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# 8445
Although limited human-to-human transmission of the MERS Coronavirus has been established, and there’s pretty good evidence to suggest repeated introduction of the virus to humans via camels (see CIDRAP NEWS report WHO sees camels as MERS source, but route uncertain), the full ecology of this virus remains murky at best.
Today we’ve a letter that appears in the CDC’s EID Journal that looks at whether unpasteurized milk could serve as a possible source of human infection.
Previously, in Eurosurveillance: Environmental Stability Of MERS-CoV, we looked at research that found - under the right conditions - the MERS virus could remain viable outside a living host for a prolonged period of time. Among their findings:
- While the Influenza A virus became non-viable on steel and plastic surfaces in less than 4 hours for all testing environments, the MERS virus survived 48 hours in the 20°C – 40% RH environment. Survival of the coronavirus at 30°C – 30% RH was 24 hours, and 8 hours at 30°C – 80% RH.
- As an aerosol, the MERS virus remained very stable at 20°C – 40% RH, while its viability decreased (89% – comparable to the Influenza A virus) at 20°C – 70% RH.
In today’s report researchers inoculated various types of milk products (camel, goat, cow, etc.) and DMEM (a cell culture media) with MERS-CoV strain Jordan-N3/2012, stored multiple samples at 4°C or 22°C, and then tested their infectious disease titers at 0, 8, 24, 48, 72 hours post dilution.
Their results?
At 0–72 hpd, virus titers decreased significantly only in goat milk (p = 0.0139, 1-tailed paired t test) and DMEM (p = 0.0311) but not in dromedary camel milk (p = 0.1414) or cow milk (p = 0.2895). Samples stored at 22°C showed a greater loss of infectivity than did samples stored at 4°C.
Making unpasteurized milk at least a plausible medium for carriage of the MERS virus or its transmission to humans.
I’ve excerpted a few paragraphs, but you’ll want to read the entire letter for details on materials and methods used.
Volume 20, Number 7—July 2014
Letter
Stability of Middle East Respiratory Syndrome Coronavirus in Milk
van Doremalen N, Bushmaker T, Karesh WB, Munster VJ.
To the Editor: Middle East respiratory syndrome coronavirus (MERS-CoV) was first diagnosed in humans in 2012. Human-to-human transmission of MERS-CoV has been limited, and the transmission route is still unclear. On the basis of epidemiologic studies, involvement of an animal host has been suggested (1). Dromedary camels have been identified as a possible intermediate host on the basis of MERS-CoV antibodies and detection of MERS-CoV viral RNA in respiratory swab samples (1–3). Furthermore, MERS-CoV genome sequences obtained from dromedary camels clustered with MERS-CoV sequences obtained from humans linked to the same farm (2). Nonetheless, most persons with MERS-CoV did not report any direct contact with dromedary camels; therefore, how MERS-CoV zoonotic transmission occurs is unclear. MERS-CoV replicates in cell lines originating from a wide variety of different hosts, which suggests the potential for a broader reservoir species range then currently recognized (4). However, unlike in dromedary camels, no serologic evidence pointing toward MERS-CoV infection has been found in goats, sheep, and cows (1).
Contamination of dairy products has been associated with transmission of bacteria and viruses. Shedding of infectious tick-borne encephalitis virus in milk was detected after experimental infection of goats, and the consumption of raw milk has been associated with tick-borne encephalitis virus clusters (5). Similarly, cattle can be infected with foot-and-mouth disease through consumption of raw contaminated milk (6).
<SNIP>
Residents of the Arabian Peninsula commonly drink unpasteurized milk. Our results show that MERS-CoV, when introduced into milk, can survive for prolonged periods. Further study is needed to determine whether MERS-CoV is excreted into the milk of infected dromedary camels and, if so, whether handling or consuming contaminated milk is associated with MERS-CoV infection.
(Continue . . . )
