpected finding comes from a well-designed study that set out to answer a basic question: how does flu really spread? ...
How efficiently the virus spreads depends on several factors, including how much virus an infected person sheds, the temperature and humidity of a room, and how close people are to one another. ...
They brought together groups of participants in a hotel room, mixing people with active influenza infections, referred to as donors, with uninfected volunteers, referred to as recipients. The aim was simple: see whether flu would spread under conditions designed to favour transmission.
Despite prolonged close contact over several days, no recipient became infected. ..."
From the abstract:
"A previous controlled human influenza transmission trial produced minimal transmission using nasal inoculation of an egg adapted virus. Therefore, we implemented a new trial with naturally infected Donors.
We recruited healthy Recipients for four, two-week hotel quarantine cohorts and naturally infected, qRT-PCR confirmed Donors for two cohorts. Five Donors (mean age: 21; 80% female; two H1N1, three H3N2, one for cohort 24b and 4 for 24c, Jan-Feb 2024) exposed Recipients (mean age: 36; 54% female, eight in cohort 24b and 3 in 24c) in a hotel room with limited ventilation but a high air recirculation rate.
We collected exhaled breath, ambient and personal bioaerosols, fomite swabs, and sera, and analyzed samples using dPCR and fluorescent focus assays, hemagglutination inhibition (HAI) assay, and enzyme-linked immunosorbent assay (ELISA). Compared with previously studied community-acquired influenza cases, we detected viral RNA (44%) and culturable virus (6%) less frequently and measured fewer viral RNA copies (79 – 8.9 × 103 copies/30-min) in Donors’ exhaled fine aerosols. One of 23 surface swab samples was culture positive. At admission, 8 of 11 Recipients had HAI titers ≤10 but 9 of 11 had stronger binding antibody responses than Donors against vaccine strains corresponding to Donor viruses.
No Recipient developed influenza-like illness, PCR-positive respiratory samples, or serological evidence of infection.
Potential explanations and insights regarding lack of transmission include importance of cough and seasonal variation in viral aerosol shedding by Donors, of potential cross-reactive immunity in middle-aged Recipients with decades of exposure, and of exposure to concentrated exhaled breath plumes limited by rapid air mixing from environmental controls that distributed aerosols evenly. Future trials over multiple seasons, Donors that cough, younger recipients, and environments that preserve normal exhaled breath plumes will be required to observe transmission from naturally infected Donors under controlled conditions and generate new insights into influenza transmission dynamics."
Credits: The Flyover
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