COVIDView: A Weekly Surveillance Summary of U.S. COVID-19 Activity

COVIDView Summary ending on April 18, 2020

Updated April 24, 2020

Download Weekly Summary pdf icon[42 Pages, 2 MB]

Key Updates for Week 16, ending April 18, 2020

Levels of influenza-like illness (ILI) declined again and are below the national baseline but remain elevated in the northeast and northwest of the country. Levels of laboratory confirmed COVID-19 activity remained similar to, or decreased slightly, compared to last week.  Mortality attributed to COVID-19 decreased compared to last week but remains significantly elevated and may increase as additional death certificates are counted.

Virus

The national percentage of respiratory specimens testing positive for SARS-CoV-2 at public health, clinical and commercial laboratories remained similar to, or decreased slightly from, week 15 to week 16 and is as follows:

  • Public health laboratories – increased from 17.8% during week 15 to 18.8% during week 16;
  • Clinical laboratories – decreased from 11.3% during week 15 to 9.6% during week 16;
  • Commercial laboratories – decreased from 22.8% during week 15 to 19.7% during week 16.
Outpatient and Emergency Department Visits

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 ILI and COVID-19-like illness (CLI) decreased compared to last week and levels of ILI are now below baseline.

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.

Severe Disease

Cumulative COVID-19-associated hospitalization rates since March 1, 2020, are updated weekly. The overall cumulative hospitalization rate is 29.2 per 100,000, with the highest rates in people 65 years and older (95.5 per 100,000) and 50-64 years (47.2 per 100,000).

Based on death certificate data, the percentage of deaths attributed to pneumonia, influenza or COVID-19 (PIC) decreased from 23.6% during week 15 to 18.6% during week 16 but remained significantly above baseline.  This percentage may change as additional death certificates are processed.

All data are preliminary and may change as more reports are received.

A description of the surveillance systems summarized in COVIDView, including methodology and detailed descriptions of each data component, is available on the surveillance methods page.

Key Points
  • Nationally, the percentage of laboratory specimens testing positive for SARS-CoV-2 remained similar to, or decreased, compared to last week.
  • Nationally, visits to outpatient providers and emergency departments (EDs) for illnesses with symptoms consistent with COVID-19 continued to decline and are below baseline in many areas of the country.
    • The decrease in the percentage of people presenting for care with these symptoms may be due to decline in 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.
    • At this time, there is little influenza activity.
  • The overall cumulative COVID-19 associated hospitalization rate is 29.2 per 100,000, with the highest rates in persons 65 years and older (95.5 per 100,000) and 50-64 years (47.2 per 100,000). Hospitalization rates for COVID-19 in older people are higher than what is typically seen early in a flu season.
  • Based on death certificate data, the percentage of deaths attributed to pneumonia, influenza or COVID-19 (PIC) decreased from 23.6% during week 15 to 18.6% during week 16 but remained significantly above baseline. This is very elevated in the context of any influenza season. The percentage may change as additional death certificates are processed.
  • Declines in some key indicators used to track COVID-19 from one week to the next could change as additional data are received but also may be a result of widespread social distancing measures.
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.

Summary of Laboratory Testing Results Reported to CDC*
Week 16
(April 12 – April 18, 2020)
Cumulative since March 1, 2020
No. of specimens tested 575,490 3,164,787
     Public Health Laboratories 72,345 401,159
          Clinical Laboratories 47,983 213,427
          Commercial Laboratories 455,162 2,550,201
No. of positive specimens % 107,703 (18.7%) 581,622 (18.4%)
     Public Health Laboratories 13,636 (18.8%) 62,686 (15.6%)
          Clinical Laboratories 4,585 (9.6%) 20,555 (9.6%)
          Commercial Laboratories 89,482 (19.7%) 498,381 (19.5%)

* Commercial and clinical laboratory data represents select laboratories and does not capture all tests performed in the United States.

Public Health Laboratories

Data Table

Clinical Laboratories

Data Table

Commercial Laboratories

* Commercial laboratories began testing for SARS-CoV-2 in early March, but the number and geographic distribution of reporting commercial laboratories became stable enough to calculate a weekly percentage of specimens testing positive as of March 29, 2020.

Data Table

Additional virologic surveillance information: Surveillance Methods

Outpatient/Emergency Department Illness

Two syndromic surveillance systems are being used to monitor trends in outpatient and emergency department visits that may be related to COVID-19. Each system monitors a slightly different syndrome, and together these systems provide a more comprehensive picture of mild to moderate COVID-19 illness than either would individually. Both systems are currently being affected by recent changes in healthcare seeking behavior, including increasing use of telemedicine and recommendations to limit emergency department (ED) visits to severe illness, as well as increased social distancing. These changes affect the numbers of people and their reasons for seeking care in the outpatient and ED settings.

ILINet

The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) provides data on visits for influenza-like illness (ILI) (fever [≥100F] and cough and/or sore throat) to approximately 2,600 primary care providers, emergency departments and urgent care centers in all 50 states, Puerto Rico, the District of Columbia and the U.S. Virgin Islands. Mild COVID-19 illness presents with symptoms similar to ILI, so ILINet is being used to track trends of mild to moderate COVID-19 illness and allows for comparison with prior influenza seasons.

Nationwide during week 16, 2.2% of patient visits reported through ILINet were due to ILI. This percentage is below the national baseline of 2.4% and represents the fourth week of a decline after three weeks of increase beginning in early March. The percentage of visits for ILI decreased in all age groups. Nationally, laboratory-confirmed influenza activity as reported by clinical laboratories has decreased to levels usually seen in summer months which, along with changes in healthcare seeking behavior and the impact of social distancing, is likely contributing to the decrease in ILI activity.

