Friday, December 9, 2016

Is Smallpox a new disease?

tech times:

new analysis of smallpox DNA from the 17th century suggests smallpox might have recently evolved and does not date into prehistory as many had thought.

The disease had long been believed to have emerged among humans thousands of years ago, afflicting people in India, Egypt, and China. Some historical accounts even suggest the Egyptian pharaoh Ramses V, who passed away in 1145 B.C., had been struck by smallpox.

For the study that involved the genetic analysis of the viral DNA taken from the partially mummified remains of a child dating back from the 17th century, researchers found that the smallpox could be just some hundreds of years old.

measles is considered to be a "new" disease also, so questions if ancient plagues were measles are also at question. Measles evolved from the animal disease Rinerpest in the 11th century.

so what caused earlier plagues?

One problem is that diseases sort of change with time.

Often they are very virulent when they first hit humans, then because killing one's host is not very beneficial for your evolution, the variation of the germ that doesn't kill quickly (and hence, spreads to more people) wins the evolutionary battle.

DNA has helped to identify ancient diseases: there is some evidence that Justinian plague was actually Bubonic plague, and some studies of the plague of Athens suggest it might have been typhoid.

and they are still debating what caused the Antonine plague (which weakened the Roman Empire and killed Marcus Aurelius, the emperor in Gladiator). Since the soldiers caught it from "Parthia", a dry climate, one suspects it could be bubonic plague or a similar zoonosis.

but it also does mention the Chinese in 1000 AD devised innoculation with smallpox scabs to stop the disease from spreading (other stories insist it was Africans or the Arabs who did this. A lot of the Africans brought to the Americas were from Muslim areas and the Arabs were in touch with China so maybe the idea spread? The English started to use it from the Ottoman empire contacts.

on the other hand,

Until the 18th century, inoculation was a practice largely confined to China, India, Turkey, and other eastern countries. 
Lady Mary Montagu, an aristocrat and the wife of England’s ambassador to Turkey, is credited as being the first to bring attention to the practice in the Western world. In 1715, Montagu had gone through her own bout of smallpox, and had been disfigured as a result. After learning about inoculation during her time in Turkey, she was determined to protect her six-year-old son from the disease through inoculation.

One possible reason for the confusion is that there are two variations of smallpox: One with a very high mortality, and one with a lower mortality.

the latest case that suggested a recent evolution of the virus ignores non DNA evidence from the past

So is smallpox old or new, or something that just pops up now and then?  LINK and LINK (these are long MEGO type articles that I will have to read in detail later).

but this is one puzzle:

As variola virus lacks a known non-human animal reservoir, its origin as a human pathogen has been concealed under a veil of mystery. The evolutionary history of this virus can be dated based on either the assumed dates of variola virus subtypes diverging from the ancestors, or the dates of isolated samples that contain variola virus.
the problem with the smallpox family of viruses is that they mutate quickly, and humans can catch pox viruses from animals: The most famous example of this is Jenner's observation that milkmaids who caught cowpox never caught smallpox, and devised vaccination.

but other animal pox could cause problems: in recent years, there have been reported cases of monkeypox in humans.

and then there is camelpox:

Phylogenetic reconstructions suggest that camelpox virus, taterapox virus and variola virus emerged from a common progenitor almost simultaneously. Additionally, these viruses are strictly specific for their hosts, and both variola virus and camelpox virus cause diseases with high case fatality rates.

However, the real puzzle about human smallpox is that so far they haven't discovered an animal who carries it, i.e. a reservoir where it hides.

sow what does this mean?

It means a new outbreak could pop up from animals, mutate and kill thousands of people

Recent oubreaks of "new" diseases like SARS (in China), MERS (in the Middle East) and cases of avian flu in humans so far haven't killed millions mainly due to old fashioned ways of stopping the spread of the virus, e.g. washing hands, isolation, and stopping travelers.

 and of course outbreaks of known diseases like Zika and Ebola are also a worry.
But small pox? Spread via the air to people nearby, long incubatio perios, and no one except some of the military and first responders who have had immunity suggest a problem.

But at least with smallpox, there is a vaccine.

And the real worry: What if a newer variation, such as weaponized monkeypox or camelpox that evolves ?

again, the bad old days of quarrentine will return.

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