The strain of the virus in the current monkeypox outbreak has far more mutations than would be expected, several that increase transmission

The
study comes from Portugal’s National Institute of Health in Lisbon,
which was the first institution to genetically sequence the current
strain behind more than 3,000 cases of monkeypox in Europe, North
America, and other regions that had never seen the virus until this
year.

Researchers found the current strain diverges from the
original strain by 50 single nucleotide polymorphisms (SNPs), and
several mutations made the virus more transmissible. The strain belongs
to clade 3 of the West African strain of the virus, which is less fatal
than the Congo Basin clade. Monkeypox outbreaks from clade 3 are
typically reported from western Cameroon to Sierra Leone and usually
carry a less than 1% case-fatality rate.

The authors said the
outbreak was likely not caused by undetected silent spread, or from an
animal-to-human crossover event. Instead, “Current data points for a
scenario of more than one introduction from a single origin, with
superspreader event(s) (e.g., saunas used for sexual encounters) and
travel abroad likely triggering the rapid worldwide dissemination.”

The
authors also said the 50 SNPs that diverge from the original strain are
far more (roughly sixfold to 12-fold more) than one would expect
considering previous estimates of the substitution rate for
orthopoxviruses, which typically have 1 to 2 substitutions per site per
year.

Modeling study shows potential growth of outbreak

In another study, this one published today in The Lancet Microbe,
scientists use modeling to predict what will happen in nonendemic
countries if public health measures to curb ongoing outbreaks are not
taken.

They predict that, without interventions, the introduction
of 3 cases in a country could cause 18 secondary cases, 30 could cause
118 secondary cases, and 300 cases could cause 402 secondary cases.

Contact
tracing and surveillance, isolation of symptomatic cases, and ring
vaccination would reduce the number of secondary cases by up to 86.1%
and the duration of the outbreak by up to 75.7%, the authors conclude.

The
authors also said the outbreak is a moderate international concern.
Currently, consultants to the World Health Organization are weighing if
the outbreak constitutes an international public health emergency during
a 2-day meeting.

US, Portugal add more cases

In the United States, the Centers for Disease Control and Prevention said the national total is now 173 in 24 states, an increase of 17 cases since yesterday.

A New York City
sexual health clinic offering monkeypox vaccine to men who have sex
with men was forced to close because of overwhelming demand. Many men
sought the vaccine in the days leading up to Pride celebrations.

Portugal
now has 348 monkeypox cases, with 20 new cases in the last 24 hours.
Along with Spain and the United Kingdom, Portugal has the most cases in
Europe.

In other news, Croatia and Taiwan each reported their first cases of the virus.