Ebola-Reston crosses species barrier from pigs to humans
Scott McPherson
in Politics and government, influenza and infectious diseases
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The proMED email I just received is startling. Apparently the Ebola-Reston substrain, which has been recently documented to have crossed the species barrier to infect pigs, has now had its first known pig-to-human transmission.
This is not small news. Ebola-Reston, which was first discovered in primates in the Philippines, was the topic of the best-selling book The Hot Zone. That seminal work, which started many of us on our infectious disease journeys, documented a fierce substrain of the dreaded Ebola virus that was first subtyped in a group of primates imported from the Philippines to Reston, Virginia. Hence the name Ebola-Reston.
Recently, at two farms in the Philippines, Ebola-reston was found to have jumped from apes to swine. Now, the jump has taken the virus from swine to humans.
While Ebola-Reston is not as bad a strain today as, say, Ebola-Zaire, it is never a good thing to have yet another species jump. Quoting from the proMED email:
Experts said the jump was a concern even if the Ebola-Reston strain of the virus is not as deadly as other strains of the [virus], which can cause incurable haemmorrhagic fever and have a mortality rate of 25 to 90 percent. "Viruses jumping across species is always worrying," said Lo Wing-lok, an infectious diseases expert in Hong Kong. "If it continues to do so, the virus will adapt to the human body or may mutate to become more transmissible among humans."
Although human cases of Ebola Reston in the past have been mild, Lo warned against any complacency. "We can't say for sure that it is not dangerous to man, we have to follow developments very closely," Lo said. "In the past, the infections happened to a very small number of people. But this virus may get magnified in swine and we could get a higher-density virus in the environment and more cases of human infection can occur," he said.
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But a NYT piece just posted said that:
(...) ''Even if the Ebola Reston virus can be shared between pigs and people, there is little chance it will mutate to become more lethal, said Dr. Pierre Rollin, acting chief of special pathogens for the Centers for Disease Control and Prevention, who also visited the Philippines for the investigation.
'This virus is very stable, not like flu or H.I.V.,' he said. 'Previously, when the virus went from primates to humans, it did not change. The identical virus was found in both.'
Also, humans do not carry other members of the filovirus family that could mix with it, the way that influenza strains from birds, pigs and human can swap parts of genes.
The infection does suggest that pigs could transmit lethal Ebola, the villain of germ-terror movies like 'The Hot Zone.' Fortunately, Dr. Rollin noted, there are no large pig-farming operations in Sudan, a Muslim country, in rural Zaire or in most other places where the fatal strains flourish.
'It’s probably a rare event that pigs get infected,' said Dr. Thomas Ksiazek, a pathogens specialist at the University of Texas’s medical school in Galveston. 'It hasn’t led to a past catastrophe. We’d know about a catastrophe.'''
Source: http://www.nytimes.com/2009/01/24/health/24ebola.html?_r=1&partner=rss&emc=rss