Why are superviruses rare? | Vincent Racaniello and Lex Fridman

TL;DR

Highly transmissible viruses tend to be less lethal, as lethal viruses have difficulty spreading efficiently. This is due to the selection pressure for viruses to find new hosts and the limitations on transmission when infected individuals are severely ill.

Transcript

there's these deadly viruses they're not very transmissible ebola rabies and then there's these less deadly viruses that are very transmissible um like uh like covid is i guess kind of borderline but uh why isn't there super transmissible super deadly viruses i think if you compare stars one and two you get somewhat of an answer right sars one was ... Read More

Key Insights

• 😣 Highly transmissible viruses like COVID-19 prioritize spreading efficiently over causing severe illness, as this increases their chances of finding new hosts.
• 😜 Limitations on transmission occur when infected individuals are severely ill, leading to reduced opportunities for spreading the virus.
• ❓ Transmission is a powerful selection force for viruses, favoring mutations that enhance transmissibility.
• 😣 Highly lethal viruses like Ebola are not efficient transmitters due to the severe symptoms and limited mobility experienced by infected individuals.
• 🐰 The mixoma virus in rabbits provides evidence of how a highly lethal virus can evolve to become less lethal and more transmissible over time.
• 🥺 Human activities and population growth have facilitated the spread of viruses, leading to the emergence of new and dangerous infections.
• 👻 Studying and understanding highly lethal viruses has allowed scientists to develop effective treatments and vaccines to combat viral diseases.

Questions & Answers

Q: Why aren't there super transmissible super deadly viruses?

Super transmissible super deadly viruses are unlikely to emerge due to the limitations of transmission when infected individuals are severely ill. Highly lethal viruses like Ebola cause severe symptoms that prevent individuals from transmitting the virus effectively.

Q: What role does transmission play in the evolution of viruses?

Transmission is a significant selection pressure for viruses, as they must find new hosts to survive. Viruses that can transmit more efficiently have a higher chance of successful reproduction, leading to increased transmission.

Q: Can a highly lethal virus evolve to become less lethal over time?

Yes, as seen in the case of the mixoma virus in rabbits, highly lethal viruses can evolve to become less lethal and more transmissible. This evolution is driven by the selection pressure for increased transmission, allowing the virus to spread more effectively.

Q: How did human behavior contribute to the increased danger of viruses?

Human behavior, such as congregating in cities, domesticating animals, and global travel, has facilitated the spread of viruses from animals to humans. This increased contact between species has resulted in the emergence of new and dangerous viral infections.

Summary & Key Takeaways

• Highly transmissible viruses like COVID-19 exhibit a significant amount of shedding and transmission before individuals experience symptoms, making them more effective at spreading.

• In contrast, less transmissible viruses like SARS-1 had a lower rate of pre-symptomatic or asymptomatic shedding, making it easier to contain the infection.

• Highly lethal viruses like Ebola have limited transmission opportunities since individuals become too sick to interact with others, reducing the chances of spreading the virus.