By the time the very first cases of COVID-19 were identified in the United States in January 2020, it was already clear that certain groups were at greater risk of serious illness, and possibly death, than others. In an effort to protect vulnerable populations, the Centers for Disease Control and Prevention (CDC) published a list of pre-existing health conditions that place certain groups at an increased risk of severe illness and death.

At first glance, the guidance seemed to focus on many of the same groups who are at risk of severe illness from the flu—including the elderly and people with chronic lung disease—but, by the time a national emergency was declared on March 13, 2020, it became clear that this was not the flu.

Babies, for example, were not included in the CDC’s list, even though they are considered to be at high risk of severe illness from the flu. Variations like this led to some confusion in the public about the nature of the virus and why it causes serious illness in some but not in others.

Because COVID-19 is such a new disease—and information about the virus is still evolving—the CDC has taken extraordinary steps to protect not only groups that have already been hard-hit by the pandemic but those that are presumed to be at risk based on past experience with other coronavirus outbreaks (like the SARS outbreak of 2003 and the MERS outbreaks of 2012, 2015, and 2018).

Adults 65 and Over

According to the CDC, the risk for severe illness with COVID-19 increases with age, with older adults at highest risk.

It is important to understand that having one or more risk factors for COVID-19 does not mean that you are destined to fall seriously ill if infected. On the other hand, having none doesn’t mean that you are inherently “safe.”

As of June 2, 2022, 74% of COVID-19 related deaths were in adults ages 65 or older.

There are several reasons for this, some of which are interrelated:

  • Loss of immune function: A person’s immune function invariably decreases with age, making them less able to fight common and uncommon infections.
  • Inflammation: Because the immune system of older adults is often impaired, it tends to over-respond with inflammation in an effort to curb the infection. In certain cases, the inflammatory response can spin out of control, leading to a cytokine storm.
  • Complications: Because older adults generally have multiple health concerns, a severe respiratory infection can end up complicating a pre-existing heart, kidney, or liver condition.
  • Decreased lung function: Because the lungs lose much of their elasticity with age, they are less able to sustain breathing without ventilation if a pneumonia-like infection develops.

Due to the underlying health risks, the CDC strongly advises that people 65 and over get vaccinated for COVID-19, limit in-person interactions (especially indoors), maintain social distance, and wash hands often.

Chronic Lung Disease

COVID-19 is a respiratory virus that attaches to cells via proteins known as ACE2 receptors. ACE2 receptors occur in high density in the esophagus (windpipe) and nasal passages, where the virus can cause upper respiratory symptoms.

But, in some people, the virus can move deeper into the lungs to the alveoli where ACE2 receptors also proliferate, causing severe and potentially life-threatening acute respiratory distress syndrome (ARDS).

People with chronic lung diseases are considered to be at a significantly increased risk for experiencing ARDS if infected with COVID-19. These include respiratory conditions like:

  • Asthma
  • Bronchiectasis
  • Chronic obstructive pulmonary disease (COPD)
  • Cystic fibrosis (CF)
  • Interstitial lung disease (ILD)

Despite these vulnerabilities, there remains debate on how “at-risk” people with some of these diseases truly are.

With that said, it is important to understand that risk from a statistical standpoint is not the same as the risk from an individual standpoint. People with advanced or poorly controlled lung disease, particularly those who smoke, are more likely than not to have compromised immune systems.

A 2021 review of 37 studies found an association between COPD and hospitalization, admission to intensive care units, and death from COVID-19. The same review did not find an association between asthma with negative COVID-19-related outcomes.

It is in this group of people that an uncomplicated upper respiratory infection can suddenly move into the lungs and turn severe.

Immunocompromised People

Immunocompromised people are those whose immune systems are weak, making them less able to fight infection. The loss of immune strength not only increases the risk of infection but also increases the likelihood of severe disease. Immune suppression characteristically affects:

  • People with HIV
  • People undergoing cancer chemotherapy
  • People with primary immunodeficiency
  • Organ transplant recipients

A study from the World Health Organization that included data from 24 countries, found that HIV was associated with an increased risk of severe COVID-19.  

A study in the United States conducted in New York also found that people with HIV and COVID-19 had higher rates of hospitalization and death and that risks may be highest for those with HIV whose CD4 counts are below 350 cells per microliter.

Researchers have also concluded that organ transplant recipients (most especially kidney recipients) and people undergoing chemotherapy are far more likely to get COVID-19 and develop ARDS than the general population.

Heart Disease

The respiratory and cardiovascular systems are inherently linked. Any oxygen delivered to the lungs is dispersed throughout the body by the heart. When a respiratory infection limits the amount of air that enters the lungs, the heart has to work harder to ensure that the diminished oxygen supply reaches vital tissues.

In people with pre-existing cardiovascular disease, the added stress on the heart not only increases the severity of high blood pressure but also the likelihood of a heart attack or stroke.

