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Perlman S, Azhar EI, Memish ZA, Hui DS, Zumla A. Confronting the persisting threat of the Middle East respiratory syndrome to global health security. THE LANCET. INFECTIOUS DISEASES 2019; 20:158-160. [PMID: 31279728 PMCID: PMC7128339 DOI: 10.1016/s1473-3099(19)30347-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 06/12/2019] [Indexed: 12/22/2022]
Affiliation(s)
- Stanley Perlman
- Department of Microbiology and Immunology and Department of Pediatrics, University of Iowa, Iowa City, IA 52242, USA.
| | - Esam I Azhar
- Special Infectious Agents Unit, King Fahd Medical Research Centre and Department of Medical Laboratory Technology, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Ziad A Memish
- Infectious Diseases Division, Department of Medicine and Department of Research, Prince Mohamed Bin Abdulaziz Hospital, Riyadh, Saudi Arabia; Ministry of Health and College of Medicine, Alfaisal University, Riyadh, Saudi Arabia; Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, GA, USA
| | - David S Hui
- Division of Respiratory Medicine and Stanley Ho Center for Emerging Infectious Diseases, The Chinese University of Hong Kong, Prince of Wales Hospital, New Territories, Hong Kong, China
| | - Alimuddin Zumla
- Division of Infection and Immunity, Center for Clinical Microbiology, University College London, London, UK; NIHR Biomedical Research Centre, UCL Hospitals NHS Foundation Trust, London, UK
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Widagdo W, Okba NMA, Richard M, de Meulder D, Bestebroer TM, Lexmond P, Farag EABA, Al-Hajri M, Stittelaar KJ, de Waal L, van Amerongen G, van den Brand JMA, Haagmans BL, Herfst S. Lack of Middle East Respiratory Syndrome Coronavirus Transmission in Rabbits. Viruses 2019; 11:v11040381. [PMID: 31022948 PMCID: PMC6520746 DOI: 10.3390/v11040381] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 04/09/2019] [Accepted: 04/22/2019] [Indexed: 12/12/2022] Open
Abstract
Middle East respiratory syndrome coronavirus (MERS-CoV) transmission from dromedaries to humans has resulted in major outbreaks in the Middle East. Although some other livestock animal species have been shown to be susceptible to MERS-CoV, it is not fully understood why the spread of the virus in these animal species has not been observed in the field. In this study, we used rabbits to further characterize the transmission potential of MERS-CoV. In line with the presence of MERS-CoV receptor in the rabbit nasal epithelium, high levels of viral RNA were shed from the nose following virus inoculation. However, unlike MERS-CoV-infected dromedaries, these rabbits did not develop clinical manifestations including nasal discharge and did shed only limited amounts of infectious virus from the nose. Consistently, no transmission by contact or airborne routes was observed in rabbits. Our data indicate that despite relatively high viral RNA levels produced, low levels of infectious virus are excreted in the upper respiratory tract of rabbits as compared to dromedary camels, thus resulting in a lack of viral transmission.
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Affiliation(s)
- W Widagdo
- Department of Viroscience, Erasmus Medical Center, 3015GD Rotterdam, The Netherlands.
| | - Nisreen M A Okba
- Department of Viroscience, Erasmus Medical Center, 3015GD Rotterdam, The Netherlands.
| | - Mathilde Richard
- Department of Viroscience, Erasmus Medical Center, 3015GD Rotterdam, The Netherlands.
| | - Dennis de Meulder
- Department of Viroscience, Erasmus Medical Center, 3015GD Rotterdam, The Netherlands.
| | - Theo M Bestebroer
- Department of Viroscience, Erasmus Medical Center, 3015GD Rotterdam, The Netherlands.
| | - Pascal Lexmond
- Department of Viroscience, Erasmus Medical Center, 3015GD Rotterdam, The Netherlands.
| | | | | | | | - Leon de Waal
- Viroclinics Biosciences BV, Rotterdam 3029 AK, The Netherlands.
| | | | | | - Bart L Haagmans
- Department of Viroscience, Erasmus Medical Center, 3015GD Rotterdam, The Netherlands.
| | - Sander Herfst
- Department of Viroscience, Erasmus Medical Center, 3015GD Rotterdam, The Netherlands.
