The Black Death possibly not bubonic plague

[Frozen Hamster]

Ever since Alexandre Yersin isolated the bacteria Yersina pestis and determined that it caused bubonic plague and was carried by rodents it has been assumed that the Black Death which decimated Europe during the 14th century was bubonic plague passed on by fleas from rats. In recent years this explanation has been called into question.

Biologist Örnólfur Thorlacius hypothesizes in the latest edition of Náttúrufræðingurinn (The Naturalist), a magazine published by the Icelandic Nature Organization, that the Black Death was not bubonic plague but a virus similar to the Ebola, Lassa or Marburg virii. This hypothesis is mostly based on the research of Susan Scott and Duncan Christopher

Thorlacius main argument is that the Black Death decimated the population of Iceland, but at that time there was no permanent population of rats in Iceland. Although black rats must have been introduced to Iceland via ships they have never survived for any length of time until the 19th-20th century. Most scientists that have studied bubonic plague agree that it can not be spread by humans unless the bacteria is present in a population of wild rodents.

Also these rodents must be able to survive the disease. Bubonic plague is fatal to black rats. Thorlacius quotes Scott and Christopher saying that "no known rodent in Europe, now or in the past, tolerates Y. pestis to such an extent that the bacterium remains in wild population for a significant amount of time."

Bubonic plague has arrived to Europe via ships but has never penetrated far inland.

Scott and Christopher discovered during their research that the gestation period of the disease was 32 days, as opposed to the 2-5 days of bubonic plague.

[DemBones DemBones]

1. It's an interesting question. I think the incidence of

plague in Iceland might be explained by pneumonic transmission. The rats wouldn't have to get off the ships as long as some infected sailors did. Infected crewmen could spread the disease to a number of Icelanders and then it could, I think, be spread from Icelander to Icelander without a reservoir host. The absence of a reservoir host would mean the plague would disappear after a time, as it did.

There's also the probability that crew from more than one ship would include infected sailors who went ashore and spread the plague.

[zalinda]

2. But, didn't it take months for the ships

to cross the ocean? If there is a gestation period of 3-5 days then there would have been very few survivors to land in Iceland.

zalinda

[DemBones DemBones]

5. Plague didn't kill everyone who got it and

even if most of a crew had it on a voyage (which is probably very unlikely -- many would have already had it and survived) they wouldn't all have it at the same time. They would likely know enough to isolate anyone who got sick and keep it from spreading pneumonically, or at least limit the spread.

The other way ships spread plague was by carrying infected rats from one port to another. At least, that's been the long-held theory: that rats brought bubonic plague into a city but plague was also transmitted person to person, though it also became endemic in the local rat (or other rodent) population.

[Frozen Hamster]

8. The problem with the second hypothesis is

that bubonic plague kills rats too so if they were carrying the plague aboard the ship all rats would probably be dead before it landed in Iceland.

[DemBones DemBones]

9. Why would all the rats on a ship get the plague?

Or die from it? If Yersinia pestis killed all infected rats or other rodents wouldn't it kill all its reservoir hosts?

[Frozen Hamster]

3. The Black Death epidemic raged for two years

(1402-1404) in Iceland and spread through-out the land. At that time most trade went through two ports on the country, Iceland has always been sparsely populated and, as I said, no rat population to carry bubonic plague, and bubonic plague needs to be in a local population of rodents if it is to spread via human-human contact.

[DemBones DemBones]

6. Has it been conclusively established that Y. pestis

must be endemic in a local rodent population to set up an epidemic like the one in Iceland? The article you cited is asserting a new hypothesis, that plague is not caused by Y. pestis, so as long as we're questioning one long-held hypothesis, why not another?

[Frozen Hamster]

7. According to Thorlacius everyone who has studied

bubonic plague agrees that it is necessary

[phantom power]

4. I'm surprised that a filovirus would have such a long incubation time

Ebola and Marburg run their entire course in 10 days or less. 32 days seems quite long, by comparison.

[Skinner]

10. Got a link for this?

Thanks.

[Frozen Hamster]

11. Afraid not

As far as I know Náttúrufræðingurinn is not published on the Internet and I haven't found this article anywhere else.

[DemBones DemBones]

12. Can you clarify for me if Thorlacius

simply wrote an article reviewing the research of Scott and ________ and perhaps formed some hypotheses of his own, or did he do some research as well?

In any case, I'll Google all three names and see what other new info on plague I can find, too, as I've always been interested in epidemics and epizootics and the ecological factors involved, took a CDC course in basic epidemiology and used to read the MMWR weekly, etc. A fascinating field but the entry-level positions (VD investigators who go door to door tracing the infected person's sexual contacts) are a little scary. The only woman I know who's done that job (and moved up) told me she used to go places where the police refuse to go.

[Frozen Hamster]

13. Thorlacius reviewed the works of

Scott and Duncan and various other scientists and then wrote the article. It has been hypothesized by others (such as Graham Twigg) that certain localized epidemics that have been classified as bubonic plague may have been caused by other pathogens than Y. pestis but as far as I know Thorlacius is the first to hypothesize that the Black Death epidemics were not bubonic plague.