Dear Reader,

It's not clear from your letter if your whole family is becoming ill at the exact same time, or if the illness is working its way through the family, and is being passed back and forth.

However, you are right to be concerned. Contacting your health care provider is an excellent idea.

If different family members are ill at different times, you may have gotten a stubborn virus that keeps being passed from person to person. Many families end up accidentally "sharing" various viruses, and a viral gastroenteritis that marches through a family is pretty common. Viral gastroenteritis is an infection of the intestines that can cause the symptoms you mention: nausea, vomiting, diarrhea, fever. If your family is sharing this virus, antibiotics won't help. You can try to harness the virus and prevent its being passed along to other family members by making sure that everyone is washing their hands with warm water and soap every time they use the bathroom, and before and after preparing food and eating.

If your family is becoming simultaneously ill, then simultaneously better, and then simultaneously ill again, then what you've described is not a normal cycle for the flu (influenza) or for other viruses that are usually passed around families, roommates, or people living in close quarters. In fact, "around" is an important word here. Most viruses initially infect one or two people in the household, and then make their way through the others. Sometime that virus circles back to the first person who gets sick yet again, but it is unusual for a virus to infect an entire family at the exact same time. While a lot of different things might be causing your family's troubles, if your whole family is ill simultaneously, then the pattern you're describing sounds like one of exposure. When an entire family falls ill at the exact same time, they've probably been exposed to something at the exact same time. But what?

One possibility is food-borne illness (more popularly called "food poisoning"), either from eating at a home or out at a restaurant. If you are all eating the exact same dish of food at the exact same meal, and that food has some kind of contaminant in it, you might all become sick together. The organisms that most often cause food poisoning include Salmonella, Campylobacter, Listeria, E. coli, and Norwalk-like virus. You may want to think about how you are preparing foods:

• Do you wash your hands well before cooking?
• Do you rinse produce before you eat or peel it?
• Do you cook meat, eggs, chicken, and fish thoroughly?
• Do you use separate cutting boards for raw meats and produce?
• Do you refrigerate leftovers promptly?

If you want more specific advice about safe food preparation procedures and appropriate cooking temperatures for various foods, check out the following web sites:

• Centers for Disease Control and Prevention: "Foodborne Infections"
• "The World Health Organization Golden Rules for Safe Food Preparation"
• U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition: "Information about Food Preparation and Foodborne Illness"
• Partnership for Food Safety Education web site

A worrisome possibility involves exposure to some kind of poison in your environment. If your family uses any kind of fuel-burning appliances, hopefully you've got carbon monoxide detectors installed in your home. Whether you have these detectors or not, you need to have your fuel-burning appliances inspected every year. Your description of on-again, off-again symptoms could indicate a faulty fuel-burning appliance, which is intermittently putting out higher levels of carbon monoxide in the air, and sickening your entire family. This is a potentially life-threatening situation, and if you have fuel-burning appliances in your home, even if you do have carbon monoxide detectors, you need to get those appliances checked out immediately. In fact, until they've been checked out and cleared, don't spend another night sleeping in your home.

Here are some web sites you might want to consult about clean air in the home:

• U.S. Environmental Protection Agency: "Protect Your Family and Yourself from Carbon Monoxide Poisoning"
• American Lung Association fact sheet, "Carbon Monoxide"
• Consumer Product Safety Commission: "Carbon Monoxide Questions and Answers"

Hope you and your family feel better soon,

Alice

Related Q&As

Forgot to refrigerate leftovers — Still okay to eat?

Nausea: Causes and treatments

What medicine is there to treat food poisoning?

Waiter, there's blood in my soup — does the chef have any diseases?

Do I have a cold or the flu?

What's that growing in the refrigerator?!? A guide for storing and eating leftovers

Handwashing do's and don'ts

Traveler's diarrhea: Preventing and treating runs on the road

I'm vomiting and can't keep anything down -- Help!