The state had 212,942 COVID-19 cases—an increase of 1,281 from the previous day and 42 newly reported deaths, bringing the number of statewide virus-related deaths to 5,451 on Sept. 18 according to data from the Arizona Department of Health Services.


Of 3,906 diagnostic tests—which include polymerase chain reaction, known as PCR, tests and antigen tests— in Maricopa County reported on Sept. 18, 8.58%, or 335 tests, came back positive for coronavirus. The PCR test determines an active case of COVID-19, the other kind of testing data the state tracks is related to serology—or antibody—tests, which determines if a person has been infected in the past with the virus. Antigen tests "may not be as accurate or able to run as many patient samples per day, however, the quick results provide the ability to rapidly triage and make decisions," according to ADHS. The county also reported 34 new deaths Sept. 18, bringing the county's death toll to 3,199, according to data from the Maricopa County Department of Public Health.


Of the county's 3,241 known deaths, 1,106 are tied to long-term care facilities, making up 34.13% of the county's total COVID-19-related deaths.






The state and county also track hospitalization data. In Maricopa County, 10% of the county's total cases resulted in hospitalization as of Sept. 17. The county tracks intensive care unit, or ICU, data separately. One percent of the county's total cases have resulted in admittance to the ICU. Statewide, as of Sept. 18, ADHS reported 10% of the state's cases have resulted in hospitalization—21,865 cases across the state.


According to data from the state, of the completed and reported Maricopa County COVID-19 PCR tests, 13% of them have yielded a positive result.

Statewide, there have been 1,358,154 diagnostic tests completed. Of the total PCR tests across the state, 11.6% have yielded a positive result.