* Age-group specific percentages should not be compared to the national baseline.

On a regional levelexternal icon, the percentage of outpatient visits for ILI ranged from 1.1% to 5.4% during week 16; all regions reported a decreased percentage of outpatient visits for ILI compared to week 15 and six regions are below their region-specific baselines.

Overall Percentage of Visits for ILI | Age Group ILI Data

ILI Activity Levels

Data collected in ILINet are used to produce a measure of ILI activity for all 50 states, Puerto Rico, the District of Columbia and New York City. The mean reported percentage of visits due to ILI for the current week is compared to the mean reported during non-influenza weeks, and the activity levels correspond to the number of standard deviations below, at or above the mean.

The number of jurisdictions at each activity level during week 16 and the change compared to the previous week are summarized in the table below and shown in the following maps. The decreasing percentage of visits for ILI described above are reflected in this week’s ILI activity levels.

ILI Activity Levels
Activity Level Number of Jurisdictions
Week 16
(Week ending April 18, 2020)
Compared to Previous Week
Very High 1 -1
High 7 -3
Moderate 3 -3
Low 8 -1
Minimal 34 +8
Insufficient Data* 1 No change

*Data collected in ILINet may disproportionally represent certain populations within a state, and may not accurately depict the full picture of influenza activity for the whole state. Differences in the data presented here by CDC and independently by some state health departments likely represent differing levels of data completeness with data presented by the state likely being the more complete.

National Syndromic Surveillance Program (NSSP): Emergency Department (ED) Visits

NSSP is a collaboration among CDC, federal partners, local and state health departments and academic and private sector partners to collect, analyze and share electronic patient encounter data received from multiple healthcare settings. To track trends of potential COVID-19 visits, visits for COVID-19-like illness (CLI) (fever and cough or shortness of breath or difficulty breathing or presence of a coronavirus diagnosis code) and ILI to a subset of emergency departments in 47 states are being monitored.

Nationwide during week 16, 4.7% of emergency department visits captured in NSSP were due to CLI and 1.8% were due to ILI. This is the fourth week of decline in percentage of visits for ILI and the third week of stable or declining percentage of visits for CLI. All 10 HHS regionsexternal icon experienced a decline in percentage of visits for ILI and CLI.

Data Table

Additional information about medically attended outpatient and emergency department visits for ILI and CLI: Surveillance Methods

Hospitalizations

The COVID-19-Associated Hospitalization Surveillance Network (COVID-NET) conducts population-based surveillance for laboratory-confirmed COVID-19-associated hospitalizations in select counties participating in the Emerging Infections Program (EIP) and Influenza Hospitalization Surveillance Project (IHSP) states. COVID-NET-estimated hospitalization rates will be updated weekly.

A total of 9,483 laboratory-confirmed COVID-19-associated hospitalizations were reported by sites between March 1, 2020 and April 18, 2020. The overall cumulative hospitalization rate was 29.2 per 100,000 population. The highest rate of hospitalization is among adults aged ≥ 65 (95.5 per 100,000), followed by adults aged 50-64 years (47.2 per 100,000) and adults aged 18-49 years (14.3 per 100,000).

Among 2,803 cases with information on race/ethnicity, 43.7% were non-Hispanic white, 31.4% were non-Hispanic black, 12.4% were Hispanic, and 12.6% were other race, including unknown race.

Among 1,968 cases with information on race/ethnicity, 43.4% were non-Hispanic white, 32.0% were non-Hispanic black, 11.7% were Hispanic and 12.9% were other race, including unknown race.
Overall 0-4 years 5-17 years 18-49 years 50-64 years 65+ years
N (%) N (%) N (%) N (%) N (%) N (%)
Non-Hispanic White 1,224 (43.7) 3 (50.0) 2 (18.2) 173 (27.0) 334 (38.1) 712 (56.2)
Non-Hispanic Black 879 (31.4) 0 (0.0) 6 (54.5) 211 (32.9) 305 (34.8) 357 (28.2)
Hispanic 347 (12.4) 2 (33.3) 2 (18.2) 162 (25.3) 121 (13.8) 60 (4.7)
Other 353 (12.6) 1 (16.7) 1 (9.1) 95 (14.8) 117 (13.3) 139 (11.0)

Among 1,393 hospitalized adults with information on underlying medical conditions, 90.2% had at least one reported underlying medical condition, the most commonly reported were hypertension, obesity, chronic metabolic disease, and cardiovascular disease.

Additional hospitalization surveillance information: Surveillance Methods  | Additional rate data  |  Additional demographic and clinical data

Mortality Surveillance

The National Center for Health Statistics (NCHS) collects death certificate data from vital statistics offices for all deaths occurring in the United States. Based on death certificate data available on April 23, 2020, 18.6% of all deaths occurring during the week ending April 18, 2020 (week 16) were due to pneumonia, influenza or COVID-19 (PIC). This percentage is above the epidemic threshold of 6.9% for week 16 and represents the first week of a decline in PIC percentage since the end of February; however, data for week 16 are incomplete and the PIC percentage may increase as more death certificates are filed.

*Data during recent weeks are incomplete because of the lag in time between when the death occurred and when the death certificate is completed, submitted to NCHS and processed for reporting purposes.

Data Table

Additional NCHS mortality surveillance information: Surveillance Methods  | Provisional Death Counts for COVID-19