It’s bad enough to live with the annoying buzz of one winged invader. But when those little insects invite their friends over, your home can turn into the site of a full-blown house fly infestation. It’s a nightmare scenario. Thankfully, though, there are warning signs that can let you know if there’s a problem, and measures to take to keep flies away from your home and in their natural habitats.

We know that houseflies have been bothering people since the dawn of time. They have showed up in stories dating as far back as the Bible and Greek mythology, and reared their ugly little heads in historic art, too. They’ve long interested scientists, thanks to their unusual sex determination mechanism. And while their name suggests that they’re supposed to dwell in houses just like humans, they have the potential to be dangerous when they mingle among people. Housefly regurgitation and excretion can transmit diseases including typhoid fever, cholera, leprosy and tuberculosis. For this reason, a house fly infestation should be avoided at all costs.

An annoying fly or two in your house probably isn't cause for alarm. But if you are frequently spotting large amounts of flies buzzing around your home, or have spotted several dead ones inside, you might have a fly problem. Learn how to spot the signs of an infestation by checking the areas that houseflies love: light and water. Look for clusters of houseflies in areas such as light fixtures, gutters, mulch piles and garbage bins. They also like food sources, especially ones that are decomposing. You might find clusters of feeding flies in areas where food is kept out in the open, such as fruit bowls or spills in a pantry. If you see several flies in areas like these, as well as dead flies scattered around your home, take measures to stop the intruders from invading any further.

To control a house fly infestation, try to find the source of the problem. Often, this is infested with fly larvae, also known as maggots. Larvae look like tiny pale worms, and they thrive in damp environments near a food source. You might find them in areas like compost piles or broken drain pipes. Once you find the larvae, you can pour boiling hot water and a half cup of bleach over them to kill them.

If you don’t find larvae, there are still several measures you can take to prevent an infestation. First, focus on sanitation. Be sure to clean areas that might have excess water or food residue, such as leaky pipes or spills under the fridge, and get rid of garbage before anything inside has a chance to decompose. In addition, take measures to seal places like screen doors, cracks and windows to ensure flies don’t have a way in from outside. Citronella candles have also been shown to keep flies away, as well as lavender-scented candles or plants. To control flies that have already made their way in, sticky traps found at your local hardware store can be an effective house fly killer. If the problem persists, you may need to contact an exterminator. They might use a fly repellant or other chemicals in order to get rid of the problem once and for all. Although houseflies come with the threat of disease, an infestation is manageable with the proper precautions and treatments.