The most common presenting symptoms of COVID-19 illness are fever, dry cough, shortness of breath and other common viral symptoms such as sore throat. The fever is very common, occurring in 88% of patients. But a small number of patients don’t present with fever and health professionals need to be aware of that. About 65% of patients have dry cough. The symptoms usually start about 5 days after exposure to the virus. This is called the incubation period. But the incubation period can be as long as 11 days. That is why the isolation of contact cases is 14 days.
Runny nose occurs only in 5% of patients. Recall in my post about immunity that the SARS-CoV-2 virus can escape detection by innate immunity. The innate immunity involves the initial barrier to viral infections. The symptoms are runny nose, runny eyes, sinus drainage, all are attempts at preventing the virus from entering the human body and reducing the viral load. This virus is able to escape that.
About 10 percent of patients can present with GI symptoms of diarrhea, nausea and vomiting causing dehydration. The ACE-2 protein widely prevalent in the lung which is a target of binding of the spike protein of the virus is also present in the GI tract.
More than 85% of patients develop only mild symptoms and don’t progress to pneumonia but 15% do get sick. The most uncomfortable symptom of those who become severely afflicted is shortness of breath. The oxygen tensions go down. And patients may not be initially aware of this. You can buy a simple pulse oximetry (about $20-40 in your local pharmacy) and check your oxygenation. Expect the number to be above 95%. Any number below 90% is not good.
About half of those are sick enough to require significant oxygen support and even mechanical ventilation. Those patients can also develop heart attacks, kidney failure and septic shock.