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Re: Ebola Transmission Discussion and More...
(2007 study)
Assessment of the Risk of Ebola Virus Transmission from Bodily Fluids and Fomites
Daniel G. Bausch1,2,
Jonathan S. Towner2,
Scott F. Dowell3,
Felix Kaducu4,
Matthew Lukwiya5,a,
Anthony Sanchez2,
Stuart T. Nichol2,
Thomas G. Ksiazek2 and
Pierre E. Rollin2
...
Discussion
We found EBOV to be shed in a wide variety of bodily fluids during the acute phase of illness, including saliva, breast milk, stool, and tears. In most cases, the infected bodily fluid was not visibly contaminated by blood. Of particular concern is the frequent presence of EBOV in saliva early during the course of disease, where it could be transmitted to others through intimate contact and from sharing food, especially given the custom, in many parts of Africa, of eating with the hands from a common plate. However, the isolation of EBOV from only 1 saliva specimen, in contrast to the 8 that were RT-PCR positive, could suggest that the virus is rapidly inactivated by salivary enzymes or other factors in the oral cavity that are unfavorable to virus persistence and replication. EBOV has been previously documented in saliva by RT-PCR, but no attempt was made to culture virus or to explore the temporal dynamics of virus shedding in that study [12]. Marburg virus, the other member of the Filoviridae family, has been isolated as well as detected by RT-PCR in saliva from a patient with a fatal case of Marburg hemorrhagic fever in the Democratic Republic of the Congo (authors' unpublished data). The higher mortality among patients with RT-PCR-positive saliva likely reflects increased virus shedding in patients with high viremia, which has been previously noted to be an indicator of a poor prognosis [9, 11].
The finding of EBOV in breast milk raises the possibility of direct mother-to-child transmission. In fact, breastfed children of both of the mothers whose milk was later tested in this study died of laboratory-confirmed EHF during early stages of the outbreak. The isolation of virus from breast milk in one case even after clearance from the blood suggests that transmission may occur even during convalescence. It is possible that the mammary gland, like the gonads [5] and chambers of the eye [13, 14], is an immunologically protected site in which clearance of virus is delayed. However, we cannot rule out that the finding simply represents residual EBOV secreted into the milk during the period of viremia but not expressed until some days later, since the patient was not actively breastfeeding during admission in the isolation ward, nor can we determine whether the detected EBOV was actually a component of the milk or, rather, was contained in accompanying macrophages. At any rate, it seems prudent to advise breastfeeding mothers who survive EHF to avoid breastfeeding for at least some weeks after recovery and to provide them with alternative means of feeding their infants.
The isolation of EBOV from semen 40 days after the onset of illness underscores the risk of sexual transmission of the filoviruses during convalescence. Zaire EBOV has been detected in the semen of convalescent patients by virus isolation (82 days) and RT-PCR (91 days) after disease onset [5, 14]. Marburg virus has also been isolated from the semen and linked conclusively to sexual transmission 13 weeks into convalescence [15].
The absence of EBOV infection in multiple tested urine specimens suggests that the virus may not be efficiently filtered in the kidney. Consequently, exposure to urine appears to be of low risk during both acute illness and convalescence. The absence of EBOV in the urine, low prevalence on the skin, and rapid clearance from the saliva in surviving patients provides some reassurance that the risk of secondary transmission from casual contacts, fomites, or the sharing of toilet facilities in the home after discharge from the hospital is minimal. This conclusion is supported by previous empirical observations [5, 6].
Abstinence from sex or the use of condoms during sex, as well as avoidance of breastfeeding and contact with the mucous membranes of the eye for at least 3 months after recovery, are still recommended to avoid possible exposure to EBOV in the aforementioned immunologically protected sites.
