**6. MERS-CoV infection in humans**

The clinical manifestation for MERS-CoV infection varies from asymptomatic/ mild to severe disease. Generally, individuals with chronic comorbid conditions (diabetes, heart disease) and elderly patients are at increased risk for development of respiratory failure [35]. Although infection is commonly associated with respiratory disease, in some rare cases viral RNA has been discovered in blood, stool and urine signifying a systemic infection [33, 35].

Notwithstanding the increased mortality related to symptomatic cases, research studies have shown that roughly 25% of patients infected with MES-CoV are asymptomatic [36]. A seroepidemiological analysis of over 10,000 infected samples from Saudi Arabia revealed positive antibodies in approximately 0.15% of patients. Individuals with some level of camel-exposure had an increased likelihood of positive serology [33, 35]. Clinical symptoms are non-specific, and patients have reported an expansive range of diverse indicators including chest pain, fever, cough, myalgia, sore throat, shortness of breath, vomiting and diarrhea [32]. In more severe cases, mechanical ventilation is required for patients who are presented with acute hypoxic respiratory failure [15, 31]. Fatal outcome of MERS-CoV infection have been associated with underlying comorbidities such as hypertension, diabetes mellitus type II, obesity, and cardiac disease [37]. MERS-CoV infection has an incubation period that ranges from 2 to 14 days [30]. Signs and symptoms usually appear well before the patient reaches a detectable viremia i.e. the virus is present in the patients' bloodstream [30, 37]. Neurological sequelae, and gastrointestinal distress have also been documented in addition to these respiratory symptoms [37].