A March 2020 study published in JAMA Cardiology reported that nearly 28% of people hospitalized for COVID-19 experienced a coronary event, including a heart attack, while in hospital. Those who did were nearly twice as likely to die compared to those with no heart event (13.3% versus 7.6%, respectively).

Diabetes

Type 1 and type 2 diabetes can both cause abnormal increases in blood sugar (hyperglycemia) if not properly controlled. Studies suggest that the inability to control blood sugar is one of the main reasons why certain people are likely to get COVID-19 and experience worse disease.

Studies suggest that people with pre-existing heart conditions are three times more likely to die as a result of a COVID-19 infection than those with no pre-existing heart condition.

Acute hyperglycemia can lead to a condition called diabetic ketoacidosis, in which acids known as ketones impair the production of defensive white blood cells. This can increase a person’s vulnerability to infection. Even if ketoacidosis is not present, people with untreated or controlled diabetes tend to have some level of immune suppression.

According to a March 2020 study published in JAMA, involving 72,314 COVID-infected people in Wuhan, China, diabetes was associated with no less than a three-fold increase in the risk of death compared to people without diabetes.

While other studies have not reported such dramatic findings, blood glucose control does appear to influence the risk of COVID-19 infection in people with diabetes.

Liver Disease

Getting COVID-19 may complicate pre-existing liver disease in some people, as evidenced by research in which liver enzymes, called aminotransferases, are raised in those who are infected. Raised aminotransferases are an indication of liver inflammation and the worsening of liver disease.

A March 2020 study in the journal Metabolism concluded that people with type 2 diabetes who are able to maintain normal blood sugar levels are at a lower risk of infection and severe illness from COVID-19 than those who aren’t.

It is unknown how greatly COVID-19 affects people with liver disease, although most studies suggest that problem is limited to those with advanced or end-stage liver disease.

A March 2020 review of studies in the Lancet reported that people hospitalized for COVID-19 are twice as likely to have extreme elevations of aminotransferase. Even so, few of these individuals experienced any liver damage, and any increases in the enzymes were usually short-lived.

Chronic Kidney Disease

Chronic kidney disease (CKD) appears to increase the risk of severe illness and death in people with COVID-19. The risk seems directly tied to the severity of the CKD, with people on dialysis at greatest risk.

People with advanced CKD typically have suppressed immune systems, but other factors can contribute to increased risk. Because the function of the lungs, heart, and kidneys are interrelated, any impairment of one organ will impact the others. If a severe lung infection were to occur, for example, the symptoms of kidney disease would almost invariably be amplified.

According to a March 2020 study in Kidney International, the risk of death from COVID-19 is doubled if pre-existing kidney disease is involved. Most deaths occur when a systemic infection causes acute renal failure, typically in critically ill patients with advanced CKD.

Obesity

Obesity is a predisposing factor for many of the health conditions on the CDC’s list of pre-existing conditions for COVID-19, including heart disease, type 2 diabetes, fatty liver disease, and kidney disease

Despite the concerns, research published in the American Journal of Nephrology suggests that acute renal failure is still a relatively uncommon occurrence with COVID-19 and that COVID-19 will not aggravate CKD in most people.

Moreover, obesity is associated with impaired immunity, due in large part to the persistent inflammation that “blunts” the activation of the immune system.

While it is unclear how much obesity increases the risk or severity of COVID-19, epidemiologic research suggests that countries with high rates of obesity are generally at greater risk.

According to an April 2020 study in Obesity, the mortality rate of COVID-19 in countries like Italy, where obesity rates are high, is far greater than countries like China, where the obesity rate is significantly lower.

Neurological Disorders

Although not included in the CDC’s list of risk factors, some scientists have noted that certain neurological disorders, like multiple sclerosis (MS), Parkinson’s disease, or motor neuron diseases, may increase the severity of a COVID-19 infection by impairing swallowing (known as bulbar weakness), diminishing the cough reflex, or causing weakness of respiratory muscles.

At the same time, many of the drugs used to treat neurological disorders like MS and myasthenia gravis can actively suppress the immune system, increasing the risk and severity of COVID-19 infections.

Some health authorties warn that combination therapies used to treat these disorders, such as Azasan (azathioprine), CellCept (mycophenolate mofetil) or methotrexate combined with prednisolone, can cause severe immunosuppression. People on such regimens should take extra precautions to limit social interactions and maintain social distancing.

A Word From Verywell

Until scientists have a better understanding of COVID-19—including the ways in which it causes disease in different groups—anyone 65 and older or with a pre-existing health condition listed by the CDC should be considered to be at high risk.

Vaccination, social distancing, frequent hand-washing, and staying at home are the best ways to reduce your risk during the pandemic. Moreover, early treatment at the first signs of illness may prevent the progression of the disease and the development of ARDs.

Even if you are younger and have none of the risk factors outlined by the CDC, don’t assume that you are in the clear. If anything, taking the same preventive steps can reduce the spread of COVID-19 and end the pandemic faster.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.