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Coronaviruses are a large family of RNA viruses that may cause illness in animals or humans. Seven known coronaviruses cause human infections. Three are highly pathogenic. These include SARS, Middle East respiratory syndrome (MERS), and the recently discovered coronavirus, SARS‐CoV2 (2019‐nCoV), which causes the disease COVID‐19. Each has generated a large‐scale public health response. In humans, these coronaviruses typically manifest as respiratory infections ranging from mild symptoms to more severe presentations leading to pneumonia, acute respiratory distress syndrome, respiratory failure, and death. Zoonotic transmission to humans likely occurs from civet cats (SARS), dromedary camels (MERS), and bats (SARS‐CoV2).

It is difficult to distinguish coronavirus infections from other respiratory infections because patients present with symptoms similar to those of other febrile respiratory illnesses [18, 19]. Fever is the most common and earliest symptom of coronavirus infection, often accompanied by headache, malaise, or myalgia. Among patients with coronavirus infection, high fever, diarrhea, and vomiting are more common when compared with patients with other respiratory illnesses [20]. Cough occurs later in the course of disease and patients are less likely to have rhinorrhea or sore throat as compared to other lower respiratory tract illnesses [21]. The virus is typically found in respiratory secretions but can also be isolated in other body fluids such as urine and fecal matter. Transmission is typically via droplet spread from respiratory secretions. Thus, intubation and procedures that aerosolize respiratory secretions pose high risk. Since clinical features alone cannot reliably distinguish coronavirus infections from other respiratory illnesses, knowledge of contacts is essential [22]. Potential contact with patients known to have coronavirus infection, contact within coronavirus‐affected areas, or linkage to a cluster of pneumonia cases should be obtained in the history [23]. Development of effective drug therapies and vaccines specifically for coronavirus infections is the subject of a global effort in light of the SARS‐CoV2 pandemic.

The first coronavirus infection was recognized as a global threat in mid‐March 2003 due to outbreaks in Toronto Canada, Singapore, Vietnam, Taiwan, and China [24]. The first of these known cases of SARS occurred in Guangdong province, China, in November 2002 [25, 26]. The World Health Organization reported the last human chain of transmission of SARS to be broken in July 2003. The case‐fatality rate for SARS is approximately 8%, usually due to respiratory failure. The case‐fatality rate is less than 1% for SARS patients younger than 24 years and up to 50% for those 65 years and older or those with comorbid illness [27]. There are no confirmed cases of transmission from asymptomatic cases. There have not been any cases of SARS infections anywhere in the world since a 2004 outbreak in China, where two researchers contracted SARS while working in a virology institute where experiments using live and inactivated SARS coronavirus were carried out [28].

A second novel coronavirus related to SARS, MERS‐CoV, emerged in 2012. The origins of the virus are not fully understood, but according to the analysis of different virus genomes it is believed to have originated in bats and later transmitted to camels at some point. MERS‐CoV is transferred to humans from infected dromedary camels through direct or indirect contact. Human‐to‐human transmission is possible, but only a few such transmissions have been found among family members living in the same household. In health care settings, human‐to‐human transmission appears to be more frequent. However, the virus has not been shown to spread in a sustained way. MERS‐CoV has been identified in several countries in the Middle East, Africa, South Asia, and the United States. In total, 27 countries have reported 2562 cases since the virus's initial discovery in 2012, including the latest outbreak in Saudi Arabia in 2020. There have been 881 known deaths due to the infection and related complications.

On December 31, 2019, the Medical Administration of Wuhan Municipal Health Committee in Hubei Province, China issued an urgent notice regarding patients requiring hospitalization due to pneumonia of unknown cause. Of the 27 cases, seven were critically ill. Health officials determined that one or more patients had been in a local seafood market prior to becoming ill. Chinese officials notified the World Health Organization of this cluster on January 3, 2020, and 6 days later reported the outbreak was due to a newly identified coronavirus. The viral genetic sequence was published two days later, and the first reported case of this novel coronavirus outside China was identified on January 13, 2020. Within less than 2 weeks, the virus was identified in patients in several countries in Asia, Western Europe, and the United States. By January 30, the World Health Organization declared the novel coronavirus, SARS‐CoV2, a public health emergency of international concern.

