How to Think About Covid Data Right Now

The number of Coronavirus cases has risen to new highs in the United States. Hospitalizations have reached levels not seen since the Delta wave. Deaths are only beginning to rise.

Although the overall pattern is not new, it is important to have a fresh look at how these metrics are interpreted. A faster, but less severe, variant is currently tearing through the country. Here’s how to think about the data in the coming days and weeks.

Omicron still has room for growth, as evidenced by case spikes

Coronavirus cases have surpassed all records in the United States in just days. The Omicron variant spreads quickly in almost every part of the country, even in areas with high vaccination rates. In the past week, all but 13 states have recorded record numbers.

Although these numbers are alarming, experts agree that they are not as alarming today as they were last year or even a few months ago. They should be used as a warning to the country to change policies and behaviors to reduce infections and protect those most vulnerable.

“The circumstances have changed and we must adapt,” said Dr. Shama Cash-Goldwasser, a senior technical adviser at Resolve to Save Lives, a global health organization. “We have a less severe variant, plus many are vaccinated, but evidence suggests the vaccines are not as good at preventing infection with Omicron as they were against Delta.”

Even though the number of Omicron cases in many areas is high, they are likely to be undercounted at this time. Many Omicron infections can be mild or asymptomatic, and many people don’t know how to test. Experts also say that testing shortages are limiting access to Omicron infections. A majority of results from popular athome tests are not reported by public health departments.

Experts warn that the sharp rise in cases in many states could be followed up by sharp falls, as was observed in South Africa. However, experts warn that even if there is a less severe variant, it could still result in significant numbers of people who are extremely sick.

“We are going to have a lot of people sick, and even if a smaller proportion of those individuals have really horrible illnesses and adverse outcomes, it’s still a lot of people,” said Janet Hamilton, the executive director of the Council of State and Territorial Epidemiologists.

Public health experts warn that there is a high risk of infection right now. They recommend keeping track of case trends and cases to encourage people to make informed decisions about how to protect themselves and avoid spreading infection to others.

“We’re still in a situation that needs caution,” said Ms. Hamilton. “We’ve had a month with Omicron and there’s just still a lot we don’t know.”

Hospitalizations show a system under strain

Omicron variants are less likely to cause severe illness. Hospitalization rates may not be as accurate as we thought. This could mean that we can learn less about the disease and more information about the impact on the health care system.

Hospitalizations have not yet seen the same explosive growth as cases, but this metric tends to lag case counts, and it may be too early to gauge Omicron’s full impact. It is clear that the number of people hospitalized for Covid in the United States has already exceeded the peak of the Delta-led wave, and it is still on the rise.

Hospitals, emergency rooms, urgent care centers and doctors’ offices are overburdened and understaffed across the country. Some hospitals are already closing down elective surgeries, and must also treat critical care patients at emergency rooms.

And in parts of the country like the Midwest, hospitals may be in a more precarious situation — they were already under strain, having yet to recover from the Delta surge before Omicron-led illnesses began to rise.

The hospitalization statistics are not perfect. “National data don’t allow us to distinguish between people hospitalized because of Covid-19 and those who happened to test positive while admitted for something else,” said Jason L. Salemi, an epidemiologist at the University of South Florida, who tracks Covid data.

These “incidental patients” may be more prevalent right now because Omicron is so transmissible. These patients could account for as much as half the hospitalizations in some hospitals.

Dr. Salemi pointed out that a coronavirus-related infection can still exacerbate the primary disease of incidental patients, pose a risk to staffers and cause an increase in the strain on medical centers.

The most recent national hospitalization data doesn’t include current measures of severe illnesses such as the number and length of stays or people on ventilators. Federal data tracks some of these, but it is approximately two months behind.

“The absence of these details about hospitalizations in the available data just muddy the water as we try to understand Omicron’s impact,” Dr. Salemi said.

Public health experts suggest monitoring Covid patients in intensive care as well as intensive care unit capacity to better gauge Covid’s impact on serious illness. One in four U.S. hospitals that have I.C.U.s reported recently that at least 95 per cent of their critical care beds were filled.

Death trends are still not clear

There is hope that improved vaccination coverage and medical treatment, as well as the milder Omicron variant, will make it less likely that infections cause death. High levels of mortality may still result from the high number of cases.

“Are we going to see deaths increase? Yes, we are,” said Ms. Hamilton of the Council of State and Territorial Epidemiologists. “And they are going to go up if cases keep increasing this way.”

The experience of the pandemic has shown that it takes at minimum three weeks for an increase to death rates to occur. This may explain why there has been a slight increase in death numbers.

Because of the time it takes to become seriously ill, and the time required to complete and file death records, trends in deaths often lag behind hospitalizations and cases by several weeks. This lag varies from one state to the next and can be longer when there are more deaths or when the public health system is overwhelmed by a surge in cases.

Already, there are alarming signs that death numbers are rising in some of the Northeast states hardest hit by Omicron, including New York and Connecticut.

According to Dr. David Dowdy of the Johns Hopkins Bloomberg School of Public Health, death can usually be predicted by looking at hospitalizations over the past three weeks and counting backwards by three weeks. This suggests that deaths will almost double within the next three weeks. However, it’s possible that deaths will not rise as rapidly as cases or hospitalizations have.

“This linkage between hospitalizations and deaths is being broken as well now, as more people are getting hospitalized for milder illness,” Dr. Dowdy said. “So I actually anticipate that deaths will not reach quite that level.”

“In any case, though, in the midst of major surges,” he said, “we can’t wait three weeks for data in order to act appropriately now.”

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