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Mishra N, Fagbo SF, Alagaili AN, Nitido A, Williams SH, Ng J, Lee B, Durosinlorun A, Garcia JA, Jain K, Kapoor V, Epstein JH, Briese T, Memish ZA, Olival KJ, Lipkin WI. A viral metagenomic survey identifies known and novel mammalian viruses in bats from Saudi Arabia. PLoS One 2019; 14:e0214227. [PMID: 30969980 PMCID: PMC6457491 DOI: 10.1371/journal.pone.0214227] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Accepted: 03/09/2019] [Indexed: 12/31/2022] Open
Abstract
Bats are implicated as natural reservoirs for a wide range of zoonotic viruses including SARS and MERS coronaviruses, Ebola, Marburg, Nipah, Hendra, Rabies and other lyssaviruses. Accordingly, many One Health surveillance and viral discovery programs have focused on bats. In this report we present viral metagenomic data from bats collected in the Kingdom of Saudi Arabia [KSA]. Unbiased high throughput sequencing of fecal samples from 72 bat individuals comprising four species; lesser mouse-tailed bat (Rhinopoma hardwickii), Egyptian tomb bat (Taphozous perforatus), straw-colored fruit bat (Eidolon helvum), and Egyptian fruit bat (Rousettus aegyptiacus) revealed molecular evidence of a diverse set of viral families: Picornaviridae (hepatovirus, teschovirus, parechovirus), Reoviridae (rotavirus), Polyomaviridae (polyomavirus), Papillomaviridae (papillomavirus), Astroviridae (astrovirus), Caliciviridae (sapovirus), Coronaviridae (coronavirus), Adenoviridae (adenovirus), Paramyxoviridae (paramyxovirus), and unassigned mononegavirales (chuvirus). Additionally, we discovered a bastro-like virus (Middle East Hepe-Astrovirus), with a genomic organization similar to Hepeviridae. However, since it shared homology with Hepeviridae and Astroviridae at ORF1 and in ORF2, respectively, the newly discovered Hepe-Astrovirus may represent a phylogenetic bridge between Hepeviridae and Astroviridae.
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Affiliation(s)
- Nischay Mishra
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, New York, United States of America
- * E-mail: (NM); (ZAM)
| | - Shamsudeen F. Fagbo
- One Health Unit, Executive Directorate for Surveillance and Response, National Center for Disease Prevention and Control, Riyadh, Saudi Arabia
| | - Abdulaziz N. Alagaili
- KSU Mammals Research Chair, Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Adam Nitido
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, New York, United States of America
| | - Simon H. Williams
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, New York, United States of America
| | - James Ng
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, New York, United States of America
| | - Bohyun Lee
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, New York, United States of America
| | | | - Joel A. Garcia
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, New York, United States of America
| | - Komal Jain
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, New York, United States of America
| | - Vishal Kapoor
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, New York, United States of America
| | | | - Thomas Briese
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, New York, United States of America
| | - Ziad A. Memish
- The College of Medicine, Al faisal University & Prince Mohammed Bin Abdulaziz Hospital, Ministry of Health, Riyadh, Kingdom of Saudi Arabia
- * E-mail: (NM); (ZAM)
| | - Kevin J. Olival
- EcoHealth Alliance, New York, New York, United States of America
| | - W. Ian Lipkin
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, New York, United States of America
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Skariyachan S, Challapilli SB, Packirisamy S, Kumargowda ST, Sridhar VS. Recent Aspects on the Pathogenesis Mechanism, Animal Models and Novel Therapeutic Interventions for Middle East Respiratory Syndrome Coronavirus Infections. Front Microbiol 2019; 10:569. [PMID: 30984127 PMCID: PMC6448012 DOI: 10.3389/fmicb.2019.00569] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2018] [Accepted: 03/05/2019] [Indexed: 12/17/2022] Open
Abstract
Middle East Respiratory Syndrome Coronavirus (MERS-CoV) is an emerging zoonotic virus considered as one of the major public threat with a total number of 2 298 laboratory-confirmed cases and 811 associated deaths reported by World Health Organization as of January 2019. The transmission of the virus was expected to be from the camels found in Middle Eastern countries via the animal and human interaction. The genome structure provided information about the pathogenicity and associated virulent factors present in the virus. Recent studies suggested that there were limited insight available on the development of novel therapeutic strategies to induce immunity against the virus. The severities of MERS-CoV infection highlight the necessity of effective approaches for the development of various therapeutic remedies. Thus, the present review comprehensively and critically illustrates the recent aspects on the epidemiology of the virus, the structural and functional features of the viral genome, viral entry and transmission, major mechanisms of pathogenesis and associated virulent factors, current animal models, detection methods and novel strategies for the development of vaccines against MERS-CoV. The review further illustrates the molecular and computational virtual screening platforms which provide insights for the identification of putative drug targets and novel lead molecules toward the development of therapeutic remedies.
