Links to an article in Science magazine about modeling disease spread. The authors, from the London School of Hygiene write about the k number, which is as important as the much-discussed R number, as reflects the dispersal of the virus. The lower the k number, the smaller the number of people the virus spreads from. The flu had a k number of 1 but SARS and MERS had a much lower k number reflecting that infection clusters played less of a role in flu. An estimate of the k number of Covid-19 is 0.1, meaning that 10% of the cases lead to about 80% of the spread. Another estimate from this number is that the virus has to be introduced undetected into a new country at least 4 times before it establishes itself. Patients' characteristics also have a role to play in that some patients will shed virus more virus for a longer period time than others.
https://www.nytimes.com/2020/05/27/health/coronavirus-spread-united-states.html
This is a Carl Zimmer article from the NYT about the spread of the coronavirus in US. A computational biologist from Scripps Institute an evolutionary biology from the U of Arizona and a geneticist at Hutchinson, are quoted in the article. A new analysis of the genomes of coronavirus established that the first case, called WA1 and the second case, WA2, different in 2 mutations. It would have been about 6 weeks to accumulate those mutations and it is believed that the virus circulated in Washington for six weeks but it is likely that it would have taken more than six weeks to accumulate 2 mutations since the coronavirus mutates slowly. A computer modeling experiment showed that the WA1 couldn't have seeded the outbreak there. The implication was that the WA2 was introduced in Washington by travelers from China, meaning that the epidemic was set off by the WA2, after Trump's travel ban from China. They went over the Italian outbreak the same way. The implication is that the epidemics were seeded later than previously believed and that there was time to take advantage of the delay before the virus took off by testing and contact tracing.
https://geneticliteracyproject.org/2020/05/29/viewpoint-believing-that-well-have-a-coronavirus-vaccine-anytime-soon-is-naive-at-best/ This is a link to an opinion in the Genetic Literacy Project, written by a senior fellow of the Pacific Research Institute. Operation Warp Speed notwithstanding, it is unlikely that we will have a Covid-19 vaccine inside of a year, or even a year-and-a-half. The history of vaccines describes obtaining pus from smallpox and using it as the inoculum. It’s actually much more complicated as the opinion describes. How much of the vaccine should be in each dose? Does one dose elicit immunity, or do you need two (as is the case for Shingrix)? How well does it work in the elderly, who are highly vulnerable to COVID-19 infection but tend to mount a poor immune response? Does immunity last long enough to make immunizing billions of people worthwhile? A rush to inoculate could produce side effects that could impede progress for years (RSV vaccine, for example).
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