Dr Deborah Birx warned that the United States could have its own home-grown mutant strain of COVID-19, in the same way that Britain does, because the virus is spreading so fast.
Birx, who announced before Christmas that she would retire when Joe Biden takes office, after being left red-faced for ignoring COVID guidelines during the holidays, made the analysis during a recent meeting of the White House coronavirus taskforce.
She presented a series of graphs and charts, officials have said, which showed a serious spike in cases.
Birx speculated that this could be because a new, more infectious variant of the virus is circulating – in the same way that Britain has been shaken by the new B.1.1.7 strain.
Dr Deborah Birx speculated that a new, home-grown variant of COVID-19 could be circulating
Birx, pictured in March, circulated new charts at a recent taskforce meeting to make her point
Her concerns made it on to the weekly report sent to state governors, which was leaked on Friday.
‘This fall/winter surge has been at nearly twice the rate of rise of cases as the spring and summer surges,’ the report stated.
‘This acceleration suggests there may be a USA variant that has evolved here, in addition to the UK variant that is already spreading in our communities and may be 50% more transmissible.
‘Aggressive mitigation must be used to match a more aggressive virus.’
Birx’s assessment was discounted by the Centers for Disease Control and Prevention (CDC), which attempted in vain to get her views removed from the report, The New York Times reported.
‘Researchers at the Centers for Disease Control and Prevention are monitoring all emerging variants of the coronavirus, including in 5,700 samples collected in November and December,’ said Jason McDonald, a spokesman for the agency.
‘To date, neither researchers nor analysts at C.D.C. have seen the emergence of a particular variant in the United States.’
Birx has not commented publicly on the leaked report.
The mutant strain first identified in the UK, B.1.1.7, was confirmed as having arrived in the United States on December 29, when a member of the National Guard in Colorado working at a nursing home was found with the new strain.
Since then it has been spotted in a handful of states – among them New York, Florida and California – but the CDC estimates that it accounts for less than 0.5 per cent of cases in the country so far.
Researchers have watched SARS-CoV-2 evolve in real time more closely than any other virus in history.
California has had so many cases that patients are treated in parking lots (seen January 3)
The vaccination program has begun, but it is yet to make a dent on the surge in cases
The United States is currently seeing more cases of COVID now than ever before
So far, it has accumulated mutations at a rate of about one to two changes per month. That means many of the genomes sequenced today differ at about 20 points from the earliest genomes sequenced in China in January, but many variants with fewer changes are also circulating.
Many mutations are described as being ‘silent’ because they do not change the structure of the proteins they encode, and produce a three-letter codon that translates to the same amino acid. These mutations are known as ‘synonymous’.
Other mutations may change the codon in a way that leads to an amino acid change, and these are known as ‘non-synonymous’ mutations, but this amino acid substitution does not impact the protein’s function.
Another variant circulating at low levels in the U.S., known as B 1.346, contains a deletion that may weaken vaccines’ potency.
‘But I have seen nothing on increased transmission,’ said Michael Worobey, an evolutionary biologist at the University of Arizona who discovered that variant.
The strain, B.1.1.7, is thought to be 70 per cent more infectious.
It is not believed that B.1.1.7 leads to more severe cases, and higher mortality rates have not been reported.
‘At this time, there is no evidence that this variant causes more severe illness or increased risk of death,’ the CDC stated on their website.
The data suggests that the variant may have already been present in the U.S. at undetectable levels in recent months, since perhaps as long ago as October.
What is the ‘mutant COVID strain’ and why are experts concerned?
Coronaviruses mutate regularly, acquiring about one new mutation in their genome every two weeks.
Most mutations do not significantly change the way the virus acts.
This super strain, named B.1.1.7, was first identified in the UK in November.
It has since been found in France, Spain, Italy, Iceland, Japan, Singapore, Australia and now the United States.
The new COVID-19 variant has a mutation in the receptor binding domain (RBD) of the spike protein at position 501, where amino acid asparagine (N) has been replaced with tyrosine (Y).
It is more infectious than previous strains and potentially more harmful to children.
It is not, however, believed to be any more lethal.
Public Health England researchers compared 1,769 people infected with the new variant, with 1,769 who had one of the earlier strains of the virus.
Forty-two people in the group were admitted to hospital, of whom 16 had the new variant and 26 the wild type.
Twelve of the variant cases and 10 of the ‘older’ virus cases died within four weeks of testing.
Neither the hospitalization nor the mortality differences were statistically significant.