Bubonic Plague: An Airborne Toxic Event

by Alena M. James

Yersinia pestisis a gram negative, bacillus shaped bacteria that prefers to reside in an environment lacking oxygen (anaerobic). It is typically an organism that uses the process of fermentation to break down complex organic molecules to metabolize.  However, the organism is commonly referred to as being a facultative anaerobe, because it can live in the presence of oxygen and undergo respiration to generate energy for its cell. Its facultative capability is one reasons the organism can induce infection in highly oxygenated lung tissue.

This organism, primarily a zoonotic pathogen, has been held responsible for causing the bubonic form of plague responsible for the Black Death, the 14th century event that lead to the death of millions of Europeans. For years, the cause of the Black Death Plague pandemic has been linked to fleas. In much of Europe at this time, unsanitary living conditions provided the perfect breeding grounds for flea infested rats to flourish; while the fleas served as the perfect arthropod vector for Y. pestis to flourish.

The route of transmission of Y.pestis, from fleas to humans, was thought to occur via the urban cycle—when an urban rat becomes infected with fleas from a wild animal. Crowding in cities, poor hygiene, and unsanitary living conditions attracts large rat populations to the area. When a flea carrying Y.pestis bites a rat, the rat becomes sick and dies. No longer able to parasitize the rat, the flea moves from the rat to a new host. In crowded cities, the fleas from the dead rat will jump to humans to feed. When the flea bites the human it releases Y. pestis into the human’s cardiovascular system. Once in the cardiovascular system, the bacterial organism makes its way to the lymph nodes.  There it replicates and spreads throughout the body causing septicemia. As Y. pestis proliferates within the lymph nodes it also forms hemorrhagic necrosis throughout the body.  Painful swelling arises and the definitive painful symptom, the bubo,appears.  After infection, a patient develops a high fever and the organism can target specific organs of the body like the lungs, liver, and spleen. Without treatment, a patient has a 75% mortality rate.

Last week, British scientists performed comparative DNA analysis on bacterial samples collected from 25 excavated skeletons found in the Clerkenwell area of London. These remains dating back to the 14th century contained samples of Yersinia pestis, the bacteria responsible for the Black Death. In an attempt to evaluate the virulent nature of the pathogen, the Y. pestis DNA collected from these remains were compared to DNA from the Y. pestis responsible for the deaths of more than 30 people in Madagascar back in December 2013. Researchers concluded that the DNA of both organisms revealed a high percentage of similarity and that the pathogenic nature of the 14th century Y. pestis is no more powerful than the Y.pestsis responsible for the Madagascar killings.

After considering this information and examining the plausible death of the skeletons, scientists believe that the fast-acting killing capabilities of Y.pestis are only likely to take place through airborne transmission. This conclusion undermines the urban cycle transmission method and suggests that the Black Death was mostly caused by pneumonic plague and not bubonic. British scientists are determined to examine more modern cases to confirm this new hypothesis. If confirmed, we may see pneumonic plague identified as the causative agent for the 14th century plague pandemic thus altering our historical account of the Black Death.

For British scientists, the transmission of Y. pestsis through respiratory droplets is a much more likely scenario for achieving rapid kills versus the urban cycle transmission method. Bubonic plague is not infectious and there is no human to human transmission from the buboes that form.  However, pneumonic plague can be caused by bubonic plague if the Y. pestis pathogen makes its way via the lymph nodes to the lungs inducing infection. While in the lungs, the organisms are caught in respiratory droplets and are then disseminated into the air when an infected person sneezes or coughs. This quickly makes the host very infectious and a threat to those not yet infected.  The mortality rate for patients suffering from pneumonic plaque without treatment is 100%.


Image Credit: crossrail.co.uk

The Pandora Report 12.20.13

Highlights include more pneumonic plague in Madagascar, H1N1  in Texas, Chikungunya in the Caribbean, H7N9 in Hong Kong, and MERS in Saudi Arabia. Happy Friday, and a very happy holiday season to everyone.

Pneumonic Plague Cases Up in Madagascar
The latest numbers in the plague outbreak in Madagascar suggest as many as  17 of 43 cases may be pneumonic plague – the highly virulent, highly infectious, transmissible person-to-person form of the traditional bacteria. As we’ve mentioned before, the case fatality rate for pneumonic plague is 100% unless antibiotics are prescribed in the first 24 hours following infection. However, as the disease’s incubation period can be up to three days, and as it often presents initially with flu-like symptoms, timely detection can be very challenging. We’ll keep you posted.

Madagascar-Tribune (originally in French) – ” 43 suspected cases of pneumonic plague and bubonic plague were detected Mandritsara since 20 November until 5 December 2013. 17 suspected cases of pneumonic plague were detected Analanjirofo. 15 cases of bubonic plague have been recorded in the district of Ikongo. In the district of Tsiroanomandidy, 3 cases of bubonic plague have been suspected.”

Montgomery County, Texas: Mystery Illness Likely H1N1 Virus
A regional hospital in Texas has reported eight cases of an as yet diagnosed illness – of the eight, four patients have subsequently died. One of the remaining four patients has subsequently been diagnosed with H1N1The CDC is working with local health authorities to determine the pathogen in play.

Houston Chronicle – “Recent mystery deaths in Montgomery County could be attributed to the H1N1 virus. Conroe Regional Hospital this month reported eight cases of a mystery illness to the county’s public health department. Two of the patients tested negative for all flu viruses. Nichols-Contella said the 2013 influenza vaccine protects against the H1N1 virus. None of the patients who died had received a flu shot, the release said.”