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Affiliation(s)
- Sinosh Skariyachan
- R&D Centre, Department of Biotechnology, Dayananda Sagar College of Engineering, Bengaluru, India
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Gardner EG, Kelton D, Poljak Z, Van Kerkhove M, von Dobschuetz S, Greer AL. A case-crossover analysis of the impact of weather on primary cases of Middle East respiratory syndrome. BMC Infect Dis 2019. [PMID: 30717685 DOI: 10.1186/s12879-019-3729-%205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/21/2023] Open
Abstract
BACKGROUND Middle East respiratory syndrome coronavirus (MERS-CoV) is endemic in dromedary camels in the Arabian Peninsula, and zoonotic transmission to people is a sporadic event. In the absence of epidemiological data on the reservoir species, patterns of zoonotic transmission have largely been approximated from primary human cases. This study aimed to identify meteorological factors that may increase the risk of primary MERS infections in humans. METHODS A case-crossover design was used to identify associations between primary MERS cases and preceding weather conditions within the 2-week incubation period in Saudi Arabia using univariable conditional logistic regression. Cases with symptom onset between January 2015 - December 2017 were obtained from a publicly available line list of human MERS cases maintained by the World Health Organization. The complete case dataset (N = 1191) was reduced to approximate the cases most likely to represent spillover transmission from camels (N = 446). Data from meteorological stations closest to the largest city in each province were used to calculate the daily mean, minimum, and maximum temperature (οC), relative humidity (%), wind speed (m/s), and visibility (m). Weather variables were categorized according to strata; temperature and humidity into tertiles, and visibility and wind speed into halves. RESULTS Lowest temperature (Odds Ratio = 1.27; 95% Confidence Interval = 1.04-1.56) and humidity (OR = 1.35; 95% CI = 1.10-1.65) were associated with increased cases 8-10 days later. High visibility was associated with an increased number of cases 7 days later (OR = 1.26; 95% CI = 1.01-1.57), while wind speed also showed statistically significant associations with cases 5-6 days later. CONCLUSIONS Results suggest that primary MERS human cases in Saudi Arabia are more likely to occur when conditions are relatively cold and dry. This is similar to seasonal patterns that have been described for other respiratory diseases in temperate climates. It was hypothesized that low visibility would be positively associated with primary cases of MERS, however the opposite relationship was seen. This may reflect behavioural changes in different weather conditions. This analysis provides key initial evidence of an environmental component contributing to the development of primary MERS-CoV infections.
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Affiliation(s)
- Emma G Gardner
- Ontario Veterinary College, University of Guelph, 50 Stone Road E, Guelph, ON, N1G 2W1, Canada
| | - David Kelton
- Ontario Veterinary College, University of Guelph, 50 Stone Road E, Guelph, ON, N1G 2W1, Canada
| | - Zvonimir Poljak
- Ontario Veterinary College, University of Guelph, 50 Stone Road E, Guelph, ON, N1G 2W1, Canada
| | | | | | - Amy L Greer
- Ontario Veterinary College, University of Guelph, 50 Stone Road E, Guelph, ON, N1G 2W1, Canada.
