next up in viral epidemics

4-20  

Professor Li Lanjuan and her colleagues from Zhejiang University found within a small pool of patients many mutations not previously reported.  These mutations included changes so rare that scientists had never considered they might occur.

They also confirmed for the first time with laboratory evidence that certain mutations could create strains deadlier than others.  https://www.scmp.com/news/china/science/article/3080771/coronavirus-mutations-affect-deadliness-strains-chinese-study

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10-24-2017    H7N9 influenza viruses that emerged in 2013 in

China had caused severe human infections and deaths.  However,these viruses were nonlethal in poultry.  It is unknown whether H7N9 viruses can acquire additional mutations during their circulation in nature and become lethal to poultry and more dangerous for humans.  Here we evaluated the evolution of H7N9 viruses isolated from avian species between 2013 and 2017 in China and found 23 different genotypes, 7 of which were detectedonly in ducks and were genetically distinct from the other 16 genotypes that evolved from the 2013 H7N9 viruses.  Importantly, some H7N9 viruses obtained an insertion of four amino acids in their hemagglutinin (HA) cleavage site and were lethal in chickens.   

  The index strain was not lethal in mice or ferrets but readily

obtained the 627K or 701N mutation in its PB2 segment upon

replication in ferrets, causing it to become highly lethal in mice and

ferrets and to be transmitted efficiently in ferrets by respiratory

droplet.  H7N9 viruses bearing the HA insertion and PB2 627K

mutation have been detected in humans in China.  Our study

indicates that the new H7N9 mutants are lethal to chickens and

pose an increased threat to human health….

  Several studies have indicated that the H5N1 influenza viruses will

become transmissible in mammals if they acquire more mutations

in their HA protein that allow them to recognize human-type

receptors and the mutation of lysine (K) at position 627 of their

PB26,7,8, or if they reassort with human influenza viruses9.

H7N9 subtype viruses have caused severe human infections and deaths every year in China since they emerged in 201310….

  Indeed the human H7N9 viruses are transmissible in ferrets, although their transmissibility varies among different strains16,17,28,29,30. The ability to bind to human-type receptors and transmit in mammals is an important indicator of the pandemic potential of the H7N9 viruses.  However because the H7N9 viruses showed low pathogenicity in poultry, strategies to eradicate them in poultry have not been successful in China, with the exception of the temporary closure of live poultry markets in cities where human cases were detected.    -Jianzhong Shi et alia  https://www.nature.com/articles/cr2017129

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