Infectious diseases | Respiratory | COVID-19

COVID-19 is caused by the virus SARS-CoV-2. Discovery of this contagious disease was first reported near the end of 2019. Since early 2020, COVID-19 has spread worldwide to become the first viral pandemic in more than 100 years.

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COVID-19 is a viral infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). SARS-CoV-2, a virus of the Coronaviridae family, is defined by its large single-stranded RNA genome and its very high level of transmission and disease-causing pathology. In contrast to SARS-CoV-2, several other human coronaviruses are among the frequent viral causes of the common cold. 


The name coronavirus is derived from the Latin word corona, meaning “crown” or “wreath”, features of which characteristically appear upon observation of coronavirus virions utilizing electron microscopy. The spike proteins, which are readily present on the surfaces of coronaviruses, are largely responsible for defining this crown-like morphology.


SARS-CoV-2 was first identified in Wuhan, China in November 2019. Just prior to declaring the pandemic nature and worldwide public health emergency due to the spread of the virus, the World Health Organization (WHO) announced “COVID-19” as the new disease that is caused by SARS-CoV-2 infection. The term COVID-19 is derived from the abbreviation of coronavirus disease of 2019.


COVID-19 is primarily a disease of the respiratory tract and may present a wide range of disease severity, including:


  • Little to no symptoms
  • Mild symptoms
  • Severe pneumonia
  • Acute respiratory distress syndrome (ARDS)


Symptoms commonly occur within 2 to 14 days after exposure to the virus and include:


  • Fever

  • Shaking chills

  • Cough

  • Shortness of breath

  • Fatigue

  • Muscle aches

  • Loss of smell and taste


Children generally have milder illness compared to illness experienced by adults, but the symptoms are often similar between the two groups. 


The elderly, individuals with hypertension and heart disease, and individuals with underlying immunocompromise are significantly more susceptible to severe disease, which may include: 


  • Hypoxia

  • Pneumonia

  • ARDS

  • Multiorgan failure

  • Septic shock

  • Thrombotic events

  • Death


Since the initial outbreak in late 2019, the WHO has confirmed hundreds of millions of reported infections attributed to SARS-CoV-2, with millions of reported deaths attributed to COVID-19 worldwide.

SARS-CoV-2 is highly contagious and very easily transmitted via aerosols from person-to-person when in close contact with one another (e.g., within six feet of distance). When an infected individual speaks, coughs or sneezes, the virus is released into the air in the form of tiny droplets, which other individuals can breathe in and contract infection. COVID-19 is primarily spread by infected individuals with symptoms; however, disease may also be spread by individuals who are asymptomatic. A less common method of transmission occurs when individuals touch surfaces contaminated with the virus and then touch their faces, thus exposing themselves to viral infection via the respiratory tract.

While there is no absolute method of fully preventing the contraction of COVID-19, there are several recommended ways to help prevent the spread of disease and severe illness.

Staying up to date on receiving the latest COVID-19 vaccines helps protect from severe illness. Research has shown that receipt of two initial shots against SARS-CoV-2 followed up with a booster shot against SARS-CoV-2 is approximately 70 percent effective in preventing severe disease and hospitalization. 

Social distancing also helps prevent the spread of disease, and includes:

  • Maintaining a distance of six feet or more from other people 

  • Avoiding groups, crowded places and mass gatherings

  • Moving activities outdoors for more open space  

Adherence to basic health and hygiene is another way to help prevent or limit the spread of disease. Washing hands frequently with soap and water for at least 20 seconds, especially after being in public places, can help prevent spreading the virus. If soap and water are not available, using a hand sanitizer that contains at least 60 percent alcohol can also be effective in removing coronavirus germs. Touching the eyes, nose or mouth with unwashed hands can commonly permit the virus to enter the respiratory system.

Correctly wearing a well-fitting facemask or respirator in indoor public spaces such as airports and public transit areas can help prevent the spreading of the virus. Individuals working in hospitals or long-term care facilities where disease spreads easily should wear a mask at work. 

A combination of vaccination, social distancing, maintenance of basic hygiene, such as hand washing, and wearing a mask provides the best protection from the virus, which is continuously prone to evolutionary mutation. Individuals of all ages with underlying medical conditions, particularly if not well controlled, as well as individuals who are at higher risk may want to continue taking preventative precautions. Those at higher risk for severe illness include individuals:

  • Aged 65 years and older 

  • Residing in nursing homes or long-term care facilities

  • Residing or working in areas with high-risk patients 

  • Suffering from serious heart conditions

  • With chronic lung disease or moderate to severe asthma 

  • With immune systems that are compromised in some way (i.e., immunocompromised), such as from cancer, frequent smoking, bone marrow or organ transplantation, or overall immune deficiencies

  • With severe obesity (i.e., body mass index of 40 or higher) 

  • With diabetes

  • With chronic kidney disease undergoing dialysis

Clinicians are not able to accurately diagnose coronavirus based on signs and symptoms alone. There currently are two main types of tests that are typically used for the detection of SARS-CoV-2. Reverse transcription polymerase chain reaction (RT-PCR), a molecular technique that utilizes primers and probes that are highly specific for certain gene targets, is usually the most accurate method to detect the presence of SARS-CoV-2 viral RNA in human respiratory samples. Detection of viral pathogens utilizing molecular techniques is increasingly replacing viral cell culture as the gold standard method for definitive confirmation or diagnosis.

Rapid antigen testing, frequently in the form of lateral flow immunoassays, is another method commonly used for detecting the virus in respiratory samples. While usually less sensitive than molecular detection methods, antigen tests have the advantage of being very fast to perform (e.g., final results in 15 minutes or less) and also very easy to perform (i.e., requiring no specialized training to operate). Antigen tests are also well-suited to be operated not only in acute care settings, but also often at the site where patient care takes place (i.e., the point of care), such as in the physicians’ offices, urgent care settings, pharmacies, or even at home. These tests offer the advantage of quickly identifying infection at the point of care, effectively enabling health systems to proactively treat, and in some cases isolate, individuals early in the course of disease.

Treatment for COVID-19 includes antiviral medications that help reduce the severity of the disease. Some individuals, with mild to moderate symptoms, particularly those with underlying health risks, are recommended to start treatment within the first five days of symptoms. Therefore, it is important to seek medical care upon the onset of symptoms. Antiviral treatments are prescribed by a doctor, and include:

  • Ritonavir-boosted nirmatrelvir tablets

  • Remdesivir IV infusion

  • Molnupiravir capsules

There are multiple, ongoing clinical studies that seek to learn more about SARS-CoV-2 and how it affects the major systems of the body in order to develop more effective preventions and treatments.

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