Coronaviruses (CoV) are a large viral family, known since the mid-1960s, that cause respiratory infections in humans and animals. Generally, coronavirus infections cause mild to moderate respiratory illnesses, similar to the common cold. Most people become infected with common coronaviruses throughout their lives, with young children being more susceptible to infection. The common coronaviruses that infect humans are alpha coronaviruses 229E and NL63 and beta coronaviruses OC43, HKU1.
Some coronaviruses can cause severe respiratory syndromes, such as the severe acute respiratory syndrome known by the acronym SARS from the English term “Severe Acute Respiratory Syndrome.” SARS is caused by the coronavirus associated with SARS (SARS-CoV), with the first reports in China in 2002. SARS-CoV spread rapidly to more than twelve countries in North America, South America, Europe, and Asia, infecting over 8,000 people and causing around 800 deaths before the global SARS epidemic was controlled in 2003. Since 2004, no cases of SARS have been reported worldwide.
In 2012, another new coronavirus was isolated, distinct from the one that caused SARS in the early last decade. This new coronavirus was unknown as a human disease agent until its identification, initially in Saudi Arabia and later in other countries in the Middle East, Europe, and Africa. All identified cases outside the Arabian Peninsula had a history of travel or recent contact with travelers from Middle Eastern countries – Saudi Arabia, Qatar, United Arab Emirates, and Jordan.
Due to the location of the cases, the disease began to be designated as Middle East respiratory syndrome, abbreviated as MERS, from the English term “Middle East Respiratory Syndrome,” and the new virus named coronavirus associated with MERS.
Clinical Manifestations
Common human coronaviruses cause mild to moderate short-lived respiratory infections. Symptoms may include runny nose, cough, sore throat, and fever. These viruses can sometimes cause lower respiratory tract infections, such as pneumonia. This condition is more common in people with cardiopulmonary diseases, compromised immune systems, or in the elderly.
MERS-CoV, like SARS-CoV, causes severe infections.
• Incubation Period: 2 to 14 days
• Period of Transmissibility: In general, viral transmission occurs only while symptoms persist. Viral transmission may be possible after symptom resolution, but the duration of the transmissibility period is unknown for SARS-CoV and MERS-CoV. During the incubation period and in asymptomatic cases, individuals are not contagious.
• Human-to-Human Transmission: All coronaviruses are transmitted from person to person, including SARS-CoV, but without sustained transmission. Regarding MERS-CoV, the WHO considers that there is currently well-documented evidence of person-to-person transmission, but no evidence of sustained transmission occurring.
• Mode of Transmission: In general, the main mode of transmission of coronaviruses occurs through close contact* from person to person.
* Definition of close contact: Any person who cared for the patient, including health professionals or family members; who had physical contact or remained in the same location as the sick patient.
• Source of Infection: Most coronaviruses infect only one animal species or, at least, a small number of closely related species. However, some coronaviruses, such as SARS-CoV, can infect both people and animals. The animal reservoir for SARS-CoV is uncertain, but it appears to be related to bats. There is also the possibility of an animal reservoir for MERS-CoV that has been isolated from camels and bats.