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Secondary transmission of airborne Ebola

Hans Andersson hasse at panix.com
Fri Feb 9 01:14:03 EST 1996


NEW EBOLA REPORTS FROM USAMRIID

Based on a case report suggesting that interferon might be effective in
the treatment of Ebola  USAMRIID designed an experiment to evaluate the
therapeutic efficacy  of alpha-interferon for Ebola virus.  The result
showed that interferon treatment was ineffective.  

The report is published in the February issue of Archives of Pathology and
Laboratory Medicine, Vol. 120: Jaax NK, Davis KJ, Geisbert TJ, et al.
"Lethal experimental infection of rhesus monkeys with Ebola-Zaire
(Mayinga) virus by the oral and conjunctival route of exposure".





TRANSMISSION OF EBOLA VIRUS (ZAIRE STRAIN) TO UNINFECTED CONTROL MONKEYS
IN A BIOCONTAINMENT LABORATORY

This USAMRIID report, based on the same experiment, is published in
Lancet, Vol. 346, December 23/30, 1995, p. 1669-1671: 

SUMMARY:

"Secondary transmission of Ebola virus infection in humans is known to be
caused by direct contact with infected patients or body fluids.  We report
transmission of Ebola virus (Zaire strain) to two of three control rhesus
monkeys (Macaca mulatta) that did not have direct contact with
experimentally inoculated monkeys held in the same room.  The two control
monkeys died from Ebola virus infections at 10 and 11 days after the last
experimentally inoculated monkey had died.  The most likely route of
infection of the control monkeys was aerosol, oral, or conjunctival
exposure to virus-laden droplets secreted or excreted from the
experimentally inoculated monkeys.  These observations suggest approaches
to the study of routes of transmission to and among humans." 

EXCERPTS:

"...all of the monkeys experimentally inoculated intramuscularly with
Ebola-Zaire (Mayinga strain) died between days 7 and 13 after infection. 
The three control and interferon-control monkeys, housed in a bank of
stainless steel cages approximately 3 m away from the cages housing
infected animals, remained normal by all variables assessed (clinical
observation, clinical pathology, and immunofluorescence antibody) for the
duration of the study.  10 days after the last experimentally infected
monkey died (22 days after the inoculation of the experimentally infected
monkeys), one of the two interferon-control monkeys died; the control
monkey died the following day." 

"Infectious virus was recovered from all four tissues examined from the
two naturally infected control animals.  The highest virus concentration
was observed in the lung of the interferon control monkey..."

"Lesions present in the control monkeys were histologically similar to
those of the experimentally infected animals, as well as to previous
reports, including the presence of interstitial pneumonia and severe
disseminated intravascular coagulation.  Both monkeys had large amounts of
Ebola-virus antigen-positive material present in the macrophages,
fibrinocellular thrombi, and inflammatory foci throughout the body. 
Copious amounts of extracellular and intracellular Ebola virus antigen
were present in the liver, spleen, lymph nodes, adrenal gland, small
intestine, and kidney.  In the lung, the control monkey had very heavy
anitigen-positive staining multifocally in the interstitium and alveolar
septa, primarily oriented around terminal bronchioles.  Infrequent small
foci of bronchiolar ephithelium, some alveolar macrophages, and
intravascular fibrinocellular thrombi were also positively stained.  This
lesion pattern was consistent with that previously reported in monkeys
exposed to aerosolised Ebola virus..."

"However, lung tissue of the control monkey harboured more virus than the
lung tissue of the interferon control monkey.  Immununoelectronmicroscopy
confirmed that the filovirus seen in tissue of these monkeys was Ebola
virus."

"The control monkeys' cages were located about 3 m away from the animals
infected experimentally via parenteral inoculation. During the course of
the experiment, blood sampling and viral swab sampling procedures were
always performed first on control animals; individual needles and swabs
were used for every procedure. This practice eliminated the possibility of
inadvertent needles or swab transmission of the virus as a possible mode
of infection. Fomite or contact droplet transmission of the virus between
cages was considered unlikely. Standard procedures in our BL4 containment
laboratories have always been successful in the prevention of transmission
of Ebola or Marburg virus to uninfected animals. Thus, pulmonary,
nasopharyngeal, oral, or conjunctival exposure to airborne droplets of the
virus had to be considered as the most likely mode of infection." 

"Transmission of Ebola virus (Zaire strain) to uninfected control monkeys
in a biocontainment laboratory " - N Jaax, P Jahrling, T Geisbert, J
Geisbert, K Steele, K McKee, D Nagley, E Johnson, G Jaax, C Peters.

--Hans Andersson, NYC
hasse at panix.com



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