This Week in Virology TWiV 1305: Lab leak idea called on the carpet
Mar 15, 2026
They cover a newly described Sunshine virus infecting carpet pythons and experiments that trace infection, pathology, and transmission. They explain a genomic method to tell natural spillovers from lab passage and apply it to influenza, Ebola, coronaviruses, and SARS‑CoV‑2. Discussion touches on lab‑passage signatures, historical controls, and implications for interpreting outbreak origins.
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Experimental Infection Confirms Sunshine Virus Causes Python Disease
- Sunshine virus infects Australian carpet pythons and belongs to Sunviridae, a mononegavirales negative-strand RNA family grown in viper heart cells at 30°C.
- Researchers fulfilled Koch's postulates by experimental intratracheal/intracoelomic inoculation and PCR/isolation showing persistent infection.
PCR Positivity Precedes Months-Long Clinical Signs In Snakes
- After inoculation pythons become PCR-positive within 4–14 days but clinical neurological signs emerge months later, complicating quarantine decisions.
- Cohousing transmitted infection slowly (114 days for one contact), implying contact transmission, not airborne spread in cages.
Zoonotic Viruses Usually Enter Humans Ready To Go
- Viruses often don't need pre-adaptation in their animal hosts to infect humans according to comparative dN/dS analyses.
- Wertheim et al. used RELAX/K metrics across multiple outbreaks (influenza, Ebola, Marburg, mpox, coronaviruses) to show selection intensifies only after human emergence.
