The powerful symptoms and many manifestations of COVID-19 are complicating efforts to treat the disease and stop its spread.
The panorama: There are very few illnesses that everyone experiences the same. But COVID-19 disease patterns are unusual compared to other recent pandemics, and it could usher in a new framework for thinking about disease.
The range of experiences In people infected with SARS-CoV-2, the virus that causes COVID-19 ranges from symptom-free to hospitalization and death, a recent observation by NIAID Director Anthony Fauci and other experts.
- “In SARS-Cov-2, there is an extreme divergence in host responses. We still don’t know what is leading to that,” says immunologist José Ordovas-Montañes of Boston Children’s Hospital.
Details: Many people have mild symptoms of the disease, or none at all, which means they can unknowingly transmit and spread the virus and complicate efforts to control its spread.
- 40% to 45% of people infected with SARS-CoV-2 do not develop symptoms, according to an estimate based on several case studies.
- In comparison, 13% of healthcare workers infected with SARS-CoV-1, the virus behind the 2003 epidemic, were asymptomatic in a study in Singapore.
- But for many respiratory viruses, the infection rate without symptoms is more than 70%.
At the other end of the spectrum. About 1 in 5 people are infected and need to be hospitalized.
- Beyond pneumonia and acute respiratory distress syndrome, the long and varied list of common manifestations of COVID-19 in hospitalized patients includes cardiac, neurological, renal, hepatic, gastrointestinal, endocrine, thrombotic, and dermatological complications, according to a recent review. by Aakriti Gupta from Columbia University Irving Medical Center.
- “This virus is proving to be more than just a respiratory virus in terms of manifestations, which we’ve seen with other respiratory viruses,” says Amesh Adalja, principal investigator for the John Hopkins Center for Health Safety.
- Other viruses, like the flu, SARS-CoV-1, and Ebola, can affect the body in multiple ways.
- But with COVID-19, “the proportion of people this multi-organ injury occurs in is higher than anything we’ve seen before,” says Gupta. For example, 40% to 50% of patients hospitalized with COVID-19 and up to 80% of patients admitted to the ICU have acute kidney injury, usually in addition to lung injury, compared to approximately 7 % of SARS patients.
The intrigue: Other pandemic viruses, such as the 1918 flu, may have had a wide range of different results, but molecular tools and diagnostics did not exist to detect them. Or in the case of coronaviruses that cause the common cold and don’t kill people, we don’t pay attention to those differences or bother to look for them.
- But COVID-19 kills, and as data and science accumulate rapidly about the virus, the differences are more explicit and more concerning.
- “Each virus has this particular balance of the types of cases it will have,” says Ordovas-Montañes. “This virus has particularly captured our attention because of how balanced it is on that spectrum.”
What’s going on: The researchers are trying to figure out the factors behind the COVID-19 range.
There is the virus itself. “Coronaviruses are unusual because they attack the respiratory and gastrointestinal systems,” says Rachel Roper, a virologist at the University of East Carolina.
- SARS-CoV-2 objectives The ACE2 receptor on host cells to infect them. That receptor is expressed in many of the body’s tissues, and some studies find virus particles in cells of the heart, kidneys, and intestine, suggesting that it can reach other organs and possibly directly damage them.
- Or it could be that the virus is affecting the body’s innate immune responses, which affect the pathways that regulate key processes in the body or cause inflammation, any of which can allow the virus to reach unexpected organ systems.
There is the person who infects, with their genetics, behaviors and environment. A number of pre-existing conditions, for example previous lung and heart disease, increases the risk of serious complications of COVID-19.
And there is the society in which that person lives. The geographic and racial disparities in this pandemic suggest that other factors, such as the distribution of health services, may need to be considered, says C. Brandon Ogbunu, an assistant professor at Yale University who studies the evolution of disease and ecology. .
- “Even more than other outbreaks, The variation from person to person, the multisystem nature, the way it affects demographics differently, the way the disease manifests itself differently in national contexts: it challenges a simple medical or biomedical narrative, “he says.
- COVID-19 may be more like non-infectious diseases, such as diabetes and schizophrenia, which have complex interactions with sociological, historical, and behavioral factors, “says Ogbunu.
The bottom line: “The history of understanding COVID-19 has been the history of understanding these diversities,” says Ogbunu. “This is a test of our modern understanding of what a disease is.”
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