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56
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Gardner EG, Kelton D, Poljak Z, Van Kerkhove M, von Dobschuetz S, Greer AL. A case-crossover analysis of the impact of weather on primary cases of Middle East respiratory syndrome. BMC Infect Dis 2019; 19:113. [PMID: 30717685 PMCID: PMC6362578 DOI: 10.1186/s12879-019-3729-5] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 01/15/2019] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Middle East respiratory syndrome coronavirus (MERS-CoV) is endemic in dromedary camels in the Arabian Peninsula, and zoonotic transmission to people is a sporadic event. In the absence of epidemiological data on the reservoir species, patterns of zoonotic transmission have largely been approximated from primary human cases. This study aimed to identify meteorological factors that may increase the risk of primary MERS infections in humans. METHODS A case-crossover design was used to identify associations between primary MERS cases and preceding weather conditions within the 2-week incubation period in Saudi Arabia using univariable conditional logistic regression. Cases with symptom onset between January 2015 - December 2017 were obtained from a publicly available line list of human MERS cases maintained by the World Health Organization. The complete case dataset (N = 1191) was reduced to approximate the cases most likely to represent spillover transmission from camels (N = 446). Data from meteorological stations closest to the largest city in each province were used to calculate the daily mean, minimum, and maximum temperature (οC), relative humidity (%), wind speed (m/s), and visibility (m). Weather variables were categorized according to strata; temperature and humidity into tertiles, and visibility and wind speed into halves. RESULTS Lowest temperature (Odds Ratio = 1.27; 95% Confidence Interval = 1.04-1.56) and humidity (OR = 1.35; 95% CI = 1.10-1.65) were associated with increased cases 8-10 days later. High visibility was associated with an increased number of cases 7 days later (OR = 1.26; 95% CI = 1.01-1.57), while wind speed also showed statistically significant associations with cases 5-6 days later. CONCLUSIONS Results suggest that primary MERS human cases in Saudi Arabia are more likely to occur when conditions are relatively cold and dry. This is similar to seasonal patterns that have been described for other respiratory diseases in temperate climates. It was hypothesized that low visibility would be positively associated with primary cases of MERS, however the opposite relationship was seen. This may reflect behavioural changes in different weather conditions. This analysis provides key initial evidence of an environmental component contributing to the development of primary MERS-CoV infections.
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Affiliation(s)
- Emma G Gardner
- Ontario Veterinary College, University of Guelph, 50 Stone Road E, Guelph, ON, N1G 2W1, Canada
| | - David Kelton
- Ontario Veterinary College, University of Guelph, 50 Stone Road E, Guelph, ON, N1G 2W1, Canada
| | - Zvonimir Poljak
- Ontario Veterinary College, University of Guelph, 50 Stone Road E, Guelph, ON, N1G 2W1, Canada
| | | | | | - Amy L Greer
- Ontario Veterinary College, University of Guelph, 50 Stone Road E, Guelph, ON, N1G 2W1, Canada.
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Zhou Y, Yang Y, Huang J, Jiang S, Du L. Advances in MERS-CoV Vaccines and Therapeutics Based on the Receptor-Binding Domain. Viruses 2019; 11:v11010060. [PMID: 30646569 PMCID: PMC6357101 DOI: 10.3390/v11010060] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 01/08/2019] [Accepted: 01/10/2019] [Indexed: 12/28/2022] Open
Abstract
Middle East respiratory syndrome (MERS) coronavirus (MERS-CoV) is an infectious virus that was first reported in 2012. The MERS-CoV genome encodes four major structural proteins, among which the spike (S) protein has a key role in viral infection and pathogenesis. The receptor-binding domain (RBD) of the S protein contains a critical neutralizing domain and is an important target for development of MERS vaccines and therapeutics. In this review, we describe the relevant features of the MERS-CoV S-protein RBD, summarize recent advances in the development of MERS-CoV RBD-based vaccines and therapeutic antibodies, and illustrate potential challenges and strategies to further improve their efficacy.
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Affiliation(s)
- Yusen Zhou
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China.
- Institute of Medical and Pharmaceutical Sciences, Zhengzhou University, Zhengzhou 450052, China.
| | - Yang Yang
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA.
| | - Jingwei Huang
- Lindsley F. Kimball Research Institute, New York Blood Center, New York, NY 10065, USA.
| | - Shibo Jiang
- Lindsley F. Kimball Research Institute, New York Blood Center, New York, NY 10065, USA.
| | - Lanying Du
- Lindsley F. Kimball Research Institute, New York Blood Center, New York, NY 10065, USA.
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Bats and Coronaviruses. Viruses 2019; 11:v11010041. [PMID: 30634396 PMCID: PMC6356540 DOI: 10.3390/v11010041] [Citation(s) in RCA: 266] [Impact Index Per Article: 53.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 01/05/2019] [Accepted: 01/07/2019] [Indexed: 11/17/2022] Open
Abstract
Bats are speculated to be reservoirs of several emerging viruses including coronaviruses (CoVs) that cause serious disease in humans and agricultural animals. These include CoVs that cause severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), porcine epidemic diarrhea (PED) and severe acute diarrhea syndrome (SADS). Bats that are naturally infected or experimentally infected do not demonstrate clinical signs of disease. These observations have allowed researchers to speculate that bats are the likely reservoirs or ancestral hosts for several CoVs. In this review, we follow the CoV outbreaks that are speculated to have originated in bats. We review studies that have allowed researchers to identify unique adaptation in bats that may allow them to harbor CoVs without severe disease. We speculate about future studies that are critical to identify how bats can harbor multiple strains of CoVs and factors that enable these viruses to “jump” from bats to other mammals. We hope that this review will enable readers to identify gaps in knowledge that currently exist and initiate a dialogue amongst bat researchers to share resources to overcome present limitations.
