"Our best estimate right now is that for every case that was reported, there actually were 10 other infections," CDC Director Dr. Robert Redfield told reporters on Thursday as reported in the BBC News https://www.bbc.com/news/amp/world-us-canada-53186075.
This was because testing was restricted to people with symptoms and asymptomatic carriers were not tested, he said. "We probably recognized about 10% of the outbreak by the methods that we use to diagnosis between the March, April and May," he said.
Dr. Redfield said that between 5% and 8% of the population had been exposed to the virus and urged Americans to keep social distancing, wearing masks and washing hands.
Based on a detailed review of available evidence to date, CDC has updated and expanded the list of who is at increased risk for getting severely ill from COVID-19. Older adults and people with underlying medical conditions remain at increased risk for severe illness, but now CDC has further defined age- and condition-related risks. 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.
“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 MD. “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.”
Millions of Americans have probably had the coronavirus without knowing it, concludes officials at the CDC and many other experts. To date, 2.3 million Americans have had confirmed coronavirus infections, but by the CDC's estimates, the real number could be at least 20 million.
"Our best estimate right now is that for every case that was reported, there actually were 10 other infections," Dr. Robert Redfield, the director of the CDC, said during a call with reporters Thursday.
Redfield estimates that between 5% and 8% of the U.S. population has been exposed. He points to results from communitywide antibody tests and other surveillance measures that point to this range. But, he emphasizes, that leaves more than 90% of Americans who have yet to be exposed and who remain susceptible.
CDC also updated the list of underlying medical conditions that increase risk of severe illness after reviewing published reports, pre-print studies, and various other data sources. CDC experts then determined if there was clear, mixed, or limited evidence that the condition increased a person’s risk for severe illness, regardless of age.
There was consistent evidence (from multiple small studies or a strong association from a large study) that specific conditions increase a person’s risk of severe COVID-19 illness:
- Chronic kidney disease
- COPD (chronic obstructive pulmonary disease)
- Obesity (BMI of 30 or higher)
- Immunocompromised state (weakened immune system) from solid organ transplant
- Serious heart conditions, such as heart failure, coronary artery disease, or cardiomyopathies
- Sickle cell disease
- Type 2 diabetes
These changes increase the number of people who fall into higher risk groups. An estimated 60 percent of American adults have at least one chronic medical condition. Obesity is one of the most common underlying conditions that increases one’s risk for severe illness – with about 40 percent of U.S. adults having obesity. The more underlying medical conditions people have, the higher their risk.
CDC also clarified the list of other conditions that might increase a person’s risk of severe illness, including additions such as asthma, high blood pressure, neurologic conditions such as dementia, cerebrovascular disease such as stroke, and pregnancy. An MMWR published today further adds to the growing body of research on risk by comparing data on pregnant and nonpregnant women with laboratory-confirmed SARS-CoV-2 infection. Pregnant women were significantly more likely to be hospitalized, admitted to the intensive care unit, and receive mechanical ventilation than nonpregnant women; however, pregnant women were not at greater risk for death from COVID-19.
