Every hotspot has ‘its own curve’: How coronavirus cases are growing around the United States

March came in with a sickness and will go out with a surge.

An analysis of CNN’s daily state coronavirus case numbers not only reveals where the numbers are rising, but also suggests that the rate of new cases could be stabilizing in the state with the earliest outbreak.

President Donald Trump suggested during Monday night’s press briefing that he plans to lift his guidelines to “slow the spread” soon. Aides to the President are mining data on cases around the United States to see if there is any evidence that might show those current measures are working, even though the nature of the virus and the current situation make it hard to detect a pattern this soon.

According to CNN’s tally of US cases, there were at least 48,000 cases of the novel coronavirus in the United States as of Tuesday morning and more than 600 people have died. The total includes cases from all 50 states, the District of Columbia and other US territories, as well as all repatriated cases. CNN’s coronavirus tally is based on numbers of confirmed cases provided by state and local health departments.

CNN examined both raw case numbers and day-over-day rates of increase going back to March 1, when many areas began to see considerably larger numbers, perhaps in part due to wider testing.

When it comes to total numbers across the United States, the surge is clear and shows no signs of slowing nationally.

CNN’s tally of total confirmed cases has increased by at least 23% each day since March 4 — in some cases, much more steeply. From March 18 to March 19, confirmed US cases rose 51% in just one day, from 8,760 to 13,229, the largest one-day increase in recent weeks.

‘The data is so heterogenous’

Among the states, CNN’s analysis revealed that the sharpest day-to-day increases of confirmed cases were in New York, with an average increase of 63% each day over the last week.

New York, however, has also been aggressive in testing, and about 78,000 people have been tested in the state as of Monday, according to Gov. Andrew Cuomo.

Late Monday, Vice President Mike Pence said 313,000 tests having been completed nationwide — meaning that a sizable portion of those tested in the US have been in New York, which could explain the state’s heightened case numbers.

Experts caution that it’s difficult to draw solid conclusions from coronavirus case statistics, especially when comparing different states.

“The data is so heterogenous,” said Dr. William Schaffner, an infectious diseases specialist at Vanderbilt Medical Center.

Every state is approaching testing differently — by design or necessity — which makes it difficult to compare regions across the country.

In Washington, home to some of the earliest US Covid-19 cases, case numbers are still rising. But the rate of increase appears to have stabilized, increasing by an average of about 12% each day this past week, compared to an average of nearly 30% each day the week before.

Still, there isn’t enough data to declare a trend. Additional waves of outbreaks are common in viral epidemics. It’s also too early to attribute Washington state’s stable rate of newly confirmed cases to any one factor, as social distancing measures take time to make an impact.

Health experts in Washington state were cautious, too. At the University of Washington Department of Virology, which says it is conducting nearly all of the state’s coronavirus tests, researchers report that the rate of positive results from tests has remained stable since the beginning.

“That meaning, that pretty much the whole time we’ve been testing, only about seven to 8 percent of samples test positive, the rest negative,” said Dr. Keith Jerome, head of UW’s Virology Division. “As a local outbreak worsens, one expects the positivity rate to increase, meaning more people who have respiratory symptoms turn out to be sick from the novel coronavirus, rather than usual causes.

“So far we haven’t seen that increase in positivity. But could happen any time.”

And ultimately, the data do not show how many people have been infected. Instead, they reflect who has tested positive, which is dependent on having access to a test in the first place.

“The more telling statistic will be the number of people admitted into hospitals with known coronavirus infection,” said Schaffner, the Vanderbilt expert.

Up-to-date hospitalization data is hard to find on a national level. But Schaffner said that “if those numbers level off and start to decline, that’s when we can say we may start to find the downslope of the epidemic curve.”

So far, there is no evidence of those declines in the United States. And experts warn that hospitals around the country may not be ready to handle what could be a deluge of coronavirus patients in the coming weeks and months.

‘The seeds came in at different times’

CNN’s analysis also speaks to the extent to which different states see peaks at different times, raising questions about the White House Coronavirus Task Force’s nationwide 15-day period after which the administration would reconsider containment measures.

In CNN’s analysis, the 15-day period starting at the beginning of March saw large daily increases in states such as Washington, California and New York.

But Florida, Georgia, Louisiana and Tennessee only began to see sharply rising numbers in the second half of March. It remains unclear whether those dates reflect the beginnings of actual outbreaks, or stepped-up testing that revealed those outbreaks.

Dr. Deborah Birx, the White House coronavirus response coordinator, acknowledged these varying timelines in a press briefing Monday.

“Each state and each hotspot in the United States is going to be its own curve, because the seeds came in at different times,” said Birx.

“So, Washington state is on their curve they’re about two weeks ahead of New York,” she added.

Speaking on NBC’s “Today” show on Tuesday, Birx said the White House Coronavirus Task Force has been looking into being “laser focused” in battling the pandemic.

“The question is really can we be laser focused rather than generic across the country?” Birx said.

“In other words, can we use our data in a laser-focused granular way to really look at what’s happening on the ground and adjust our public health messages based on what is actually needed by the number of cases and the work that we’re doing with the communities.”