Thursday, October 23, 2014

Airborne Spread of Ebola from Pigs to Macaques/ Nature

Not sure why this is still a subject for debate.  Animal models establish that Ebola can be transmitted via aerosol secretions under lab conditions.  The question remaining is how often this happens in humans. Maybe it does; maybe it doesn't.

Despite CDC protestations regarding airborne spread, the new guidelines for personal protective equipment issued by CDC on Oct 20 demonstrate that CDC is as concerned as I am about aerosolized droplet spread of Ebola. These measures include:
  • Respirators, including either N95 respirators or powered air purifying respirator(PAPR)
  • Single-use, full-face shield that is disposable
  • Surgical hoods to ensure complete coverage of the head and neck
Here is the Nature article that got a lot of attention, in which pigs spread Ebola to macaques in a nearby cage via aerosols.  Here is a pdf of the article.

Transmission of Ebola virus from pigs to non-human primates
Hana M. WeingartlCarissa Embury-HyattCharles NfonAnders LeungGreg Smith, Gary Kobinger    15 November 2012

Ebola viruses (EBOV) cause often fatal hemorrhagic fever in several species of simian primates including human. While fruit bats are considered natural reservoir, involvement of other species in EBOV transmission is unclear. In 2009, Reston-EBOV was the first EBOV detected in swine with indicated transmission to humans. In-contact transmission of Zaire-EBOV (ZEBOV) between pigs was demonstrated experimentally. Here we show ZEBOV transmission from pigs to cynomolgus macaques without direct contact. Interestingly, transmission between macaques in similar housing conditions was never observed. Piglets inoculated oro-nasally with ZEBOV were transferred to the room housing macaques in an open inaccessible cage system. All macaques became infected. Infectious virus was detected in oro-nasal swabs of piglets, and in blood, swabs, and tissues of macaques. This is the first report of experimental interspecies virus transmission, with the macaques also used as a human surrogate. Our finding may influence prevention and control measures during EBOV outbreaks.

And from the Discussion:

"The present study provides evidence that infected pigs can efficiently transmit ZEBOV to NHPs in conditions resembling farm setting. Our findings support the hypothesis that airborne transmission may contribute to ZEBOV spread, specifically from pigs to primates, and may need to be considered in assessing transmission from animals to humans in general. The present experimental findings would explain REBOV seropositivity of pig farmers in Philippines23 that were not involved in slaughtering or had no known contact with contaminated pig tissues." 

1 comment:

SatyaPranava said...

Osterholm in his Johns Hopkins presentation on the 14th made reference to a researcher who demonstrated the airborne transmission...I guess we await publication.

Keep up the good work.