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WHO ADVISORY COMMITTEE ON
VARIOLA VIRUS RESEARCH
REPORT OF THE TWENTY-THIRD MEETING
VIRTUAL MEETING, 3–4 NOVEMBER 2021
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Report on the variola virus collection at the WHO Collaborating Centre
for Smallpox and Other Poxviruses – United States Centers for Disease
Control and Prevention, USA
Dr Victoria Olson shared an update on the variola virus collection at the United States
Centers for Disease Control and Prevention (CDC). On prior inspections, the variola
virus research laboratories at CDC were in compliance with national and international
requirements and with WHO recommendations. The variola virus collection comprised
360 non-identical isolates stored in two long-term repositories.CDC had completed
initial assembly and phylogenetic analysis of all isolates with extracted DNA to date.
Some additional sequencing may be required if there is insufficient coverage for any of
those isolates. Fifteen isolates without good epidemiological information remain to be
sequenced. In April 2021, a failure of one of the long-term repositories had necessitated
movement of the samples to another freezer. The repository freezer had been repaired
and samples had been returned to long-term storage on 2 August 2021. WHO had been
informed in writing to document this movement, which followed established protocols.
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Report on the variola virus collection at the WHO Collaborating Center
for Smallpox and other Poxviruses at the Centers for Disease Control and
Prevention (CDC), Atlanta, GA
Christina Hutson, Todd Smith, Kimberly Wilkins, Yu Li, Hui Zhao, Christine Hughes, Victoria
Olson
WHO Collaborating Center for Smallpox and other Poxvirus Infections, Poxvirus and
Rabies Branch, Centers for Disease Control and Prevention, Atlanta, GA, United States
of America
The World Health Organization (WHO) Collaborating Centre for Smallpox and other
Poxviruses at the Centers for Disease Control and Prevention (CDC) in Atlanta, GA
continues to maintain one of two consolidated, international collections of Variola
virus strains. Most of these viruses were originally isolated on embryonated eggs and
characterized during the final years of the smallpox eradication programme. Currently, the
variola virus collection at CDC comprises 360 non-identical isolates. The virus collection is
maintained in two separate freezers, one of which is a back-up freezer remaining largely
untouched. In the United States of America,Variola virusis a select agent and is subject to
the select agent regulations (42 CFR part 73).
Secure databases addressing WHO recommendations and United States Federal Select
Agent Program requirements have been constructed and maintained to track usage of
variola virus. Enhancing our database of variola virus sequences and in-silico analysis
capabilities will improve our understanding of how to best use medical countermeasures
such as diagnostics and antiviral therapies. Annual reports on the status of these collections
are provided to WHO. No new variola virus seed pools were added to working stocks
between 2020 and 2021.
In 2020, 20 original variola virus specimens were processed and sequenced without
propagation. The compilation of variola virus samples sequenced in previous years has
been completed
In 2021, sample analysis of original isolates removed from the repository freezer in 2020
was conducted. These additional isolates were selected based on historical information
available such as geographic location, date, and epidemiologic data.
Since the twenty-second meeting of the WHO Advisory Committee on Variola Virus
Research held in November 2020, WHO-approved research activities using variola
virus from the repository have focused on: 1) regeneration of non-infectious material for
diagnostic support; 2) evaluation of monoclonal antivirals (monoclonal biologics); and 3)
determining whether humanized mice are a suitable animal model for human smallpox.
The laboratory space was in active use from 24 July 2020 to 12 April 2021. The laboratory
underwent decontamination prior to preventive maintenance in April 2021 and remained
inactive (“cold”) for a period due to the pandemic. The laboratory became active (“hot”)
again on 20 July 2021. During August 2021, the Federal Select Agent Program conducted
an inspection and had no specific recommendations.
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