Las Vegas' most popular tourist resorts need to strip those sheets STAT ... 'cause a massive outbreak of bed bugs has been discovered over the last few months.

The creepy crawly pests have been found at Encore, the Venetian, the Mirage and the Excalibur Hotel and Casino ... after Southern Nevada Health District (SNHD) inspectors were called in to check things out -- this according to health records cited by 8 News Now. So, you may wanna reconsider plans if you've got a stay booked at any one of those hotels.

The last bed bug discovery was in December when one of Encore's specifically trained bed bug-sniffing dogs discovered a live bed bug in a room when a guest filed a complaint. Thankfully, the room was taken out of service pronto.

Before that, the teeny-weeny parasites were discovered in rooms at the other three resorts up and down the Strip in September and October.

According to the Nevada Resort Association, the outbreak affected only four rooms across the four hotels, and they described the incidents as "extremely rare and isolated occurrences." They add members are taking swift action in accordance with health and safety requirements.

It's unclear how the blood-sucking bed bugs made their way to the resorts and if there's a link between them all -- but they all lie within a 4-mile stretch of one another ... and one thing about bed bugs is they do love to hitchhike through luggage and clothing, so the spread could've been facilitated that way.

This ain't the first time Vegas has been under siege by bed bugs ... they were previously discovered at seven other popular hotels between 2022 and 2023. The spots they hit up at the time were Caesars Palace, Planet Hollywood, Circus Circus, Palazzo, Tropicana, MGM Grand, and Sahara.