Symptoms of COVID-19: A Review of Studies

Symptoms of COVID-19: A Review of Studies

The signs and symptoms of COVID-19 vary from person to person. An exploratory study indexed on PubMed explained that the clinical spectrum of this disease ranges from asymptomatic to severe. Some cases involved mild symptoms, while others necessitate serious medical attention. Nonetheless, this article provides a definitive guide to the clinical presentation or symptoms of COVID-19 based on the available literature.

2019 Coronavirus Disease Clinical Presentation: The Sign and Symptoms of COVID-19 According to Studies

Three Major Trajectories of the Disease

A primer for emergency physicians published in The American Journal of Emergency Medicine identified and described the three major trajectories of COVID-19. These are mild disease with upper respiratory symptoms, non-severe pneumonia, and severe pneumonia complicated by acute respiratory distress syndrome or ARDS.

Upper respiratory symptoms are similar to other viral upper respiratory illnesses caused by influenza or other strains of the coronavirus. These include fever, dry or productive cough, fatigue, and dyspnea or labored breathing. Other symptoms include sore throat, muscle aches, and nasal congestion or runny nose.

Patients with non-severe pneumonia will experience similar upper respiratory symptoms but with a higher degree of severity. Note that pneumonia is an inflammation of the air sacs or alveoli due to infection, thus, in the case of COVID019, is an indicator that the SARS-CoV-2 virus has already affected the lower respiratory system.

Severe pneumonia complicated by ARDS is a critical respiratory failure characterized by widespread inflammation in the lungs and the occurrence of fluid build up in the alveoli. Severe shortness of breath is the main symptom of ARDS. Other symptoms include labored breathing, low blood pressure, bluish skin color, extreme fatigue, and confusion.

Note that the disease also causes damages to the different tissues and organs of the body because it infects cells outside the respiratory system. Infection to other sites could also trigger a phenomenon called cytokine storm in which the immune system goes on an overdrive by releasing excessive amounts of cytokines, which in turn, activates large amount of immune cells, and cause systemic inflammation.

Diarrhea and Other Digestive Symptoms of COVID-19

There is a growing body of anecdotal evidence and observational data indicating the manifestation of digestive or gastrointestinal problems among a considerable portion of COVID-19 patients. A review study by Chinese researchers reported that these symptoms include diarrhea, nausea, vomiting, and abdominal pain.

Stool specimens from infected patients demonstrated traces of SARS-CoV-2 RNA. The viral receptor angiotensin-converting enzyme 2 or ACE2 was highly expressed in gastrointestinal epithelial cells of patients. These findings suggest that the novel coronavirus can actively infect and replicate in the gastrointestinal tract.

Another study published in The American Journal of Gastroenterology further revealed that patients with digestive problems usually had a longer gap between the onset of symptoms and hospitalization than those presenting only respiratory symptoms. Patients with respiratory symptoms were more likely to be cured than those with digestive problems.

The same study mentioned above indicated that COVID-19 patients with gastrointestinal symptoms had a poor clinical outcome and a higher risk of death compared to those who did not experience these symptoms. Hence, it recommends the need to raise the index of suspicion in at-risk patients with gastrointestinal symptoms.

Loss of Smell and Taste as Possible Indicators

A bulletin published online by the American Academy of Otolaryngology-Head and Neck Surgery acknowledged the growing anecdotal reports indicating that the loss of smell or anosmia and distortion of the sense of taste or dysgeusia could be significant COVID-19 symptoms. The organization proposed the inclusion of these two in screening considerations.

The Journal of the American Medical Association published a case study involving a patient whose main symptom was a sudden and complete loss of smell. The patient had previously developed a dry cough but with no fever.

Preliminary findings by a team of researchers at Harvard Medical School identified several cell types in the nasal cavity that are vulnerable to SARS-CoV-2 infection. Essentially, certain cells in the nose express genes that could facilitate infection, thus possibly explaining why some COVID-19 patients develop anosmia.

Another preliminary study by Cristina Menni et al. analyzed data from a tracker app and showed that 59 percent of COVID-19 patients reported a loss of smell and taste. It also showed that a combination of loss of smell and taste, fever, persistent cough, fatigue, diarrhea, abdominal pain, and loss of appetite is predictive of a COVID-19 positive test.

Eye Pain Due to Conjunctivitis or Pink Eye

There is also an emerging body of anecdotal reports and studies suggesting eye conjunctivitis or pink eye as a symptom of COVID-19. A study appearing in the New England Journal of Medicine found that 9 out of 1099 individuals across mainland China who tested for SARS-CoV-2 had pink eye due to conjunctival congestion.

Another study published in the Journal of Medical Virology investigated 30 COVID-19 patients and found that one had conjunctivitis. An analysis of the tears and conjunctival secretion of this patient via RT-PCR testing revealed the presence of SARS-CoV-2. Hence, an eye infection is possible, and the ocular route is a potential infection source.

In another study appearing in JAMA Ophthalmology, 12 out of 38 COVID-19 patients from Hubei Province in China had ocular manifestations, such as epiphora, conjunctival congestion, or chemosis. Furthermore, these manifestations seem to commonly occur in patients with more severe cases of the disease or systemic manifestations.

The presence of the novel coronavirus in eye secretions of individuals with COVID-19 and conjunctivitis essentially suggest that the virus can invade the conjunctiva, while also providing another mode of transmission. Essentially, an infected individual can spread the virus if he or she rubs his or her eyes and touches someone else.


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