The US Centers of Disease Control and Prevention (CDC) has expanded its list of those most at risk of becoming severely ill from coronavirus, warning that a substantial number of people are vulnerable.
The agency previously said that people aged over 65 years and older were at high risk of severe illness, reports the CNN.
On Thursday the CDC removed the age classification, saying that risk increased as people aged.
"[The] CDC now warns that among adults, risk increases steadily as you age, and it's not just those over the age of 65 who are at increased risk for severe illness," the agency said in a statement.
"Recent data ... has shown that the older people are, the higher their risk of severe illness from Covid-19."
The agency added that while age remained an independent risk factor for severe illness, the threat faced by older adults was also due to the group being more likely than younger people to have underlying heatlh conditions.
"Understanding who is most at risk for severe illness helps people make the best decisions for themselves, their families, and their communities," said CDC Director Robert Redfield.
"While we are all at risk for Covid-19, we need to be aware of who is susceptible to severe complications so that we take appropriate measures to protect their health and well-being."
The CDC also updated its list of underlying conditions which increase the risk of severe illness. The conditions are:
Chronic kidney disease
Chronic obstructive pulmonary disease
Obesity (BMI of 30 or higher)
Immunocompromised state from solid organ transplant
Serious heart conditions, such as heart failure, coronary artery disease, or cardiomyopathies
Sickle cell disease
Type 2 diabetes
The expanded list and the change to the age classification increases the number of people in high risk groups.
"As more information becomes available, it is clear that a substantial number of Americans are at increased risk of severe illness – highlighting the importance of continuing to follow preventive measures," the CDC said.