Hantavirus 5-Point Screen Tool Identifies Patients With Deadly Infection

Hantavirus or coronavirus?

COVID-19 hit the Navajo Nation like a sledgehammer. Native Americans in rural areas, as many Navajo are, may have multigenerational and extended families living in tight quarters, with limited access to running water, miles from the nearest healthcare facility. They were particularly vulnerable to a virus that thrives on close contact, at a time when the most common preventives were distancing, frequent handwashing, and testing. By May 2020, the Navajo Nation had surpassed the epicenters—New York and New Jersey—in cases of infection. Even as late as November 2021, the Navah Nation has reported > 37,000 positive cases, and nearly 1,500 confirmed deaths, despite reaching a 70% vaccination rate.

Making things ever more challenging: How do you know whether the patient has hantavirus or COVID-19? The distinction is critical because the disease courses of the 2 infections differ greatly. “The importance of [TMC’s] work was really brought home by the COVID pandemic,” Mary Choi said. “The signs and symptoms of early COVID and hantavirus are really indistinguishable. But the problem is that most people with COVID will live, while most people with hantavirus will die without critical care.”

The overall US case fatality rates are drastically different: 36% to 38% for hantavirus, 1.6% for COVID-19. In Arizona alone, of 81 patients who developed hantavirus (as of 2019), 27 died. In New Mexico, of 117 patients, 51 died.

“The scary part,” said Tarrah Oliver, “was that when patients were flooding our ER with symptoms exactly like those of hantavirus, I kept thinking that it was now up to us in the lab to scrutinize CBC results for any characteristics of hantavirus because our locum providers and permanent providers would likely not have hanta on their minds right now to suspect it.”

“Once COVID hit Navajo Nation, we really worried about how clinicians were going to distinguish between the two disease entities and worried about possible excess deaths of hanta because they were mistaken for COVID-19,” Choi says. “Unfortunately, in the spring of 2020, 2 fatal cases of hantavirus were reported. Their deaths were initially thought to be due to COVID, but later testing showed that they both died of hantavirus. We knew that we had to study whether the 5-point screen could distinguish between hantavirus disease and COVID.”

They conducted the comparison study at TMC and Emory, in Atlanta. TMC, as a small hospital, might not get many COVID cases while Emory, a large hospital system, had many COVID cases but rarely hantavirus cases (Box).

The researchers found that the screen did indeed work as they had hoped. No matter who performed the screen, the demographics of the population screened, or when in the COVID-19 disease course the sample was taken, individuals positive for COVID-19 received a low score on the screen. None of the participants who were positive for COVID-19 demonstrated all 5 hallmarks of hantavirus infection, and only 3 patients received a score of 4.

The screen was most accurate when the specimen was collected during the cardiopulmonary phase. Before the cardiopulmonary phase [BOX], there is a short febrile prodromal phase in which the platelets are starting to drop but aren’t low enough to be considered thrombocytopenic. Hematocrit and hemoglobin levels are still normal, and immunoblasts or plasma cells haven’t been released into the blood yet. “A patient’s score is likely to be pretty low or intermediate,” Tarrah Oliver said. “In the febrile prodromal phase, the patient will have chills, fever, headache and myalgia lasting 3 to 6 days, which might be written off as the flu or even COVID-19, especially if a provider is not familiar with the endemic regions of the Navajo Nation.”

“When we found that the screen could distinguish between the 2 diseases,” Choi said, “we worked frantically to write up the findings and publish so that healthcare providers would be aware of the value of this tool.”