Plague, the disease caused by the bacteria Yersinia pestis (Y pestis), has
had a profound impact on human history. In AD 541, the first great plague
pandemic began in Egypt and swept over the world in the next four years.
Population losses attributable to plague during those years were between 50
and 60 percent. In 1346, the second plague pandemic, also known as the Black
Death or the Great Pestilence, erupted and within 5 years had ravaged the
Middle East and killed more than 13 million in China and 20-30 million in
Europe, one third of the European population.
Advances in living conditions, public health and antibiotic therapy make
such natural pandemics improbable, but plague outbreaks following an attack
with a biological weapon do pose a serious threat.
Plague is one of very few diseases that can create widespread panic
following the discovery of even a small number of cases. This was apparent
in Surat, India, in 1994, when an estimated 500,000 persons fled the city in
fear of a plague epidemic.
In the 1950s and 1960s, the U.S. and Soviet biological weapons programs
developed techniques to directly aerosolize plague particles, a technique
that leads to pneumonic plague, an otherwise uncommon, highly lethal and
potentially contagious form of plague. A modern attack would most probably
occur via aerosol dissemination of Y pestis, and the ensuing outbreak would
be almost entirely pneumonic plague.
More than 10 institutes and thousands of scientists were reported to have
worked with plague in the former Soviet Union.
Given the availability of Y pestis in microbe banks around the world,
reports that techniques for mass production and aerosol dissemination of
plague have been developed, the high fatality rate in untreated cases and
the potential for secondary spread, a biological attack with plague is a
serious concern.
An understanding of the epidemiology, clinical presentation and the
recommended medical and public health response following a biological attack
with plague could substantially decrease the morbidity and mortality of such
an event.
A plague outbreak developing after the use of a biological weapon would
follow a very different epidemiologic pattern than a naturally occurring
plague epidemic.
The size of a pneumonic plague epidemic following an aerosol attack would
depend on a number of factors, including the amount of agent used, the
meteorological conditions and methods of aerosolization and dissemination.
A group of initial pneumonic cases would appear in about 1-2 days following
the aerosol cloud exposure, with many people dying quickly after symptom
onset. Human experience and animal studies suggest that the incubation
period in this setting is 1 to 6 days.
A 1970 World Health Organization assessment asserted that, in a worst case
scenario, a dissemination of 50 kg of Y pestis in an aerosol cloud over a
city of 5 million might result in 150,000 cases of pneumonic plague,
80,000-100,000 of which would require hospitalization, and 36,000 of which
would be expected to die.
There are no effective environmental warning systems to detect an aerosol
cloud of plague bacilli, and there are no widely available rapid, diagnostic
tests of utility. The first sign of a bioterrorist attack with plague would
most likely be a sudden outbreak of patients presenting with severe
symptoms.
A U.S. licensed vaccine exists and in a pre-exposure setting appears to have
some efficacy in preventing or ameliorating bubonic disease. The mortality
of untreated pneumonic plague approaches 100%.
Research and development efforts for a vaccine that protects against
inhalationally acquired pneumonic plague are ongoing. A number of promising
antibiotics and intervention strategies in the treatment and prevention of
plague infection have yet to be fully explored experimentally.
Given that naturally occurring antibiotic resistance is rare and the lack of
confirmation of engineered antibiotic resistance, the Working Group believes
initial treatment recommendations should be based on known drug efficacy,
drug availability and ease of administration.
People with household or face-to-face contacts with known pneumonic cases
should immediately initiate antibiotic prophylaxis and, if exposure is
ongoing, should continue it for 7 days following the last exposure.
In addition to antibiotic prophylaxis, people with established ongoing
exposure to a patient with pneumonic plague should wear simple masks and
should have patients do the same.
----- Original Message -----
From: "Michael M. Butler" <butler@comp-lib.org>
To: "Dan Niemi" <Dan459@aol.com>
Sent: Wednesday, October 03, 2001 8:32 PM
Subject: [Fwd: Bubonic Plague]
> Hoo boy. Not sure where this is from, but interesting if true.
>
> Bubonic plague genome is "unusually fluid"
>
> 19:00 03 October 01
> Debora MacKenzie
>
> Bubonic plague, the bacterium blamed for the Black Death of medieval
> Europe and now a potential biological weapon, has had its entire
> genome sequenced. The genes seem to be "unusually fluid", readily
> re-arranging themselves and picking up new genes from other microbes.
>
> That could mean that more virulent strains of plague might emerge.
> More ominously, it suggests that enhanced strains might be relatively
> easy to develop as weapons.
>
> The bacillus that causes bubonic plague, Yersinia pestis, commonly
> infects rodents in Asia, Africa and the Americas. But it occasionally
> spreads to humans, with lethal effect.
>
> It does so by infecting both insects and mammals. Fleas that feed on
> infected rodents swallow the bacteria, which infect and block their
> midguts. The starving fleas feed voraciously, but only regurgitate
> the blood they try to swallow - along with the bacteria. So plague
> spreads among rodents, often causing only mild disease.
>
> If the infected flea bites a human, however, up to half the victims
> die, unless treated with antibiotics. If the bacteria invade the
> lungs of such patients, and they cough them out, nearby people may
> catch "pneumonic" plague. This is always fatal without treatment.
>
> Pneumonic plague is the form feared as a potential biological weapon,
> as it can be released as an aerosol and can spread directly among
> humans, without the intervention of fleas. The Soviet Union developed
> such a plague weapon.
>
>
> "Pathogenicity islands"
>
>
> The gene sequence of Yersinia pestis, produced by Julian Parkhill of
> the Sanger Centre in Cambridge, UK and colleagues, shows how the
> bacillus learned to infect both insects and mammals.
>
> It picked up genes directly from baculoviruses that infect insects,
> including one for a toxin that damages the midgut. It also acquired
> "pathogenicity islands", assemblages of genes from other bacteria
> that help cause human disease.
>
> The sequence also reveals novel surface molecules, which might
> provide new ways to attack plague. But "this genome displays unusual
> fluidity," comment Stewart Cole and Carmen Buchreiser in Nature,
> where the genome is published. Numerous Yersinia genes have been
> copied backwards and have swapped positions within the genome,
> sometimes creating different variants in the same population.
>
> These recombinations could mean differences in virulence in a single
> batch of plague, they note. That could also mean that the bacteria -
> or bioweapons developers - have the genes at their disposal for new
> and potentially nastier strains of disease.
> a
>
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