According to my understanding, what most people call stomach flu isn't the flu at all. The flu, which is contageous as an airborn virus that a cough can easily spread, is mainly a resperatory infection accompanied by body aches, often in the joints, and fevers. Some forms of flu will also be accompanied by some abdominal discomfort and a bit of flushing, often resulting from the fever, but the main symptoms are experienced in the sinuses, throat, and lungs.
What most folks refer to as stomach flu is more of a viral, parasitic, or bacterial infection of the gastro-intestinal tract and was more likely introduced in something everyone ate or drank. The symptoms may include fever, and chills, but always result in nausea, vomiting, diarrhea or some combination of the three. If it was shared person to person, it was likely from more intimate contact or sharing a glass, dish, or some eating or cooking utensil.
If this fits the description, I would use a grain alcohol, such as vodka, to clean my kitchen surfaces, especially cutting boards, etc. This is probably the most important step. I would do the same for all bathrooms. I would also launder all clothes and bed coverings. If you keep pillows on the sofa and family members spent some sick time on the couch, you might want to spray them with some watered down alcohol and toss them in the dryer.
Grain alcohol is more effective than lysol and less toxic as well. Be sure to wear rubber gloves when using it as it really dries the skin. I'm a big believer in the basic three for cleaning: alcohol, baking soda, or vinegar.
Although you can't get it at a local store, there is a really pleasant smelling, perfectly natural, organic, and highly effective disinfecting household cleaner made by Young Living Essential Oils. Their Thieves Household Cleaner is the best. It is called Thieves because it uses a blend of therapeutic grade essential oils which a band of thieves in the middle ages used to soak their gloves in so they could lute the homes of plague victims without getting sick. It worked then and it works now. They also have Thieves lozenges, hand soap, etc. I'm not into selling, but I became a member just because their products are so good and I want to use them. A few of my friends signed up under me and I get a commission check that covers most of what I spend with them. It really isn't a bad deal at all and my friends love their stuff as much as I do. You can find them on line. If you would like some help, I can connect you with someone who knows more about it.