By Claire Gillespie
November 03, 2020
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Anyone would be relieved to test negative for COVID-19. But in Sue Ryan's case, she turned out to have something far more serious. Shortly after hiking and camping along the Colorado Trail in her home state, Ryan started experiencing symptoms that made her think she might have the coronavirus.

Ryan told local TV station KDVR Fox 31 Denver that she had headaches, a high fever, and difficulty breathing—all telltale symptoms of COVID. However, when she took a coronavirus test, it came back negative. Then her symptoms got worse, so she went back to the hospital for another COVID-19 test, which also was negative. After additional testing, doctors diagnosed Ryan with hantavirus.

What is hantavirus, and how are the symptoms similar? Here's what experts say.

What is hantavirus?

Hantavirus is actually a family of viruses transmitted in the air through rodent droppings, says the Centers for Disease Control and Prevention (CDC). Infection with any hantavirus can cause varied disease syndromes in people worldwide, such as hantavirus pulmonary syndrome (HPS) caused by hantavirus types in the Americas, and hemorrhagic fever with renal syndrome (HFRS), the result of hantavirus types in Europe and Asia.

Two hantavirus outbreaks have occurred in the US in recent years—10 confirmed cases of hantavirus infection in people who visited Yosemite National Park in August 2012, and 17 cases across seven states in January 2017. A man in China reportedly died of hantavirus earlier this year.

Covid vs. hantavirus symptoms

COVID-19 symptoms and hantavirus symptoms can overlap, infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security in Maryland, tells Health. "Like the new coronavirus, hantavirus can cause respiratory symptoms," he says.

The main symptoms of HPS are fever and muscle aches, particularly in the large muscle groups, like the thighs, hips, back, and sometimes the shoulders. Other possible symptoms are headaches, dizziness, chills, and abdominal problems, such as nausea, vomiting, diarrhea, and abdominal pain, per the CDC.

Symptoms of HFRS typically present within 1 to 2 weeks after exposure, and they include intense headaches, back and abdominal pain, fever, chills, nausea, and blurred vision. Some patients may also experience facial flushing, inflammation or redness of the eyes, or a rash. Subsequent symptoms may include acute shock, low blood pressure, and acute kidney failure.

COVID-19 may present in different ways, and some people don't experience any symptoms at all. The official list of symptoms, per the CDC, are fever or chills, cough, shortness of breath or difficulty breathing, fatigue, muscle or body aches, headache, new loss of taste or smell, sore throat, congestion or runny nose, nausea or vomiting, and diarrhea.

Are there other similarities between hantavirus and coronavirus?

Aside from shared symptoms, hantavirus and coronavirus don't have much in common. The new coronavirus is transmitted mainly from human to human through through respiratory droplets produced by an infected person. But hantavirus is not communicable between humans—it's spread by rodents, Dr. Adalja says. In the US, rodents who carry hantaviruses include deer mice, cotton rats, rice rats, and the white-footed mouse. According to the CDC, these rodents shed the virus in their urine, droppings, and saliva, and it can then be spread to people who breathe in the contaminated air.

How common is hantavirus?

Hantavirus rarely infects humans, says Dr. Adalja. Between 1993 and 2017, a total of 728 confirmed cases of hantavirus disease were reported in the US. Colorado had 151 of those cases, and 41 of them were fatal, per UC Health. By comparison, more than 9.3 million COVID-19 cases have been reported in the US since January, according to the Johns Hopkins Coronavirus Resource Center.

"Hantavirus may be much rarer than COVID-19, but it's a far more serious infection because the risk of mortalilty is much greater," Dr. Adalja says. Johns Hopkins Coronavirus Resource Center estimates the COVID-19 mortality rate in the US to be 2.5%. The hantavirus mortality rate varies depending on which virus is causing the disease, but may be as high as 15% with some strains of HFRS.

What about treatment?

Many hospitalized COVID-19 patients are treated with the steroid dexamethasone and anti-viral remdesivir—but these aren't approved treatments. In fact, there's no approved treatment or vaccine for the new coronavirus.

Nor is there a specific treatment, cure, or vaccine for hantavirus infection. Patients who go into intensive care with severe respiratory distress are intubated and given oxygen therapy. Other forms of supportive care, such as IV fluids and fever-reducing agents, may help with symptoms, Dr. Adalja says.

Medical experts who treated Ryan don't know exactly how she contracted hantavirus. But as with any infectious illness, recognizing that something is wrong and seeing a doctor or hospital for tests can boost the odds of being diagnosed correctly, getting the right treatment, and emerging from the illness without complications.

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDCWHO, and their local public health department as resources.

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