This CDC report provides a weekly summary and interpretation of key indicators that have been adapted to track the COVID-19 pandemic in the United States. While influenza-like illness (ILI) declined, it is still elevated and laboratory-confirmed COVID-19 activity continues to increase as do COVID-19 severity indicators (hospitalizations and deaths).
Public health, commercial and clinical laboratories are all testing for SARS-CoV-2, the virus that causes COVID-19, and reporting their results. The national percentage of respiratory specimens testing positive for SARS-CoV-2 increased from week 14 to week 15 and is as follows:
- Public health laboratories – increased from 17.3% during week 14 to 17.8% during week 15;
- Clinical laboratories – increased from 10.6% during week 14 to 11.5% during week 15;
- Commercial laboratories – increased from 20.6% during week 14 to 22.6% during week 15.
Two indicators from existing surveillance systems are being monitored to track outpatient or emergency department (ED) visits for potential COVID-19 illness.
- Nationally, the percentages of visits for influenza-like illness (ILI) and COVID-19-like illness (CLI) are elevated but decreased compared to last week.
Recent changes in health care seeking behavior are likely impacting data from both networks, making it difficult to draw further conclusions at this time. Tracking these systems moving forward will give additional insight into illness related to COVID-19.
Cumulative COVID-19-associated hospitalization rates since March 1, 2020, are updated weekly. The overall cumulative hospitalization rate is 20.0 per 100,000, with the highest rates in persons 65 years and older (63.8 per 100,000) and 50-64 years (32.8 per 100,000).
Based on death certificate data, the percentage of deaths attributed to COVID-19, pneumonia or influenza increased from 17.8% during week 14 to 18.8% during week 15.
- CDC has modified existing surveillance systems, many used to track influenza and other respiratory viruses annually, to track COVID-19.
- Nationally, the percentage of laboratory specimens testing positive for SARS-CoV-2 continued to increase.
- Visits to outpatient providers and emergency departments (EDs) for illnesses with symptoms consistent with COVID-19 are elevated compared to what is normally seen at this time of year but decreased compared to levels reported last week.
- At this time, there is little influenza virus circulation. The levels of people presenting for care with these symptoms are likely due to COVID-19 but may be tempered by a number of factors including less ILI overall because of widespread adoption of social distancing efforts and changes in healthcare-seeking behavior.
- The overall cumulative COVID-19 associated hospitalization rate is 20.0 per 100,000, with the highest rates in persons 65 years and older (63.8 per 100,000) and 50-64 years (32.8 per 100,000). Hospitalization rates for COVID-19 in older people are higher than what is typically seen early in the flu season.
- Based on death certificate data, the percentage of deaths attributed to COVID-19, pneumonia or influenza increased from 17.8% during week 14 to 18.8% during week 15.
U.S. Virologic Surveillance
The number of specimens tested for SARS-CoV-2 and reported to CDC by public health laboratories and a subset of clinical and commercial laboratories in the United States are summarized below. At this point in the outbreak, all laboratories are performing primary diagnostic functions; therefore, the percentage of specimens testing positive across laboratory types can be used to monitor trends in COVID-19 activity.
As the outbreak progresses, it is possible that different types of laboratories will take on different roles, and the data interpretation may need to be modified. The lower percentage of specimens testing positive in the clinical laboratories compared to the public health and commercial laboratories is likely due to the amount of COVID-19 activity in areas with reporting laboratories and a larger proportion of specimens from children.