Credit CDC PHIL
By now everyone probably knows that one of the prime routes of transmission of the Ebola virus in West Africa came from direct contact during funeral rites with the bodies of the dead. We know from experience that after a person dies from the disease, the body can remain infectious for some time.
The question, not well answered until now, has been for how long?
Today the EID Journal has at least a partial answer, by way of experiments performed by NIH scientists, testing their ability to culture, or detect via rt-PCR testing, the Ebola virus in the remains of 5 cynomolgus macaques previously included in EBOV pathogenesis studies, which were subsequently euthanized.
Although rt-PCR testing is the more sensitive of the two tests, in many cases it can detect viral RNA long after the virus is too degraded to still be infectious. Viral cultures show the pathogen is still viable and able to reproduce, but at a cost of sensitivity.
I’ve only reproduced the abstract, major findings, and summary below. Follow the link to read the entire dispatch, including details on methods and materials. The headline here is that viable Ebola virus could be isolated 7 days post-mortem, and that viral RNA continued to be detectable reliably for 3 weeks and sporadically for up to 10 weeks.
Volume 21, Number 5—May 2015
Joseph Prescott, Trenton Bushmaker, Robert Fischer, Kerri Miazgowicz, Seth Judson, and Vincent J. Munster
Author affiliations: National Institutes of Health, Hamilton, Montana, USA
The ongoing Ebola virus outbreak in West Africa has highlighted questions regarding stability of the virus and detection of RNA from corpses. We used Ebola virus–infected macaques to model humans who died of Ebola virus disease. Viable virus was isolated <7 days posteuthanasia; viral RNA was detectable for 10 weeks.
Assessing the stability of corpse-associated virus and determining the most efficient sampling methods for diagnostics will clarify the safest practices for handling bodies and the best methods for determining whether a person has died of EVD and presents a risk for transmission. To facilitate diagnostic efforts, we studied nonhuman primates who died of EVD to examine stability of the virus within tissues and on body surfaces to determine the potential for transmission, and the presence of viral RNA associated with corpses.
In all samples, RNA was detectable sporadically for the entire 10-week period, except for blood, which had positive results for <9 weeks. Tissue samples were more consistently positive within the first few weeks after euthanasia (Figure 1, panel B). All samples from the liver and lung were positive for the first 3 weeks, and spleen samples were positive for the first 4 weeks, at which time lung and spleen samples were no longer tested because of decay and scarcity of tissue. Muscle sample results were sporadic: a sample from 1 animal was negative at the 1-day time point and at several times throughout sampling.
Viable EBOV was variably isolated from swab from all sampling sites. Among blood samples, those from the body cavity had the highest virus titer (2 × 105 50% tissue culture infectious doses/mL) and longest-lasting isolatable virus (7 days posteuthanasia) (Figure 2, panel A). Consistent with the qRT-PCR results, for swab samples, oral and nasal sample titers were highest, followed by those for blood samples, and relatively high titers were observed <4 days posteuthanasia (Figure 2, panel B). Similar to the qRT-PCR experiments, virus titers were higher in tissue samples than in swab samples but were not as sustained; all tissue samples were positive at day 3 posteuthanasia but negative by day 4.
The efficiency of detecting EBOV from corpse samples has not been systematically studied; this information is needed for interpreting results for diagnostic samples for epidemiologic efforts during outbreaks. We showed that viral RNA is readily detectable from oral and blood swab specimens for <3 weeks postmortem from a monkey carcass that was viremic at the time of death, in environmental conditions similar to those during current outbreak (5).
In summary, we present postmortem serial sampling data for EBOV-infected animals in a controlled environment. Our results show that the EBOV RT-PCR RNA target is highly stable, swabbing upper respiratory mucosa is efficient for obtaining samples for diagnostics, and tissue biopsies are no more effective than simple swabbing for virus detection. These results will directly aid interpretation of epidemiologic data collected for human corpses by determining whether a person had EVD at the time of death and whether contact tracing should be initiated. Furthermore, viable virus can persist for >7 days on surfaces of bodies, confirming that transmission from deceased persons is possible for an extended period after death. These data are also applicable for interpreting samples collected from remains of wildlife infected with EBOV, especially nonhuman primates, and to assess risks for handling these carcasses.