The world continues its fight against a common enemy: the Covid-19 pandemic. The World Health Organization says that focus is still on saving lives and preventing new infections but among the many mysteries that remain about the disease is that why do some people are hit with Covid-19 harder than others? Why is it mild for some and deadly for others? Geneticists have previously found intriguing links between DNA and the risk of severe Covid-19. Heart disease, diabetes, increased age, and lifelong experiences of systematic racism (not race) are some risk factors. Now, researchers say that genes linked to immune reactions may also influence Covid-19 severity.
How genes may influence Covid-19 risk
In a study, which appeared in the New England Journal of Medicine, researchers conducted a genome-wide association study involving 1,980 patients with Covid-19 and severe respiratory failure at seven hospitals in the Spanish and Italian epicenters of SARS-COV-2 pandemic in Europe. After exclusion of population outliers and quality control, they detected cross-replicating links with rs11385942 at locus 3p21.31 and rs657152 at locus 9q34.2. These two “rs” refer to Single Nucleotide Polymorphisms also known as single DNA base pair variants and can be responsible for various biological differences between people.
Furthermore, the locus 3p21.31 and 9q34 refer to locations on chromosomes where those SNPs are found in the DNA. These are useful in the research as they can be linked with changes in a person’s immunity and a tendency to develop a certain type of disease.
The chemokines and innate immunity
David Ellinghaus, Ph.D and colleagues found that many patients with severe Covid-19 had variants in the complex of their genes on chromosome 3 and some of these genes encode chemokines, signaling proteins secreted by cells. Chemokines are also responsible for the release of innate immune cells from the bone marrow and serve as “chemical bread crumbs” to attract the immune cells to tissues that are under attack. Thus, they allow the tissues to destroy the infected cells. However, with coronavirus in the system, chemokines often trigger the assaults or go into overdrive that destroys the lungs, as published by Scientific American.
The scientists share that such a key variant was about 1.5 times more common in Covid-19 patients who were put on ventilator machines than those who only needed milder interventions. It was also found that severely affected patients with two copies of said gene variant were somewhat younger compared to those with only one or no copy at all.
Based on their findings, the authors suggest that such small change in the DNA has been associated with decreased activity of a gene that regulates chemokines. The DNA change is likewise linked with increased activity of another gene, which encodes a protein that interacts with the molecular gatekeeper called angiotensin-converting enzyme 2 or ACE2, allowing coronavirus to enter into the cells. ACE 2 is a human interferon-stimulated gene attached to the cell membranes in the intestines, kidney, heart, arteries, and lungs.
Covid-19 and Blood Type
Ellinghaus and the team also highlighted the association of Covid-19 risk on a chromosome that determines a person’s blood type. The DNA is found on chromosome 9. They said that patients with the gene for type A had 1.5 chances of experiencing respiratory failure than those with other blood types. On the other hand, those with type O had lower chances of respiratory failure.
The study findings are in agreement with a previous study conducted by Michael Zietz and Nicholas P. Tatonetti from Columbia University. Using observational data on 7,770 SARS-CoV-2-tested individuals at New York-Presbyterian (NYP) hospital, they found evidence that those with blood type A had a higher risk of getting Covid-19 and a lower risk for type O.
The Harvard Medical School, however, dispels these findings. It said that blood type is not linked with a severe worsening of symptoms in Covid-19 patients. HMS assistant professor of surgery Anahita Dua said that through their multi-institutional study, it should help put to rest previous reports of a possible link between blood type A and a higher risk for Covid-19 mortality and infection. For their study, they analyzed data of 1,289 symptomatic adult patients who tested positive for Covid-19. For now, Dua and the Harvard Medical team are “confident” that their principle finding will debunk the clinically unfounded misinformation and rumors.
Covid-19: Mild and Critical Condition
The July 29 statistics published by Worldometers show that out of the 5,798,093 infected patients on that day alone, only 1% of 66,509 are in serious or critical condition while 99% or 5,731,584 are in mild condition.
Our World in Data, a scientific online publication that focuses on large global problems, shared emerging Covid-19 success stories. These include Vietnam’s commitment to containment, Germany’s strong enabling environment, and South Korea’s policy changes after MERS.
It says that in 2015, South Korea struggled to appropriately respond to the outbreak of MERS despite having a robust health system. During the six months of that outbreak, South Koreans lived in fear and its government lost an estimated US$2.6 billion in tourism revenue while they spent $1 billion on treatment, diagnosis, and other response activities. After that outbreak, the country made a series of policy changes that helped improve their pandemic response and preparedness. This is why when Covid-19 struck the country, the learned lessons from the MERS outbreak inspired an aggressive and early government response. It also helped that people were willing to wear masks and cooperate with contract tracers.
In 2018, South Korea is among the countries with the highest number of hospital beds in public, private, general, and specialized hospitals and rehabilitation centers. It has 12.27 hospital beds per 1,000 people. Other countries on the list include Japan (13.05), Belarus (11), Russia (8.05), Turkmenistan (7.4), Ukraine (8.8), Germany (8), Hungary (7.02), and Austria (7.37).
The global spread of Covid-19 has strained the world’s healthcare systems and made it a critical challenge to identify most at-risk people. Examining the biology in Covid-19 cases may help find a route to therapies that could work across different cultures affected by the pandemic and not just some people with certain types of genes.