**9. SARS-CoV-2 infection in humans**

SARS-CoV-2 infections are variable in nature, with some infections being asymptomatic with others causing minor to moderate illness with respiratory and flu-like symptoms, including sore throat, fever, chills, and cough [53]. Injury, inflammation and ensuing respiratory distress in SARS-CoV-2 patients occurs as a result of the SARS-CoV-2 spike protein binding to human angiotensin I-converting enzyme 2 (hACE2) predominantly targeting the virus to type II pneumocytes inside the lung [54, 55]. A substantial number (approximately 20%) of patients also develop severe infection and multi-organ failure which necessitates intensive care with mechanical ventilation or extracorporeal membrane oxygenation [50, 53]. In some cases, SARS-Cov-2 infection can be deadly, with a case fatality rate of ~5%. The incubation period of SARS-CoV-2 is generally 5–7 days, but the symptoms of infection may present itself well after that period [56]. The phase from the onset of symptoms to fatality usually varies from 7 to 40 days with a median of 14 days [57]. This phase is dependent on the patients' age, and the status of their immune system.

Similarities in the symptoms between SARS-CoV-2 and earlier beta-coronavirus such as fever, dry cough, and dyspnea are distinctive [50]. However, there are distinctive features presented by SARS-CoV-2 which involves affecting of the lower airway as evident by upper respiratory tract indicators like sneezing, rhinorrhoea, and sore throat [58]. Additionally, chest radiograph results taken upon admission, show an infiltrate in the upper lobe of the infected lungs, associated with increased difficulty breathing (dyspnea) resulting in low levels of oxygen in the blood (hypoxemia) [58]. Notably, while most SARS-CoV-2 patients exhibit gastrointestinal symptoms like diarrhea, very few MERS-CoV or SARS-CoV patients show similar gastrointestinal concerns. Thus, testing fecal and urine samples to exclude a potential alternative route of transmission among patients and healthcare workers [57].
