**4. Pathological changes and clinical diagnosis in SARS-COV infection**

Histopathologic data existing on SARS-CoV patients have been mostly determined from autopsy cases. Pathological lesions in certain organs of SARS-CoV victims, such as the lungs and intestines, have been extensively studied [1, 4]. The primary pathological change in SARS-CoV patients occurs in the lungs [4, 6]. Gross examination of the lungs revealed edematous, heavy lungs weighing up to 2100 g with several areas of extensive consolidation (**Figure 1**) [1, 4].

Histopathologic data for SARS-CoV of infected lungs characteristically displayed diffuse alveolar damage [DAD] [19, 20]. Through the initial period of the disease (7 to 10 days), SARS lungs exhibited the following characteristics of acute exudative DAD: 1) Widespread edema, 2) desquamation of alveolar epithelial cells, 3) formation of hyaline membrane, 4) collapse of alveoli, and 5) fibrous tissue in alveolar spaces (**Figure 2**) [6, 12, 19, 21, 22].

In SARS cases of lengthier disease duration, fibrous organization features of DAD were visible after approximately 10–14 days. These features included interstitial and airspace fibrosis and pneumocytic hyperplasia [12, 23, 24]. The more extensive the disease period, the more widespread the fibrous organization of the lung tissue [14, 25, 26]. Dense septal and alveolar fibrosis were exhibited in SARS cases with duration of more than 2 to 3 weeks [12, 19, 23, 24]. The overall histological data presentation of SARS lung infection is non-specific and dependent on symptom onset; Acute DAD is most frequently associated with early phase disease (<10 days) [6, 27]. Furthermore, there is limited documentation on the pathologic demonstration of SARS-CoV in living patients, since the bulk of patient tissue samples were taken from autopsy [1, 4, 6].

The predominant changes involving SARS-CoV cases have been visceral and involve severe pulmonary changes [1, 19]. Accurate and easily implementable diagnostics formed an essential part of SARS-CoV disease control, due to the nonspecific nature of the infection and its rapid spread. Following the initial disease outbreak, many laboratories rapidly developed SARS-CoV reverse transcription polymerase chain reaction test (RT-PCR) analyzes, to detect viral RNA. These tests have numerous advantages over traditional RT-PCR tests [28].

Real-time RT-PCR assays use amplification primers and internal probes as a result, can be designed to be extremely precise for SARS-CoV RNA [6]. Real-time

**Figure 1.** *SARS gross morphology of the lung [19]. Images ©John Wiley and Sons Ltd. as cited.*

#### **Figure 2.**

*(A) Alveoli filled with desquamated epithelial cells. (B) Formation of hyaline membrane (H&E, original magnification ×200).*

RT-PCR analyzes can be extremely sensitive, with steady detection limits of between 1 and 10 SARS-CoV RNA copies per reaction [6, 29]. They can be completed quicker than traditional RT-PCR analyzes with reduced risk of contamination in the laboratory. Real-time RT-PCR assays often times give a very accurate estimate of the viral load present in a sample [29].

### **5. MERS-CoV**

#### **5.1 Etiology, epidemiology and clinical presentation**

The Middle East respiratory syndrome coronavirus (MERS-CoV or MERS) was first identified in September 2012 in a fatal case of severe respiratory failure in a Saudi Arabian patient [30, 31]. Previous cases were retrospectively acknowledged from an outbreak of severe respiratory illness in Jordan in 2012 [32]. In contrast to the rapid spread and subsequent latency of SARS-CoV, MERS-CoV has moved continuously through the Arabian Peninsula and generated sporadic outbreaks in countries where infected persons have traveled [6]. As of January 2020, there have been 2519 laboratory-confirmed cases of MERS, and 866 associated deaths (casefatality rate: 34.3%) reported globally [32].

A significant number of cases has been identified in Saudi Arabia and to a lesser extent the United Arab Emirates (UAE), Qatar and Jordan [33]. While the close relationship to numerous bat coronaviruses suggests a bat-related origin, overwhelming molecular and serological evidence points to the involvement of dromedary camels in the transmission of MERS-CoV to a human host [34]. While transmission from ancestral bats to camels cannot be excluded, and camels may have introduced the virus into human populations, the majority of reported MERS-CoV cases have ensued from human-to-human nosocomial transmission [6, 33].

A hospital outbreak was reported in Saudi Arabia with a cluster of six cases; Three of the cases were healthcare workers, two were patients (one of whom died) and one was a visitor. Another instance involved an ill patient admitted to a Korean *Severe Acute Respiratory Syndromes and Coronaviruses (SARS-CoV, MERS-CoV… DOI: http://dx.doi.org/10.5772/intechopen.97564*

hospital which led to an outbreak of 186 infections including 36 fatal cases [35]. Person-to-person transmission has also been identified within households, where the highest risk of transmission involves patient respiratory secretions and individuals being within close proximity with each other. Individuals exhibiting signs and symptoms or other epidemiological characteristics suggestive of MERS should be promptly quarantined and tested for viral infection [32, 35].
