About COVID-19 Epidemiology
Investigating COVID-19: The Science Behind CDC’s Response
When a new virus that causes disease in humans is discovered, scientists called epidemiologists work with other scientists to find who has it, why they have it, what health problems it causes, and what CDC can do about it. From the beginning of the COVID-19 outbreak, scientists at CDC and around the world have been working to identify the source of the outbreak, monitor and track the disease, study the disease, and develop guidance for actions.
Identify the source of the outbreak
Epidemiologists conducted surveys in the community and health facilities where the disease first appeared. They collected specimens using nose and throat swabs for laboratory analyses. These field studies took place in a community where many people live close together. The results showed who was infected, when they became sick, and whether they had traveled just before they got sick.
Monitor and track the disease
Using public heath surveillance systems, CDC keeps track of the number of COVID-19 cases over time and collects information on patient characteristics and risk factors. The types of data collected include case reports, hospital records, and death certificates, which have information like age, race/ethnicity, sex, symptoms, and health outcomes. With these data, CDC uses genomic surveillance to track the spread of variants, and monitor changes to the genetic code of SARS-CoV-2 variants and the impact on public health.
Study the disease
CDC scientists also use information from different kinds of studies to find out more about the disease and how it can be prevented. This includes how long someone with COVID-19 is contagious, risk factors for severe illness, the safety and effectiveness of vaccines, and longer-term health outcomes.
Develop guidance for actions to slow the spread of the disease and lessen its impact
Surveillance informs health guidance and improves public health response. CDC publishes resources to help people in different risk groups (like healthcare workers or older adults) stay safe in different community and institutional settings. This guidance is updated as new information become available.
- Read the latest reports of studies on COVID-19 from CDC’s Morbidity and Mortality Reports (MMWR).
- Learn more about epidemiology with CDC’s Introduction to Epidemiology.
- Review systems like the National Notifiable Diseases Surveillance System (NNDSS) that collects and sends data on cases of COVID-19 to CDC. This helps the agency monitor trends in cases within states and across the country.
- Search CDC Guidance documents for COVID-19.
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