LONG BEACH, Calif. (KTLA) — The health department in Long Beach, California, has confirmed its first human case of mosquito-borne St. Louis Encephalitis since 1984, city officials announced on Thursday.

The person who was infected was hospitalized but is currently recovering at home, officials said, and no other cases have been identified.

But what exactly is St. Louis Encephalitis?

SLE is a virus that can spread to people if infected by certain infected mosquitoes, though mosquitoes in the culex species are the most common carriers. The Centers for Disease Control and Prevention explains that the typical transmission cycle is that infected common birds (pigeons, sparrows, etc.) will be bitten by a mosquito. Infected mosquitoes then bite humans, passing on the virus.

People can’t transmit the disease to another person or pass it along to non-infected mosquitoes who bite them. Humans are considered “dead end hosts,” the CDC says.

Most people who have the virus don’t show symptoms, but those who do can experience fever, headache, nausea, vomiting, and tiredness, according to the CDC. In the most severe and rare cases, people may develop a neuroinvasive disease, a long-term disability, or can die from the disease.

While everyone is at risk for SLEV, people 50 years old and older with underlying health conditions are at greater risk of experiencing severe symptoms, a news release stated. There are no vaccines or medicines to prevent SLEV. However, healthcare providers can recommend treatments to aid with recovery.

The Long Beach Health Department said it hopes confirmation of SLEV in the city serves as a reminder to residents to protect themselves against mosquitoes, in addition to reporting possible mosquito control issues they might see.

Mosquitoes that transmit SLEV are most active at dusk and dawn, so residents out during those times are encouraged to adhere to the following guidelines:

• Use a mosquito repellent with DEET, IR3535, picaridin, or products containing oil of lemon eucalyptus. Lemon eucalyptus shouldn’t be used on children 3 years old or younger.
• Wear loosely fitted, long-sleeved shirts and long pants.
• Get rid of standing water around your property.
• Keep weeds, vines, hedges and grass trimmed; adult mosquitos like to rest in vegetation.
• Water in pet dishes, birdbaths and other small containers should be changed weekly.
• Swimming pools, spas and ponds should be properly maintained.

Twelve human cases of SLEV have been reported in California so far this year.

“We are working diligently with healthcare providers to educate the community to prevent more cases of SLEV,” Long Beach Mayor Rex Richardson said in a statement. “Mosquito control is a shared responsibility and residents must take an active role in reducing the threat of mosquito-borne illnesses in their neighborhoods.”