Chikungunya Outbreak Grows In Caribbean
Chikungunya has struck the sunny Caribbean, with two cases reported to the WHO last week. Since the initial outbreak, a further 10 cases have emerged. Chikungunya is an Alphavirus, and is spread through arthropods, primarily mosquitoes. The outbreak on St. Martin signifies the first time the virus has appeared in the Western hemisphere. There was no international travel in the case histories of the patients involved. Fortunately, very few people understand better than epidemiologists the tendency of infectious diseases to spread with vigor, so surveillance systems are already in place.

NPR – “Except for a small number of imported cases each year, chikungunya has stayed out of the Americas until now. But U.S. health officials have been on the lookout for its arrival. The chikunguyna virus was discovered in 1955 by two scientists in Tanzania. ‘Microbes know no boundaries, and the appearance of chikungunya virus in the Western Hemisphere represents another threat to health security,’ CDC director Dr. Tom Frieden wrote in statement Wednesday. ‘CDC experts have predicted and prepared for its arrival for several years, and there are surveillance systems in place to help us track it.’ With about 9 million Americans traveling to the Caribbean each year, the CDC anticipates chikungunya will be a more frequent visitor to the U.S. in the next few years. One of the mosquitoes that carries the virus — the Asian tiger mosquito — is already a familiar pest in many parts of the U.S. during the summer.”

Two more H7N9 bird flu cases linked to Shenzhen’s Longgang district
Two individuals who lived or worked near the wet markets which tested positive for H7N9 last week have subsequently contracted the virus themselves. The two have been hospitalized and are in critical condition.  Again, the reemergence of the virus is consistent with expected seasonal patterns.

South China Morning Post – “Three patients who have contracted the H7N9 strain of bird flu had visited the Longgang district of Shenzhen, including the latest case announced yesterday, mainland health authorities said. A 38-year-old Shenzhen man was in critical condition after being diagnosed with the deadly strain of the flu, Shenzhen’s centre for disease control and prevention said. The patient is a migrant worker who lives and works in Nanwan Street, in Longgang district, near one of the infected markets where authorities found the H7N9 virus on December 11. A second patient, a 39-year-old man from Dongguan, commuted to the district. The pair follow Tri Mawarti, a domestic helper who was the first person in Hong Kong diagnosed with the virus. She is believed to have handled a live chicken at a flat in Nanwan Street before falling ill.”

WHO: Middle East respiratory syndrome coronavirus (MERS-CoV) – update
A further two cases of MERS-CoV have been confirmed in Saudi Arabia. The two patients are both female, aged 51 and 26 respectively. The former has no know exposure to the virus, whereas the latter had previously been exposed to an infected patient. Globally, there have been 165 cases to date, with 71 deaths.

WHO – “The first case is a 51 year-old female from Saudi Arabia, living in Jawf province with onset of symptoms on 20 November 2013. She has underlying chronic disease and was transferred to Riyadh for treatment in an intensive care unit. She had no reported contact with animals. The epidemiological investigation is ongoing. The second case is a 26 year-old female who is a non-Saudi healthcare worker in Riyadh. She is asymptomatic. She had reported contact with a 37 year-old male laboratory confirmed case that was reported to WHO on 21 November 2013.”

(image: Clavius66/Wikimedia)

Bubonic Plague in Madagascar

In the latest outbreak of bubonic plague in the country, 20 people died from the disease last week in north-western Madagascar. Bubonic plague, caused by the bacteria Yersinia pestis, is endemic to the island nation, and resulted in 60 fatalities last year alone. The island’s prisoners are especially vulnerable, due to pervasive unsanitary conditions enabling a large rat population in local prisons. However, last week’s outbreak occurred in the relatively remote village of Mandritsara. Health authorities are currently investigating the outbreak.

Plague is spread to humans through infected fleas, often from rats. Bubonic plague is something we’ve written about extensively here on the Pandora Report, usually in a historical context. It’s easy to forgot that for many nations, outbreak of the disease remains a very real fear today.

(image: wikimedia commons)

Image of the Week: Y. Pestis

We know we featured a gallery of plague pictures last week, but the one picture we failed to include was of the bacteria itself. Pictured below is the Yersinia pestis, the bacteria which killed millions by causing plague. While today plague in its bubonic form is easily treated, pneumonic plague has a 100% fatality rate unless antibiotics are administered within 24 hours.

(Image credit: NIAID)

New Bio-containment Lab in Kazakhstan

The Defense Threat Reduction Agency (DTRA), working with the Nunn-Lugar Cooperative Threat Reduction Program have helped fund a new, high-security lab in Kazakhstan for the study of dangerous pathogens. The Central Reference Laboratory (CRL), set to open in 2015, will help provide competitive jobs to local scientists, discouraging them from instead selling their skills to the highest bidder. As many of you know, during its height the the Soviet BW program employed approximately 60,000 individuals, of which 10,000 were thought to highly-skilled researchers and scientists. Kazakhstan in particular was a key location for biological weapons facilities.  When the USSR halted all offensive BW in 1992, most of these 10,000 scientists suddenly found themselves unemployed – programs like these have therefore been critical to preventing proliferation of knowledge.

Reminiscent of the former Soviet “plague stations”, the CRL will focus in particular on Yersinia pestis, which is endemic in the area.

Read more on the lab here.

(image credit: William Weih/DTRA)

Image of the Week: Plague

This week’s image shows us everyone’s favorite scourge – plague! Depicted below is Yersinia pestis, the causative agent of plague, sticking to  the spines of a flea. Throughout history, Y. pestis has contributed to some of the most serious pandemics, at one point killing nearly half of Europe’s population. While plague still pops up occasionally (it’s endemic in the prairie dog population of the American Southwest), prompt treatment with antibiotics prevents serious illness. However, in aerosol form, unless antibiotics are administered in the first 24 hours, infection is almost always fatal. This is a big part of why Y.pestis is considered a potential bioterrorist agent.

Image: NIAID
Image: NIAID