Coronavirus (COVID-19) disease, caused by the severe acute respiratory syndrome coronavirus 2 virus (SARS-CoV-2), started circulating in December of 2019, and rapidly evolved into a global pandemic.The spread of contagious diseases like COVID-19 is often described using the SIR compartmental model. The three components are:
- S: The number of susceptible individuals. For the SARS-CoV-2 virus in December 2019, the entire population was susceptible since the virus was new to humans.
- I: The number of infectious individuals. These are individuals who are infected and are capable of infecting others that are susceptible to the disease.
- R: The number of resistant individuals. These are individuals who have been infected and have recovered and developed antibodies from the disease that prevent recurrence or those who have received an immunization and are substantially less likely to be susceptible to the disease.
Prior to the development of a vaccine, a contagious disease can be best managed by controlling the number of individuals that are infected, that is the number of active cases of the disease in the population. This report looks at two case rate measures, the number of cases in the total population per 100,000 population and the number of cases among Medicare enrollees per 100,000 enrollees—mostly adults ages 65 and older and younger adults with a disability. The higher the case rate, the greater the chance of additional individuals becoming infected and for the disease continuing to spread throughout communities.Infectious diseases like COVID-19 affect individuals differently. People who get COVID-19 can experience symptoms including a fever, fatigue and shortness of breath, among others. Some cases progress to severe illness which can be potentially life threatening. Others do not feel sick but can infect others. In addition to death, COVID-19 also poses enormous health, economic and social challenges to the population. Two included measures indicate the severity of the disease in the population; the COVID-19 death rate among the total population and the hospitalization rate due to COVID-19 among Medicare enrollees, a particularly vulnerable population. Increases in these rates add to the burden of the disease among the population.There are currently three vaccines that are authorized and recommended for use in the United States to prevent COVID-19 infection. Getting more people vaccinated will help slow the spread of SARS-CoV-2. The goal is to eventually achieve herd immunity, meaning that most of the population is immune to the virus and those who are not are protected by population immunity. This report includes two vaccine measures, the percentage of the total population who have been fully vaccinated and the percentage of older adults ages 65 and older who have been fully vaccinated.COVID-19 is a rapidly evolving health crisis. Continuously updated information can be obtained from the Centers for Disease Control and Prevention (CDC), the CDC COVID Tracker, National Institutes of Health, Centers for Medicare and Medicaid Services, state and local public health departments, and your healthcare provider.See also: