The Centers for Disease Control and Prevention (CDC) confirmed on Wednesday the United States’ first “severe” human case of H5N1 avian influenza—or bird flu, a zoonotic infection which has stoked fears of becoming the next global pandemic.

The severe case involves a resident of southwestern Louisiana who was reported as presumptively positive for infection last Friday. The infected patient “is experiencing severe respiratory illness related to H5N1 infection and is currently hospitalized in critical condition,” according to Emma Herrock, a spokesperson for the Louisiana Department of Health, who said that the patient is over the age of 65 and has underlying medical conditions but that further updates on their condition will not be given at this time due to patient confidentiality.

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It is the 61st case of human H5N1 bird flu infection in the country since April this year. But the CDC said the overall risk of the pathogen to the public remains low, and no related deaths have been reported in the U.S. so far.

Here’s what to know.

What caused the severe infection?

The CDC, in its Dec. 18 announcement, said that while an investigation is underway, the patient was found to have links to sick and dead birds in backyard flocks, making it the first known case of infection in the U.S. to have those origins.

Of the 60 other cases, 58 were linked to commercial agriculture—37 from dairy herds and 21 from poultry farms and culling. The sources of exposure for the two other U.S. human cases remain unknown.

What’s the current state of H5N1 human infections?

Of the human infections recorded in the U.S. this year, 34, or more than half, were in California, with all but one exposed to cattle. In response, Governor Gavin Newsom on Dec. 18 declared a state of emergency.

The CDC said that such a “severe” infection as was found in Louisiana was expected given cases in other countries. In Vietnam, a patient who died in March after a diagnosis of “severe pneumonia, severe sepsis, and acute respiratory distress syndrome” was found with an H5N1 infection, according to the World Health Organization. The U.S. appears to be leading in H5N1 infections across the world this year, according to CDC data on bird flu cases reported to the WHO.

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According to Mark Mulligan, Director of the Vaccine Center and the Division of Infectious Diseases and Immunology at New York University Grossman School of Medicine, the general population faces “no immediate threat.” Those who are in contact with birds and animals—especially those who work on dairy farms and cattle farms—are at greatest risk. Currently, no person to person spread of the virus has been detected.

“Right now we have to let the experts do surveillance, do sequencing of the virus to see if we're seeing any changes that portend any significant difference,” says Mulligan.

What are the symptoms?

According to the CDC, symptoms of the bird flu can vary. Many of the cases in the U.S. included symptoms resembling conjunctivitis-like eye issues, including eye redness, discomfort, and discharge.

Some cases also included both respiratory classic flu-like symptoms, including cough, headache, runny nose, fever, sore throat, body aches, fatigue, shortness of breath, and pneumonia, according to the CDC.

Read More: What Are the Symptoms of Bird Flu?

How can infection be prevented?

The CDC issued a number of protective measures, including largely avoiding direct contact with wild birds and other suspected infected animals as well as their bodily excretions. People who work with cattle and poultry on affected farms have a greater risk of infection, and are thus advised to monitor any possible symptoms of infection.

The CDC also recommends that those who work with poultry or other animals use the correct personal protective equipment (PPE)—including coveralls, boots, and more—which should be provided by employers.

Virologist and professor at John Hopkins University Andy Pekosz says that the severe case in Louisiana provides a reminder of an easy way to stay safe: stay away from dead animals. “You see a dead animal, if you're exposed to dead animals, stay away,” he says. “In many ways, it is the least likely way someone can get exposed, but in some ways, it's also one of the more preventable ways.”

Properly cooked poultry and poultry products are safe, and the CDC says that while unpasteurized (raw) milk from infected cows can pose risks to humans, it’s not yet known if avian influenza viruses can be transmitted through its consumption.

Both Mulligan and Pekosz say it is also important to get the seasonal human influenza vaccine. They say if there were to be a case of a person with simultaneous bird flu and human flu infection, it could lead to a “reassortment” and thus a virus that could be more easily spread.

“We know that has happened before, because the 1957 influenza pandemic and the 1968 influenza pandemic both were a result of a human and a bird influenza virus exchanging genetic material,” Pekosz says. “We know that the flu vaccines are not perfect, but they do a good job of reducing infection.”

The CDC currently has a program to offer seasonal vaccines to farm workers in high risk scenarios in certain states.