The disease resulting from SARS‐CoV2 infection was termed coronavirus infectious disease 2019 (COVID‐19). The average incubation period ranges from 2 to 12 days, with a median of 5‐6 days. The most common symptoms of COVID‐19 are fever, dry cough, and tiredness. Other symptoms that are less common and may affect some patients include aches and pains, nasal congestion, headache, conjunctivitis, sore throat, diarrhea, loss of taste or smell, a rash on the skin, and discoloration of fingers or toes. These symptoms are usually mild and begin gradually. Some people who become infected may have very mild or no symptoms. The diagnosis can be suspected on clinical grounds and confirmed by viral testing that detects viral RNA.

The virus is spread primarily from person to person through small droplets from the nose or mouth, when a person with COVID‐19 coughs, sneezes, or speaks. The droplets can also land on objects and surfaces, be picked up by contact with these objects or surfaces, and become infective when one's eyes, nose, or mouth are touched. Asymptomatic spread of the virus from person to person may also occur.

The majority of people with COVID‐19 experience mild to moderate respiratory illness and recover without requiring special treatment. Older people, and those with underlying medical problems like cardiovascular disease, diabetes, chronic respiratory disease, and cancer are more likely to develop serious illness. Overall mortality for COVID‐19 infection is approximately 2.2%. Table 23.3 compares the burden of disease related to coronavirus infections with influenza outbreaks.

Several therapeutic agents have been evaluated for the treatment of COVID‐19. Remdesivir, an inhibitor of the viral RNA‐dependent RNA polymerase known to be effective against SARS and MERS, may also be effective in treatment of COVID‐19 [29–31]. Given the global nature of this pandemic, major efforts at developing vaccines have resulted in a number of vaccines now being available [32].

If coronavirus infection is suspected, EMS clinicians must follow all routine practices and some additional precautions [33]. This includes an initial assessment for any signs or symptoms of a respiratory infection or potential coronavirus risk factors. The initial assessment should be done from distance of at least 2 meters (6 feet) from the patient, if possible. Patient contact should be minimized, to the extent possible, until PPE is in place and a facemask is on the patient. EMS systems may also elect to limit or avoid any procedures that may increase risk to EMS personnel. These include tracheal intubation, deep suctioning, use of non‐invasive ventilatory support (continuous or bi‐level positive airway pressure), administration of nebulized medication, and any other procedure that may aerosolize respiratory secretions. During the SARS outbreaks, paramedics did not perform aerosol‐generating medical procedures in the prehospital setting to limit possible disease transmission [34]. If an aerosol‐generating medical procedure is anticipated, personnel should use N95 respirators as part of their PPE. Oxygen masks, bag‐valve‐mask ventilators, and other respiratory or ventilatory equipment should be equipped to filter expired air. Finally, EMS personnel and systems should notify the receiving facility of a patient suspected of coronavirus, permitting hospital staff to have appropriate PPE in place and a suitable isolation room prepared for the patient [35, 36].

Table 23.3 Comparison of coronavirus infections, seasonal influenza, and 1918 pandemic influenza

	SARS	MERS	COVID‐19a	Seasonal influenza (annual)	1918 pandemic influenza
R0b	3	1.9‐3.9	1.95‐3.28	0.9‐2.1	1.4‐2.8
Total cases	8906	2562	131,909,792	1 billion	500 million
Deaths	744	881	2,854,276	389,000	50 million
Case fatality rate (%)	8.4	34.4	2.2	0.04	10

^a As of April 5, 2021 [63].

^b Basic reproduction number: number of new cases that can develop from one confirmed case.Sources: From [62–67].