Is COVID-19 a serious concern, or are we overreacting? PNWU scientists offer expert insight into the severity of COVID-19.
At this time, we can’t predict how severe COVID-19 might be when someone tests positive. COVID-19 is a global pandemic, but its effects on individual people, municipalities, and even nations are quite variable. With most infectious diseases, people come to medical attention because of symptoms, as was the case originally in Wuhan, China. There, scores of people developed fever, cough, and difficulty breathing in a few weeks, and did not respond well to the usual antibiotic treatment. The genetic code of the virus was quickly determined and communicated, which made diagnosis much easier, faster, and cheaper. This made it possible to study large populations for the virus, including asymptomatic people.
The severity of COVID-19 can be classified by increasing probability of death.
Some people infected with the virus have no symptoms. They feel fine, and apparently do not develop major illness. The proportion of such people varies widely across large studies. The numbers may be as high as 88%. However, data shows that asymptomatic people may produce as much infectious virus as those that show symptoms. These people can easily transmit the virus to others, because they don’t know they have it and may be less cautious around others. The proportion of such people in Yakima is unknown, because large scale testing has not been done here.
Some people carry the virus, usually in their nose or mouth, for up to 2 weeks before they become ill. Typically, they develop a fever, cough, and shortness of breath. These people are most infectious from 3 days before they become sick up until a week into their illness. Some studies show that such people account for 10% of the infected population. Again, the proportion of such people in Yakima is unknown, because testing here has focused mostly on people with symptoms.
This is the situation in most recorded cases: the person becomes ill, usually with fever, cough, and shortness of breath, and then tests positive for the virus. Some lucky people, like Tom Hanks, suffer only mild symptoms. These are usually younger people and those without medical conditions like high blood pressure, diabetes, heart disease, or kidney problems. They usually recover in 2-3 weeks without needing additional oxygen or being admitted to the hospital. The proportion of people infected with COVID-19 who are ill, but do not require hospitalization varies between 50-90%, depending on location, age, and additional medical conditions. Most of the ~7,000 people who recently tested positive for the virus in Yakima County fit into this category of severity.
Low Blood Oxygen Levels (Hypoxia)
More severely ill patients, such as British Prime Minister Boris Johnson, can develop severe lung damage. This can lower blood oxygen levels and cause organ damage. Organs such as the brain, heart, kidneys and limbs (arms, legs, fingers, and toes) are particularly vulnerable to damage if the blood oxygen levels are low. Such patients are routinely hospitalized. They receive oxygen, usually first into the nose, but sometimes higher concentrations are given by face masks. Recent data from Yakima County indicate that about 7.6% of people who tested positive for the virus required hospitalization.
When other sources of oxygen cannot provide enough oxygen to stop organ damage and organ failure, a plastic tube is inserted through the nose or mouth into the trachea and attached to a machine called a ventilator. The ventilator takes over normal breathing function. After intubation and ventilation is required, COVID-19 has a high death rate, even compared to other viral pneumonias like influenza. Because of the risk of potential complications, patients on a ventilator are usually transferred to intensive care units (ICU). About 23% of recent patients hospitalized for COVID-19 in Yakima required mechanical ventilation.
The risk of death from COVID-19 increases with the patient’s age, and the number and type of pre-existing medical conditions. For example, 120 of the 127 recent deaths from COVID-19 in Yakima occurred in people with underlying health conditions. The risk of death among those who tested positive for the virus in Yakima County increased from 3% among 60-69-year-olds, to 12% among 70-79-year-olds, to 19% in those over age 80 years.
In a Nutshell
Even with the information that we currently have, it is still impossible to predict the ultimate severity of COVID-19 after a person tests positive.
Written by William Elliott, M.D., Ph.D., Kimberly Taylor, Ph.D., Albert Brady, M.D., and Julie Randolph-Habecker, Ph.D.