Excited to be enrolled in a free @MIT class on coronavirus. Today's lecturer is David Baltimore of MIT and CalTechn. #Follow this thread for live tweets. http://web.mit.edu/webcast/biology/covid-19-sars-cov-2-and-the-pandemic/

LIVE: Nobel Prize winner David Baltimore says, "I have a great love for viruses.... I never imagined that at the end of my career, which is now... a virus would rule the world."

LIVE: David Baltimore says viruses "seem to have evolved fro bits and pieces of the living world."

LIVE: David Baltimore: All organisms use DNA to store their genetic information... except viruses. Some viruses use RNA. "They are tiny objects consisting of a protected nucleic acid core that lack ribosomes... and can replicate themselves only by penetrating living cells."

LIVE: David Baltimore says there's no agreement on whether viruses are alive, since they can't replicate by themselves, unless they invade a living cell and take over its reproductive machinery. Viruses are little bigger than organelles.

LIVE: David Baltimore says there are "an uncountable number of viruses." There are at least 1500 *species* of viruses. "They're all parasites. They all grow only inside living cells."

LIVE: David Baltimore says viruses may have evolved from the "pre-cellular" world, before there were cells. "There are genes with no known relatives, which presumably evolved within the virus itself."

LIVE: David Baltimore, who won Nobel Prize in 1975 for his work on retroviruses, is lecturing online about viruses. Viruses can multiply 100-fold in 20 minutes. "Viruses have to continually find new hosts that haven't experienced the virus."

LIVE: David Baltimore is making it easier for me to transcribe his lecture. Trying to live tweet @DrPaulOffit is much more challenging because he talks too fast.

LIVE: David Baltimore says viruses sometimes jump from one species to another. When they come into the human world, we say they have "emerged." Which means we didn't think about them before.
Slide: "This is what it looks like inside a cell."

LIVE: David Baltimore says "emerging" viruses that jump from wild animals to domesticated animals or humans are the "ones that worry us the most," b/c they often become much more virulent when they find a new host.

LIVE: David Baltmore mentions Schmallenburg virus, which emerged on a farm in 2010 and within a few years had reached 1400 farms before burning itself out.

LIVE: David Baltimore says the viruses we care about the most are HIV and the novel coronavirus, which don't have a vector and are spread from human to human. "Viruses are ubiquitous. There are viruses of all the organisms in the oceans."