Summer may have only recently given way to autumn, but it appears the flu season — often at its worst in the dead of winter — is starting to pick up, resulting in at least one death in New Mexico, state health officials announced this week.

In a Wednesday statement, the New Mexico Department of Public Health announced a woman from Bernalillo County died of the virus. She was 90.

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“Flu can be fatal if left untreated or if a person – at any age – has a weakened immune system,” said Kathy Kunkel, the New Mexico Department of Health’s cabinet secretary, in a statement. “Getting your flu vaccination every year is the single best way to protect you, your family, and our state’s most vulnerable residents, from infants to the elderly."

Additionally, health officials also confirmed cases of the flu in four other adults in the state. Three of the cases live in Sandoval County, while the fourth lives in Santa Fe County.

As flu activity typically begins to increase around October, per the Centers for Disease Control and Prevention (CDC), medical professionals recommend receiving the flu vaccine as soon as possible. It takes roughly two weeks for the vaccine to take effect, Michelle Lin, an emergency room doctor, and professor of emergency medicine at Mount Sinai in New York City, previously told Fox News.

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It’s especially important for pregnant women, young children and the elderly to get the flu shot, as these groups of people are typically the most susceptible to the virus.

It remains unclear at this time if the 90-year-old New Mexico woman who died from the flu had received the vaccine.

Separately, a 4-year-old California boy with underlying health issues died in September after testing positive for the flu.