As cases of the novel coronavirus now known as COVID-19 continue to rise worldwide, researchers have learned that older adults may be particularly susceptible to the respiratory illness, which can cause pneumonia and symptoms such as fever, cough and shortness of breath.
"The data coming out of China continues to say that the people who are at higher risk for severe disease and death are those who are older and with underlying health conditions,” Nancy Messonnier, M.D., director of the National Center for Immunization and Respiratory Diseases at the Centers for Disease Control and Prevention (CDC), said at a press briefing in early February.
Preliminary estimates suggested that the virus, which then had sickened tens of thousands and resulted in hundreds of deaths, had a fatality rate of about 2 percent. Early findings from China, which pertained to the first 17 people to die in the outbreak, revealed that their median age was 75, and a study in the New England Journal of Medicine found that the median age of the first 425 people infected with the virus was 59.
Underlying conditions play a role
This is typical of coronaviruses, a family that includes the viruses behind the SARS and ongoing MERS outbreaks as well as other respiratory viruses such as the seasonal flu, says Vineet Menachery, an immunologist at the University of Texas Medical Branch who studies the effect of coronaviruses on aging immune systems.
"During the original SARS outbreak, the lethality rate for the overall number of cases was 10 percent, but that lethality rate jumped to over 50 percent in people over the age of 50,” he says.
“Age and your condition in life will really drive your susceptibility. You may be in your 40s, but if you have these chronic health conditions, you're going to be more susceptible, just like you see with flu.”
Menachery points to two main reasons for older adults’ increased susceptibility to coronaviruses. The first: They are more likely to suffer from underlying conditions that hinder the body's ability to cope with and recover from illness, such as chronic obstructive pulmonary disease.
The second has to do with how our immune response changes with age, the exact mechanisms of which Menachery and other researchers still are working to fully understand. His research into coronaviruses has shown that older mice, for instance, experience more inflammation early on in the course of illness, perhaps “setting the table” for lung damage that can't later be overcome.
The coronavirus that became a global pandemic before mid-March, like the ones responsible for SARS and MERS, affects the part of the lungs where gas exchange — the delivery of oxygen to the bloodstream and the removal of carbon dioxide — takes place.