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Bak SL, Jun KI, Jung J, Kim JH, Kang CK, Park WB, Kim NJ, Oh MD. An Atypical Case of Middle East Respiratory Syndrome in a Returning Traveler to Korea from Kuwait, 2018. J Korean Med Sci 2018; 33:e348. [PMID: 30595687 PMCID: PMC6306328 DOI: 10.3346/jkms.2018.33.e348] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 11/29/2018] [Indexed: 01/13/2023] Open
Abstract
We report a case of Middle East respiratory syndrome coronavirus (MERS-CoV) infection in a 61-year-old businessman returning from Kuwait. The patient arrived there on August 16, 2018, developed watery diarrhea on August 28 (day 0), and came back to Korea on September 7 (day 10) as his condition worsened. Upon arrival, he complained of diarrhea and weakness, but denied any respiratory symptoms, and he directly went to visit an emergency room. Chest radiography revealed interstitial infiltrates in the lungs, and he was immediately transferred to an isolation unit. Quantitative real-time PCR analysis of sputum samples taken on day 11 returned positive for MERS-CoV. No secondary MERS-CoV infection was identified among people who had close contact with him. This case underscores the importance of a high index of suspicion of MERS-CoV infection in any febrile patients who present after a trip to the Middle East.
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Affiliation(s)
- Song Lee Bak
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Kang Il Jun
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Jongtak Jung
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Jeong-Han Kim
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Chang Kyung Kang
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Wan Beom Park
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Nam-Joong Kim
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Myoung-don Oh
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
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Abstract
The Middle East respiratory syndrome (MERS) is a coronavirus (CoV)-mediated respiratory disease. Virus transmission occurs within health care settings, but cases also appear sporadically in the community. Camels are believed to be the source for community-acquired cases, but most patients do not have camel exposure. Here, we assessed whether camel workers (CWs) with high rates of exposure to camel nasal and oral secretions had evidence of MERS-CoV infection. The results indicate that a high percentage of CWs were positive for virus-specific immune responses but had no history of significant respiratory disease. Thus, a possible explanation for repeated MERS outbreaks is that CWs develop mild or subclinical disease. These CWs then transmit the virus to uninfected individuals, some of whom are highly susceptible, develop severe disease, and are detected as primary MERS cases in the community. Middle East respiratory syndrome (MERS), a highly lethal respiratory disease caused by a novel coronavirus (MERS-CoV), is an emerging disease with high potential for epidemic spread. It has been listed by the WHO and the Coalition for Epidemic Preparedness Innovations (CEPI) as an important target for vaccine development. While initially the majority of MERS cases were hospital acquired, continued emergence of MERS is attributed to community acquisition, with camels likely being the direct or indirect source. However, the majority of patients do not describe camel exposure, making the route of transmission unclear. Here, using sensitive immunological assays and a cohort of camel workers (CWs) with well-documented camel exposure, we show that approximately 50% of camel workers (CWs) in the Kingdom of Saudi Arabia (KSA) and 0% of controls were previously infected. We obtained blood samples from 30 camel herders, truck drivers, and handlers with well-documented camel exposure and from healthy donors, and measured MERS-CoV-specific enzyme-linked immunosorbent assay (ELISA), immunofluorescence assay (IFA), and neutralizing antibody titers, as well as T cell responses. Totals of 16/30 CWs and 0/30 healthy control donors were seropositive by MERS-CoV-specific ELISA and/or neutralizing antibody titer, and an additional four CWs were seronegative but contained virus-specific T cells in their blood. Although virus transmission from CWs has not been formally demonstrated, a possible explanation for repeated MERS outbreaks is that CWs develop mild disease and then transmit the virus to uninfected individuals. Infection of some of these individuals, such as those with comorbidities, results in severe disease and in the episodic appearance of patients with MERS.
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