Michigan COVID-19 Timeline

Here we present a timeline of major COVID-19 milestones, executive orders and actions taken in Michigan to reduce crowding and enforce social distancing, and how the trajectory of cases has changed since COVID-19 began to appear in Michigan in March of 2020.

Early, aggressive action taken starting March 12th (by closing K-12 schools), through March 23rd, 2020 (issuing the Michigan Stay Home, Stay Safe order) appeared to curb the trajectory of COVID-19 infections in the state, ‘flattening the curve’. The stay at home order ended on June 1st, 2020, with case burdens significantly reduced.

Starting in October 2020, caseloads increased dramatically as the Republican legislature deemed Governor Whitmer's executive orders pertaining to COVID-19 to be unconstitutional. MDHHS subsequently issued some epidemic orders to enforce gathering limits and mask wearing, but November - December 2020 saw very high case counts, with some days exceeding 10,000 daily cases.

What is the relationship between changing behavior and COVID-19 case rates?

Since the discovery of the SARS-CoV-2 virus in China late in 2019, the disease caused by infection with this virus, COVID-19, has rapidly spread around the globe. In the United States, the first case was detected on January 22, 2020. Data from Johns Hopkins University shows that in the months since the first case was detected in the United States, there are now nearly ### reported cases and ### deaths across the country due to COVID-19.

There are currently three vaccines approved under Emergency Use Authorization (EUA) by the FDA in the United States: two two-dose mRNA vaccines made by Pfizer and Moderna, and a single-dose adenovirus-vectored vaccine made by Johnson & Johnson. Data from the CDC show that almost ### vaccines have currently been administered in the US, with almost ### Americans being fully vaccinated (including both doses of the mRNA vaccines). In Michigan, %%%% of the population aged 18+ is currently vaccinated against COVID-19, and %%%% of the population aged 65+ is currently vaccinated.

Even with a growing proportion of the population receiving vaccines against SARS-CoV-2, it is still important to maintain social distancing and mask wearing to further reduce the spread of COVID-19.

Understanding this Timeline

In evaluating the timeline above, it is important to acknowledge the delay between getting infected with COVID-19 and being sick enough to get tested for COVID-19. After exposure to COVID-19, it typically takes 4-6 days to develop symptoms, though it can take as long as 14 days.This means that there is up to a two week delay between when someone comes into contact with the virus (either through a sick person or touching a contaminated surface) and when they begin to show symptoms.

80% of those infected with COVID-19 appear to have mild to moderate illness, and may not seek testing at all. For those ~20% whose symptoms progress to more severe illness, it takes about 5-8 days to experience shortness of breath, 8-12 days to acute respiratory distress syndrome, and 10-12 days to be admitted to the ICU. Thus in settings where tests are administered most commonly to those who are experiencing severe symptoms and/or seeking hospital care, there could be as much as a month delay between exposure to COVID-19 and seeking treatment where a patient would receive a COVID-19 diagnosis. This means that we can expect up to a 4 week delay between changes in social distancing behavior and changes in case and mortality rates.

Over time, this delay is likely to have somewhat decreased, as testing capacity has increased in the state and tests are more readily available, yet there is still likely approximately a two week delay between becoming infected and testing positive for COVID-19.