Vineet Menachery has made it his life’s work to study how and why coronaviruses affect elderly patients more severely than the young and healthy, using aging mice as models.
Menachery, professor of microbiology and immunology at the University of Texas Medical Branch, expects the coronavirus that causes COVID-19 will turn out to be similar to SARS and MERS in its impact on aging populations, along with those who have preexisting, complicating conditions such as diabetes, high blood pressure and heart disease.
What changes as people age is their immune response, and that’s why these viruses can be more deadly to the elderly than to a younger, healthier population, Menachery said.
It’s uncertain why this new coronavirus affects those with diabetes and cardiovascular diseases more seriously, but there are theories based on what scientists already know about related viruses.
“Diabetes and obesity have been associated with increased inflammation, and inflammation is a major driver of diseases,” Menachery said. “We know that people with diabetes do have more inflammatory disease.”
With coronavirus, the body is not reacting differently but at a higher capacity because of that inflammation.
“It causes damage to the lungs in a kind of escalating situation and it takes a lot of effort by the body to repair the damage, so there is more damage happening with less of an ability to fight it,” Menachery said.
It’s less clear why this coronavirus is so much harder on people with cardiovascular conditions such as high blood pressure and heart disease.
“COVID-19, a respiratory disease, causes the body to lose oxygenation, there is more stress on the heart and with some it’s just an added stress on top of the damage that has already been caused that a patient can’t overcome,” Menachery said.
With high blood pressure and heart disease, the heart is already stressed, pumping faster and harder, and the added stress of a coronavirus can just be too much, he said.
“These same trends are true for influenza and other infectious diseases as well,” he said. “These preexisting conditions have an effect on every part of your body, and infectious diseases like coronaviruses can exacerbate the stress of that.”
Menachery doesn’t predict the COVID-19 global pandemic will necessarily change the behaviors that contribute to high incidences of these diseases in Americans, but those with complicating conditions and everyone around them should certainly practice social distancing as long as the viral spread continues, he said.
Another reason for that is what Menachery and health professionals refer to as the viral load a person carries. Someone exposed more often to the virus will carry a higher load and likely will have a more severe case than average, even if they don’t have complicating factors, he said.
When swabs from the mouth and nose are tested, they indicate the density of virus in that person’s body. The more exposure, the higher the density. Health care workers, in particular, are at higher risk of having more serious cases of COVID-19 because of repeated exposure and a higher viral dose.
“Health care workers intubating and extubating COVID-19 patients, for example, are more exposed to airborne virus and get a heavier dose,” Menachery said.
From his research with mice, Menachery has seen that among older and younger mice exposed to the same amount of virus, the older ones are more likely to succumb, a simple conclusion that can lead to profound consequences in the global pandemic.
“The big thing is this is a very serious disease and limiting exposure is the safest thing to do,” he said. “It’s becoming very clear that there are people with no symptoms playing a role in spreading the virus and maintaining a healthy social distance is about all you can do.
“If you do that, you limit the amount of virus everyone is likely to come into contact with.”