Thread by @DrEricDing

Followup 🧵: the concerning influenza virus dubbed G4- a unique blend of three lineages: one similar to strains in Euro & Asian birds, the H1N1 strain that caused the 2009 pandemic, and N America H1N1 that has genes from avian, human, and pig influenza.
sciencemag.org/news/2020/06/s…

2) “The G4 variant is especially concerning cuz its core is avian influenza virus—to which humans have no immunity—w/ mammalian strains mixed in. “it appears that this is a swine influenza virus that is poised to emerge in humans. Clearly it needs to be monitored very closely.”

3) “G4 virus has shown a sharp increase since 2016, and is the predominant genotype in circulation in pigs detected across at least 10 provinces”

4) “Sun Honglei, the paper’s first author, says G4’s inclusion of genes from the 2009 H1N1 pandemic “may promote the virus adaptation” that leads to human-to-human transmission. Therefore, “It’s necessary to strengthen the surveillance”

5) “Influenza viruses frequently jump from pigs to humans, but most do not then transmit between humans. Two cases of G4 infections of humans have been documented and both were dead-end infections that did not transmit to other people.”

6) “The likelihood that this particular variant is going to cause a pandemic is low,” says Martha Nelson, an evolutionary biologist at the U.S. National Institutes of Health’s Fogarty International Center who studies pig influenza viruses in the US and their spread to humans.”

7) “But Nelson notes that no one knew about the pandemic H1N1 strain, which jumped from pigs to people, until first human cases surfaced in 2009. “Influenza can surprise us,” Nelson says. “And there’s a risk that we neglect influenza & other threats at this time” of COVID-19.”

8) “While Nelson thinks the predominance of G4 in their analysis is an interesting finding, she says it’s hard to know whether its spread is a growing problem, given the relatively small sample size. “You’re really not getting a good snapshot of what is dominant in pigs in China”

9) “In the paper, Sun and colleagues—including George Gao, head of the Chinese Center for Disease Control and Prevention—describe lab dish studies that show how G4s have become adept at infecting and copying themselves in human airway epithelial cells.”

10) “The viruses also readily infected and transmitted between ferrets, a popular animal model used to study human influenza. The researchers found antibodies to the G4 strain in 4.4% of 230 people studied in a household survey—and the rate more than doubled in swine workers.”

11) “Sun says it makes sense to develop a vaccine against G4 for both pigs and humans. Webster says at the very least, the seed stock to make a human vaccine—variants of a strain that grow rapidly in the eggs used to make a flu vaccine—should be produced now.”

12) “Making the seed stock is not a big deal, and we should have it ready,” Webster says.

China rarely uses influenza vaccines in swine. Nelson says U.S. farms commonly do, but the vaccine has little effect because it’s often outdated and doesn’t match circulating strains.”

13) “Ideally, Nelson says, we would produce a human G4 vaccine and have it in the stockpile, but that’s an involved process that requires substantial funding. “We need to be vigilant because viruses have no interest in whether we’re already having another pandemic,” Nelson says.”