**1. Introduction**

Coronavirus (CoV) is one of the leading pathogens primarily targeting that the human respiratory system [1]. Earlier outbreaks of coronaviruses include the severe acute respiratory syndrome (SARS)-CoV and the Middle East respiratory syndrome (MERS)-CoV which have been formerly considered as a serious threat to public health [2]. The first iteration of coronavirus was identified in the mid-1960s and categorized into four separate subfamilies: α−/β−/γ−/δ-Coronavirus. Alpha and beta-coronaviruses predominantly causes infection in mammals, whereas gamma and delta-coronaviruses primarily infect birds [3]. A new contagious coronavirus is presently holding much of the worldwide population hostage. This virus,

SARS-CoV-2, which causes the COVID-19 disease, emerged in Hubei, China and has spread to most countries with ongoing devastating effects [4].

Since the era of the pneumonic plague, emergent respiratory infections have enthralled the scientific and Public communities' and more recently have manifested in popular films depicting airborne viral outbreaks [5]. This has led to deliberations pertaining to the possibility for respiratory spread of these infections [6]. Although numerous emerging agents can exhibit respiratory involvement, this chapter will focus on emerging pathogens that involve the respiratory system and focus on 3 agents that exhibit a range of characteristics of emerging diseases: SARS-CoV, MERS, and SARS-CoV-2.
