30 November 2017
A possible alternative route for MERS
Published online 22 November 2017
New research may explain why MERS infections occur even without direct contact with camels or other carriers.
Middle East respiratory syndrome coronavirus (MERS-CoV), a novel virus first identified in 2012, causes a human respiratory infection leading to severe pneumonia.
MERS remains a health threat in the Middle Eastern region. According to a recent World Health Organisation report, the National IHR Focal Point of the Kingdom of Saudi Arabia reported 12 additional cases of MERS-CoV infection, including two deaths, between 27 September and 31 October 2017.
The transmission of the virus from dromedary camels to humans, or from human to human has been well documented. However, there have also been many MERS cases that have occurred with no direct contact with infected individuals or camels.
This prompted Jie Zhou and colleagues, including Ziad Memish, affiliated with Alfaisal University in Saudi Arabia, to investigate whether the gastrointestinal tract could be an alternative infection route for MERS-CoV. The researchers show that human primary intestinal epithelial cells are highly susceptible to MERS-CoV and could sustain robust viral replication. They validated these results using small intestine explants and intestinal organoids.
Their investigation also found MERS-CoV nucleic acids in a stool specimen of a clinical patient. The MERS-CoV virus was considerably resistant to fed-state gastrointestinal fluids, as per their findings, but less tolerant to highly acidic fasted-state gastric fluid.
Finally, the team directly inoculated MERS-CoV into the intestinal tract of a mouse model engineered with the human MERS-CoV receptor DPP4, causing a lethal infection.
Histological analysis revealed that the progression of the enteric infection, was associated with inflammation, virus-positive cells, and live viruses in the lung tissues, suggesting the development of a sequential respiratory infection.
The authors claim that since the intestinal tract can serve as an alternative route of MER-CoV infection, their study could help improve intervention and prevention strategies to stop the spread of the MERS epidemic.
David Hawkes, an Australian molecular virologist, who was not affiliated with this study, agrees that the results should prompt questions about changing prevention strategies for MERS. However, he also highlighted that this finding is a starting point for further research on whether (and for how long) MERS-CoV can survive in a body of water and if there is “a cohort of non-symptomatic people who can shed the virus through their intestinal system,” contributing to the MERS epidemic.
- Zhou, J. et al. Human intestinal tract serves as an alternative infection route for Middle East respiratory syndrome coronavirus. Science Advances http://dx.doi.org/10.1126/sciadv.aao4966 (2017).