A case of bubonic plague, responsible for the Black Death, has been detected in a human in the US state of Colorado.
Health officials are urging people to seek medical attention if they have symptoms of the disease that killed up to 50 million people from 1346 to 1353.
‘We advise all individuals to protect themselves and their pets from plague’, said Alicia Solis, from the Pueblo County’s Office of Communicable Disease and Emergency Preparedness.
The county’s health department had launched an investigation into a potential human case last Friday after preliminary tests indicated the presence of the Yersinia pestis bacteria that causes it.
A positive case was confirmed on Monday. But what are the symptoms people should be looking out for, how is the plague transmitted, and is there a cure?
Bubonic plague is caused by a bacterium called Yersinia pestis, usually found in rodents, small mammals and their fleas.
‘Human to human transmission of bubonic plague is rare’, according to the World Health Organisation (WHO). But every now and then, cases do appear.
People can be infected through flea bites, direct contact with infected bodily fluids, and the inhalation of droplets breathed out by an infected person or animal.
It can only be spread from human to human when the infected person develops pneumonic plague, the most serious form of the disease.
This is how the virus is believed to have wreaked havoc in the Middle Ages, when the a pandemic known as the Black Death wiped out up to half of Europe’s population, making it one of the deadliest in history.
However, body lice may have been just as responsible for spreading the plague as rats and fleas, a recent study suggests.
A lab study suggests that human body lice are more efficient at transmitting Yersinia pestis than previously thought.
The findings, published in the journal PLoS Biology, support the possibility that the parasites may have contributed to previous pandemics.
Dr David Bland conducted the research with colleagues at the United States National Institute of Allergy and Infectious Diseases based in Maryland.
‘Y. pestis has been the culprit behind numerous pandemics, including the Black Death of the Middle Ages that killed millions of people in Europe,’ he said.
‘It naturally cycles between rodents and fleas, and fleas sometimes infect humans through bites – thus, fleas and rats are thought to be the primary drivers of plague pandemics.
‘Body lice – which feed on human blood – can also carry Y. pestis, but are widely considered to be too inefficient at spreading it to contribute substantially to outbreaks.
‘However, the few studies that have addressed lice transmission efficiency have disagreed considerably.’
Dr Bland and his team conducted a series of lab experiments in which body lice fed on blood samples containing Y. pestis.
The experiments involved the use of membrane feeders, which simulate warm human skin, enabling the team to study transmission potential in a lab setting.
They discovered that the body lice became infected with Y. pestis and were capable of routinely transmitting it after feeding on blood containing levels of the pathogen similar to those found in actual human plague cases.
The team also found that Y. pestis can infect a pair of salivary glands found in body lice known as the Pawlowsky glands.
And lice with infected Pawlowsky glands transmitted the pathogen more consistently than lice whose infection was limited to their digestive tract.
It is believed that Pawlowsky glands secrete lubricant onto the lice’s mouthparts.
That led the research team to hypothesise that, in infected lice, such secretions may contaminate mouthparts with Y. pestis, which may in turn spread to humans when bitten.
Dr Bland said: ‘These findings suggest that body lice may be more efficient spreaders of Y. pestis than previously thought, and they could have played a role in past plague outbreaks.’
Plague has been found in animals, and has caused human epidemics, on all continents except Oceania.
There were 3,248 cases, and 584 deaths, reported around the world from 2010 to 2015, BBC News reported.
But it’s been most common in Africa since the 1990s, according to the WHO.
Currently Madagascar, which reports up to 700 cases each year, is one of the three most endemic countries, along with the Democratic Republic of Congo and Peru.
That doesn’t mean countries like the USA are entirely plague-free though.
It has an average of seven reported cases each year, according to the country’s Centers for Disease Control and Prevention (CDC).
Most are in the rural west of the USA.
Oregon confirmed its first case of bubonic plague in nearly a decade just this year, in February, after a man caught it from his pet cat.
Just a month later, a man died of the disease in New Mexico’s Lincoln County.
The north of the state, and southern Oregon, are two of the six areas responsible for most of the USA’s human cases, according to the CDC.
Northern Arizona, southern Colorada, California and far western Nevada are also on the list.
The USA’s last urban plague pandemic occurred in Los Angeles, California and ended in 1925, some 25 years after it was introduced by rat-infested steamships.
Symptoms can appear anywhere between one to eight days after infection.
The first sign is one or more inflamed, tense and painful lymph node – called a ‘bubo’ – usually the closest to the bite where the bacteria entered the body.
Inflamed lymph nodes can turn into open pus-filled sores as the disease advances, according to the WHO.
Bubonic plague patients may also experience symptoms like fever, headache, chills and weakness.
If the disease spreads to the lungs, it can cause shortness of breath, chest pain, coughs and, sometimes, bloody or watery mucous. This is known as pneumonic plague.
Left untreated, bubonic plague can cause tissue necrosis, which is when skin and other tissues on the fingers, toes, noes and other areas turn black and die.
Gone are the days when patients were bled with leeches, or children were encouraged to smoke to keep away the ‘bad air’ people thought caused the plague.
Now it can be relatively easily treated with antibiotics, meaning it’s no longer the near-total death sentence it was in the 14th century.
The key to survival is early diagnosis and treatment, which are much less likely if people don’t know what to look out for or lack access to adequate health facilities.
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