The first case of the novel coronavirus in the United States was confirmed on Jan. 21, 2020 — a healthy 35-year-old nonsmoker who had just returned to Washington state from Wuhan, China. Since then, the U.S. has become the epicenter of the pandemic, reporting more total cases than any other country. As of mid-day on April 10, more than 470,000 people in the U.S. had been diagnosed with COVID-19, comprising about 27% of the more than 1.6 million cases worldwide.
Because each state’s outbreak began at a different time, as well as due to such variables as the extent of testing, integrity of data reporting, population density, and strength of physical distancing efforts, the virus has not spread uniformly across the states. More recently, the growth in the numbers of confirmed cases has started to spike in some states while it has started to slow in others.
Washington became the first state to report a COVID-19 case on Jan. 21. West Virginia was the last state to report its first case, on March 17. All states are now reporting cases, and every state except for Wyoming is reporting deaths. Only about two-thirds of states are reporting testing practices.
Population density is a clear factor in how fast the disease spreads, and three of the densest states — New York, New Jersey, and Connecticut — are among the states that have reported the largest increases since their first cases were reported.
While not always the case, the states with the slowest rate of spread are in general the states that reported their first cases earlier. The swift implementation of stay-at-home orders also appears to have had an impact on the rate of spread.
24/7 Wall St. used the latest data compiled by the New York Times Daily to calculate the percentage increase in reported confirmed COVID-19 cases over the seven days through April 9 — the latest day for which data is available.