Seven months into the Covid-19 pandemic, the United States is facing its third major rise in new cases. The country logged a record 148,302 cases Wednesday, and it has counted more than 100,000 new cases daily for the past week, according to an NBC News tally.
While the country has had three dramatic case increases, studying individual states reveals a pandemic that has played out differently from region to region and state to state. Different regions have contributed to each wave, and while states such as New York and New Jersey are trying to avoid their second or third surges of cases, states like North Dakota and Wisconsin are experiencing large increases for the first time.
The Northeast was the prime contributor to the country's first case surge in the spring, with New York, New Jersey, Pennsylvania and Massachusetts all having reached their highest daily case counts so far in the spring.
Cases in those states have declined substantially from their early highs, and governors and mayors are watching trend lines carefully and reopening their economies slowly. NBC New York reported that New York Mayor Bill de Blasio has floated closing indoor dining should the city's daily rate of new positive tests rise above a set threshold.
Health experts say case numbers spiked earlier in the year in states such as New York, which was the center of the pandemic in the spring, because of overcrowding and delayed public health response.
"There were probably very few, very unlucky chains of transmission, where people really infected others and it sort of took off," said Stephen Kissler, a postdoctoral fellow at Harvard T.H. Chan School of Public Health.
Kissler said the difference in peak times is due to varying social behaviors and public health responses in each state.
"Mask-wearing, rigorous distancing and restricting travel really do help keep cases down, and we have seen that in many different places," Kissler said.
Southwestern states, including New Mexico, Arizona and Texas, saw upticks in the mid- to late summer, which experts attribute to the warmer weather drawing people out of their homes where they had been socially distancing.
And while the country's current surge in Covid-19 cases is coming from almost all corners, states such as Wisconsin, Kentucky, South Dakota, Utah and Missouri are breaking records.
Experts attribute the late rises to several factors. In addition to the lack of statewide mask mandates in places like North and South Dakota, experts say it takes time for a virus to spread geographically from hard-hit regions.
Sturgis, South Dakota, was also the site of a 10-day motorcycle rally in August. An economic study in September found that the rally, which drew more than 400,000 people, could have led to more than 250,000 new coronavirus cases.
As fall and winter roll around, colder weather in those states could also be driving people indoors in close proximity to one another.
Dr. Bill Petri, chief of the Division of Infectious Diseases and International Health at the University of Virginia, said indoor spaces are "more dangerous" and increase risk of airborne infection.
Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security, said states that are experiencing peaks now, such as North Dakota, are more vulnerable than they were before.
"They weren't part of the first wave, which left a lot of susceptibility for a second wave," Adalja said.
"Not many states did something as explicit as New York did," he said, pointing to the New York state government's ability to provide contact tracing and administer tests with rapid turnaround. "I think that's one of the success stories of New York."
Experts now emphasize that states experiencing their first waves should take a holistic look at slowing the spread through adequate testing, contact tracing and communication.
"This formula is the same everywhere around the world: It's test, trace and isolate," Adalja said. "States that can do that fare much better."