Asymptomatic carrier state, acute respiratory disease, and pneumonia due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2): Facts and myths

J Microbiol Immunol Infect. 2020 Jun;53(3):404-412. doi: 10.1016/j.jmii.2020.02.012. Epub 2020 Mar 4.


Since the emergence of coronavirus disease 2019 (COVID-19) (formerly known as the 2019 novel coronavirus [2019-nCoV]) in Wuhan, China in December 2019, which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), more than 75,000 cases have been reported in 32 countries/regions, resulting in more than 2000 deaths worldwide. Despite the fact that most COVID-19 cases and mortalities were reported in China, the WHO has declared this outbreak as the sixth public health emergency of international concern. The COVID-19 can present as an asymptomatic carrier state, acute respiratory disease, and pneumonia. Adults represent the population with the highest infection rate; however, neonates, children, and elderly patients can also be infected by SARS-CoV-2. In addition, nosocomial infection of hospitalized patients and healthcare workers, and viral transmission from asymptomatic carriers are possible. The most common finding on chest imaging among patients with pneumonia was ground-glass opacity with bilateral involvement. Severe cases are more likely to be older patients with underlying comorbidities compared to mild cases. Indeed, age and disease severity may be correlated with the outcomes of COVID-19. To date, effective treatment is lacking; however, clinical trials investigating the efficacy of several agents, including remdesivir and chloroquine, are underway in China. Currently, effective infection control intervention is the only way to prevent the spread of SARS-CoV-2.

Keywords: 2019-nCoV; Acute respiratory disease; Asymptomatic carrier; COVID-19; Coronavirus; SARS-CoV-2; Wuhan pneumonia.

Publication types

  • Review

MeSH terms

  • Adenosine Monophosphate / analogs & derivatives
  • Adenosine Monophosphate / therapeutic use
  • Adolescent
  • Adult
  • Aged
  • Alanine / analogs & derivatives
  • Alanine / therapeutic use
  • Asymptomatic Infections / epidemiology*
  • Betacoronavirus
  • COVID-19
  • China / epidemiology
  • Chloroquine / therapeutic use
  • Comorbidity
  • Coronavirus Infections / epidemiology*
  • Coronavirus Infections / pathology
  • Humans
  • Infection Control / methods*
  • Middle Aged
  • Pandemics / prevention & control*
  • Pneumonia, Viral / epidemiology*
  • Pneumonia, Viral / pathology
  • SARS-CoV-2
  • Young Adult


  • remdesivir
  • Adenosine Monophosphate
  • Chloroquine
  • Alanine