Other than in samples grossly contaminated with blood, EBOV was not found by any method on environmental surfaces and by RT-PCR on the skin of only 1 patient. These results suggest that environmental contamination and fomites are not frequent modes of transmission, at least in an isolation ward. However, the infectious dose of EBOV is thought to be low, and neither cell culture nor the RT-PCR assay used for EBOV in this study have not been extensively validated for use in environmental detection. Hence, the sensitivity and specificity are unknown. It is possible that EBOV was present in the environment below the threshold of detection or that environmental surfaces in the isolation ward were, at times, initially contaminated by EBOV but then decontaminated through the daily cleaning routine. However, many of the inanimate objects tested, such as bed frames and bedside chairs, would not routinely be specifically decontaminated with bleach solutions under existing guidelines unless they happened to be visibly contaminated [3], suggesting that environmental contamination did not occur. Taken together with empirical epidemiological observations during outbreaks, our results suggest that current recommendations for the decontamination of filoviruses in isolation wards [3] are effective. The risk from environmental contamination and fomites might vary in the household or other settings where decontamination would be less frequent and thorough, especially if linens or other household materials were to become visibly soiled by blood.
There was a significant discrepancy between the results of virus culture and RT-PCR testing in our study, with many more frequent positive results from RT-PCR. Possible explanations for this finding include virus degradation from breaks in the cold chain during sample collection, storage, and shipping; the greater sensitivity of RT-PCR relative to culture; and, in the case of the saliva specimens, possible virus inactivation by salivary enzymes. The less-than-ideal storage conditions of the specimens in the isolation ward immediately after acquisition and the fact that even the nasal blood from 1 patient was culture negative suggest that some virus degradation indeed occurred. Nevertheless, we cannot exclude the possibility of a true absence of viable virus in the original samples. We hope to be able to repeat this study in the future with better maintenance of the cold chain to resolve this question.
Taken together, our results support the conventional assumptions and field observations that most EBOV transmission comes from direct contact with blood or bodily fluids of an infected patient during the acute phase of illness. The risk of casual contacts with the skin, such as shaking hands, is likely to be low. Environmental contamination and fomites do not appear to pose a significant risk when currently recommended infection control guidelines for the viral hemorrhagic fevers are followed. Prospective studies with the collection of a greater number of clinical samples from patients at different stages of EHF, as well as environmental samples analyzed with an assay validated for EBOV detection in such samples, should be performed to confirm our results.
...
? 2007 by the Infectious Diseases Society of America
http://jid.oxfordjournals.org/content/196/Supplement_2/S142.full
(2007 study)
Assessment of the Risk of Ebola Virus Transmission from Bodily Fluids and Fomites
Daniel G. Bausch1,2,
Jonathan S. Towner2,
Scott F. Dowell3,
Felix Kaducu4,
Matthew Lukwiya5,a,
Anthony Sanchez2,
Stuart T. Nichol2,
Thomas G. Ksiazek2 and
Pierre E. Rollin2
...
Discussion
We found EBOV to be shed in a wide variety of bodily fluids during the acute phase of illness, including saliva, breast milk, stool, and tears. In most cases, the infected bodily fluid was not visibly contaminated by blood. Of particular concern is the frequent presence of EBOV in saliva early during the course of disease, where it could be transmitted to others through intimate contact and from sharing food, especially given the custom, in many parts of Africa, of eating with the hands from a common plate. However, the isolation of EBOV from only 1 saliva specimen, in contrast to the 8 that were RT-PCR positive, could suggest that the virus is rapidly inactivated by salivary enzymes or other factors in the oral cavity that are unfavorable to virus persistence and replication. EBOV has been previously documented in saliva by RT-PCR, but no attempt was made to culture virus or to explore the temporal dynamics of virus shedding in that study [12]. Marburg virus, the other member of the Filoviridae family, has been isolated as well as detected by RT-PCR in saliva from a patient with a fatal case of Marburg hemorrhagic fever in the Democratic Republic of the Congo (authors' unpublished data). The higher mortality among patients with RT-PCR-positive saliva likely reflects increased virus shedding in patients with high viremia, which has been previously noted to be an indicator of a poor prognosis [9, 11].
