article review: "a new look at an old virus: patterns of mutation accumulation in the human...
Post on 26-Jul-2015
84 Views
Preview:
TRANSCRIPT
A new look at an old virus:
patterns of mutation
accumulation in the human H1N1
influenza virus
since 1918
Robert W. Carterand John C. Sanford (2012)
1889-
1890
1893 1917-1918 1957 1977 2009
~375
mutations
H1N1
influenza
strain
entered
human
population H1N1
“Russian”
flu
outbreak
Derivatives
of original
virus
circulating
in human
and swine
Human
strain went
extinct
Reappeared in
Anshan, China
Swine
H1N1
Reassortment
between
H1N1 and
H1N2
“We are now moving into the post-
pandemic period. The new H1N1
virus has largely run its course.”
Dr. Margaret Chan
WHO Director-General
10 August 2010
• Process virus changes to
become harmless or less
virulent
• Long term – gradually through
mutation accumulation
Terminology
Terminology
Influenza virus have high mutation rates
Mutations primarily non-adaptive
( high error rate)
Accumulation of
deleterious mutations
What causes REDUCTION in
mortality rate???
Herd immunity ??
Advances in
medicine & hygiene
??
Natural attenuation of
H1N1 viruses ??
Advances of medicine and hygiene??
Reduction of
mortality rate
and stage of
medical advance
or hygiene
advance is not
synchronic.
Improved herd immunity??
Not sufficient to explain the
continuous decline of H1N1 related
mortality rate over multiple human
generation.
Natural attenuation of H1N1
viruses ??
Found strong correlation
between time, mutation count
and reduced death rate of
influenza H1N1.
Long term historical
evidence and theoretical
studies using numerical
simulation strongly support
the concept of natural
genetic attenuation of
RNA viruses.
Proof of occurrence of
genetic attenuation of H1N1
human lineage?
Almost all human H1N1 influenza lineages rapidly
go extinct.
H1N1 genome is found to be systemically
degenerating since 1918.
Consistent loss of codon specificity overtime
within human H1N1 lineage.
Extinction of human H1N1 lineage both in
1950s and 2009.
“We show compelling new evidence
supporting the extinction of human H1N1 in the 1950s, ……, and an apparent second
extinction event of the human H1N1 lineage in 2009.”
According to author:
REALLY…….?
top related