Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and Modes of Transmission

SARS‑CoV‑2 is a zoonotic human coronavirus (CoV) closely related to those coronaviruses that previously caused severe acute respiratory syndrome (SARS‑CoV) and Middle East respiratory syndrome (MERS‑CoV).¹⁸ Coronaviruses have a lipoprotein envelope with spinous processes that resemble a crown (corona).¹⁹ Coronaviruses that circulate among humans are usually benign and cause about a quarter of “common cold” illnesses.²⁰ Today and starting in 2019, a severe infection associated with a coronavirus, COVID‑19, has emerged. This is a new, or novel, illness caused by a previously unknown coronavirus, SARS‑CoV‑2. It is postulated that SARS‑CoV‑2 emerged into the human population through an initial zoonotic virus that was infecting bats, which are a natural animal reservoir. This virus may have mutated and ultimately started causing disease in humans. Due to the novel nature of the SARS‑CoV‑2 virus, the long incubation period and worldwide spread, and the rapid development of treatments and vaccinations, the overall infection rate, mortality rate, and other statistics are, as of yet, unknown.

Modes of transmission for SARS‑CoV‑2 include contact, droplet, airborne, fomite, fecal-oral, bloodborne, mother-to-child, and animal-to-human transmission.²¹ Infection with SARS‑CoV‑2 primarily causes respiratory illness ranging from mild disease to severe disease and death, and some people infected with the virus never develop symptoms.²¹