COVID-19 models forecast full Anchorage ICU capacity if current trends continue

Published: Oct. 6, 2020 at 8:35 PM AKDT
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ANCHORAGE, Alaska (KTUU) - Since early in the coronavirus pandemic, public health leaders have been using mathematical models to help understand the likely number of infections, hospitalizations and deaths, given certain factors. The most recent outlook shows intensive care unit beds in Anchorage being maxed out in about a month unless there is a change in the trajectory.

Dr. Tom Hennessy is an infectious disease epidemiologist at UAA and was the lead on the project that modeled the likely outcomes for COVID-19 in Anchorage, which the Municipality used to inform its decisions on COVID-19 emergency orders.

Hennessy says the “COVID Act Now” model, which was used in that report, proved to accurately predict the shape of Anchorage’s response to the virus. In essence, the model assumed that the shelter-in-place order would be carried out for three months; then after a month, it would be lifted followed by a spike in cases. In actuality, the shelter-in-place order lasted only about a month, but the spike in cases still came a month after restrictions were lifted.

Hennessy says that the models have focused on ensuring the number of cases requiring hospitalizations do not surpass hospital capacity. Since late May, the Centers for Disease Control and Prevention’s COVID-19 Surge tool has been the primary method for projecting that.

“We applied that model from March 25 to April 25 in retrospect and just saw how well it actually predicted what happened,” Hennessy said. “For example, that model predicted by April 24th there would be about 30 hospitalizations, and there were 34 actual hospitalizations. It predicted 360 cases in the month of April, we had 364 cases.”

Even the most accurate models are based on several assumptions, which Hennessy says makes projecting what is likely to happen in the future a challenge. However, several aspects of the current trend worry Hennessy and other public health leaders.

The total number of new cases reported in the last two weeks is the largest number of new active cases since the pandemic began. Additionally, the transmission rate has surged to higher levels. At the end of March, each positive case of COVID-19 was transmitted to 2.1 new people on average. Hennessy says that number was reduced to a transmission rate of 0.74 over the next month when restrictions went into place. However, the number of new cases each active infection has caused is increasing again.

On top of those two factors, Hennessy says the number of available hospital beds is smaller than earlier in the pandemic because some non-COVID-19-related procedures that were once canceled have resumed.

Earlier in the pandemic, a higher percentage of COVID-19 cases required hospitalization. Currently, only 4% of cases require hospitalization, but Hennessy says even with the percentage that low, it can overwhelm the health care capacity if the total number of cases gets large enough.

“The CDC Surge tool predicted a week ago when we ran it that we were about a month away from using up all the intensive care unit beds for COVID patients in the Anchorage area. And that was just based on Anchorage cases. That did not account for transferred patients from other parts of the state into Anchorage. So the actual picture might have been a little bit worse,” Hennessy said. “We have not been that close to using up the health care utilization, or ICU beds, at any point in the epidemic. So we’re closer to that wall now than we ever have been. And that’s worrisome. So this is all going the wrong direction I guess is the bottom line of this. Increased cases, increased transmission and less of cushion within our health care system that we could use to absorb increase in transmission and COVID cases.”

Hennessy says that there is no way to confidently predict when the current increase in cases will peak in Anchorage but says that improvements can come.

“There’s a lot of things that have happened in the last week,” Hennessy said. “If the president can’t be protected by testing, it’s a sign that we need to wear our masks and we need to take social distancing more seriously. So I think that may have given us all a teachable moment.”

Hennessy recommends that Alaskans get a flu shot this fall to stay as healthy as possible.

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