The finding of EBOV in breast milk raises the possibility of direct mother-to-child transmission. In fact, breastfed children of both of the mothers whose milk was later tested in this study died of laboratory-confirmed EHF during early stages of the outbreak. The isolation of virus from breast milk in one case even after clearance from the blood suggests that transmission may occur even during convalescence. It is possible that the mammary gland, like the gonads [5] and chambers of the eye [13, 14], is an immunologically protected site in which clearance of virus is delayed. However, we cannot rule out that the finding simply represents residual EBOV secreted into the milk during the period of viremia but not expressed until some days later, since the patient was not actively breastfeeding during admission in the isolation ward, nor can we determine whether the detected EBOV was actually a component of the milk or, rather, was contained in accompanying macrophages. At any rate, it seems prudent to advise breastfeeding mothers who survive EHF to avoid breastfeeding for at least some weeks after recovery and to provide them with alternative means of feeding their infants.
The isolation of EBOV from semen 40 days after the onset of illness underscores the risk of sexual transmission of the filoviruses during convalescence. Zaire EBOV has been detected in the semen of convalescent patients by virus isolation (82 days) and RT-PCR (91 days) after disease onset [5, 14]. Marburg virus has also been isolated from the semen and linked conclusively to sexual transmission 13 weeks into convalescence [15].
The absence of EBOV infection in multiple tested urine specimens suggests that the virus may not be efficiently filtered in the kidney. Consequently, exposure to urine appears to be of low risk during both acute illness and convalescence. The absence of EBOV in the urine, low prevalence on the skin, and rapid clearance from the saliva in surviving patients provides some reassurance that the risk of secondary transmission from casual contacts, fomites, or the sharing of toilet facilities in the home after discharge from the hospital is minimal. This conclusion is supported by previous empirical observations [5, 6].
Abstinence from sex or the use of condoms during sex, as well as avoidance of breastfeeding and contact with the mucous membranes of the eye for at least 3 months after recovery, are still recommended to avoid possible exposure to EBOV in the aforementioned immunologically protected sites.
Other than in samples grossly contaminated with blood, EBOV was not found by any method on environmental surfaces and by RT-PCR on the skin of only 1 patient. These results suggest that environmental contamination and fomites are not frequent modes of transmission, at least in an isolation ward. However, the infectious dose of EBOV is thought to be low, and neither cell culture nor the RT-PCR assay used for EBOV in this study have not been extensively validated for use in environmental detection. Hence, the sensitivity and specificity are unknown. It is possible that EBOV was present in the environment below the threshold of detection or that environmental surfaces in the isolation ward were, at times, initially contaminated by EBOV but then decontaminated through the daily cleaning routine. However, many of the inanimate objects tested, such as bed frames and bedside chairs, would not routinely be specifically decontaminated with bleach solutions under existing guidelines unless they happened to be visibly contaminated [3], suggesting that environmental contamination did not occur. Taken together with empirical epidemiological observations during outbreaks, our results suggest that current recommendations for the decontamination of filoviruses in isolation wards [3] are effective. The risk from environmental contamination and fomites might vary in the household or other settings where decontamination would be less frequent and thorough, especially if linens or other household materials were to become visibly soiled by blood.
There was a significant discrepancy between the results of virus culture and RT-PCR testing in our study, with many more frequent positive results from RT-PCR. Possible explanations for this finding include virus degradation from breaks in the cold chain during sample collection, storage, and shipping; the greater sensitivity of RT-PCR relative to culture; and, in the case of the saliva specimens, possible virus inactivation by salivary enzymes. The less-than-ideal storage conditions of the specimens in the isolation ward immediately after acquisition and the fact that even the nasal blood from 1 patient was culture negative suggest that some virus degradation indeed occurred. Nevertheless, we cannot exclude the possibility of a true absence of viable virus in the original samples. We hope to be able to repeat this study in the future with better maintenance of the cold chain to resolve this question.
Taken together, our results support the conventional assumptions and field observations that most EBOV transmission comes from direct contact with blood or bodily fluids of an infected patient during the acute phase of illness. The risk of casual contacts with the skin, such as shaking hands, is likely to be low. Environmental contamination and fomites do not appear to pose a significant risk when currently recommended infection control guidelines for the viral hemorrhagic fevers are followed. Prospective studies with the collection of a greater number of clinical samples from patients at different stages of EHF, as well as environmental samples analyzed with an assay validated for EBOV detection in such samples, should be performed to confirm our results.
...
? 2007 by the Infectious Diseases Society of America
http://jid.oxfordjournals.org/content/196/Supplement_2/S142.full
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