MERS-CoV generally presents as a respiratory illness, and its severity may range from asymptomatic or mild to severe pneumonia. As such, the preferred methods of testing are on sputum, bronchoalveolar lavage (BAL), or other respiratory fluids.
Unlike with most respiratory viruses, viral RNA from MERS-CoV has occasionally been detected in blood, urine, and stool. For an excellent primer on this, you may wish to revisit Dr. Ian Mackay's MERS-CoV in the blood.... from 2014.
This `extrapulmonary' detection of MERS-CoV RNA isn't consistent across the board, although it occurs often enough to pique the interest of researchers looking to better understand the pathology of the virus in the human host.
Which brings us to a new EID Journal Dispatch that looks at viral RNA findings in a subset (33%) of patients tested during Korea's MERS outbreak in the summer of 2015.
While MERS-CoV viremia isn't common enough to make it a satisfactory screening test, researchers did determine that detectable MERS-CoV RNA in the bloodstream was an indicator of more severe disease and a poorer outcome.
I've only posted some excerpts, so follow the link below the read the dispatch in its entirety.
Volume 22, Number 10—October 2016
Viral RNA in Blood as Indicator of Severe Outcome in Middle East Respiratory Syndrome Coronavirus Infection
So Yeon Kim, Sun Jae Park, Sook Young Cho, Ran-hui Cha, Hyeon-Gun Jee, Gayeon Kim, Hyoung-Shik Shin, Yeonjae Kim, Yu Mi Jung, Jeong-Sun Yang, Sung Soon Kim, Sung Im Cho, Man Jin Kim, Jee-Soo Lee, Seung Jun Lee, Soo Hyun Seo, Sung Sup Park, and Moon-Woo SeongComments to Author
We evaluated the diagnostic and clinical usefulness of blood specimens to detect Middle East respiratory syndrome coronavirus infection in 21 patients from the 2015 outbreak in South Korea. Viral RNA was detected in blood from 33% of patients at initial diagnosis, and the detection preceded a worse clinical course.
Middle East respiratory syndrome coronavirus (MERS-CoV) is a zoonotic, betacoronavirus lineage C RNA virus that was first identified in Saudi Arabia in 2012 (1). MERS-CoV causes respiratory and renal illness in humans, and infection often progresses to severe pneumonia, acute respiratory distress syndrome, renal failure, or death in a subset of patients (2). Risk factors, including patient age, preexisting health conditions, and high viral load in upper respiratory specimens, have been suggested to be related to disease severity and death (3,4). However, pathogenesis and clinical characteristics promoting recovery from infection or progression to serious organ failure have not been well elucidated.
Respiratory specimens are preferred for viral RNA detection and confirmatory diagnosis of MERS-CoV infection in humans (5). MERS-CoV has broad tissue tropism, including the kidney, intestinal tract, liver, histiocytes, macrophages, and T lymphocytes, but viral RNA has been found inconsistently in blood, urine, and fecal specimens (6–10). Reports have described small numbers of cases with extrapulmonary virus; therefore, it remains unclear whether extrapulmonary specimens have any diagnostic usefulness in determining infection or whether extrapulmonary viral detection has clinical implications in disease management.
A large MERS-CoV outbreak occurred in 2015 in South Korea. This outbreak comprised the first imported case and subsequent infection of 185 patients (11). Our study aimed to evaluate the diagnostic utility of blood specimens for MERS-CoV infection by using large numbers of patients with a single viral origin and to determine the relationship between blood viral detection and clinical characteristics.
ConclusionsOur data showed a detection rate of 33% for viral RNA in blood at initial diagnosis, which was insufficient for initial confirmatory diagnosis. Blood viral RNA at the early phase was related to a worse clinical course in infected patients and might be a good prognostic indicator of severe outcome. Measuring blood viral RNA at hospital admission might be useful.
Dr. Kim is a medical doctor at the Department of Laboratory Medicine of National Medical Center in South Korea. Her research interests include molecular diagnostics and infectious diseases.