A Delaware family of four has been devastated by a severe neurologic illness reportedly related to insecticide sprayed into rooms they had rented in the Virgin Islands.

The story is nightmarish. Two parents rented a stunning beachfront property at Sirenusa on St. John, in the U.S. Virgin Islands (presumably) for their sons’ spring break. Soon after arriving, they fell ill—so quickly, it seems, that none of them had a chance to warn the others away.

The simultaneous pace of the illnesses—which reportedly involved seizures—suggests toxins, not infection, were the cause. All four were found in various degrees of distress, evacuated to the U.S. mainland, and now face an extremely uncertain and possibly tragic future.

Two teenage sons, Sean and Ryan Esmond, are said to be in a coma; the father, Stephen, is reportedly alert but paralyzed. The mother, Theresa Devine, seems to be doing the best of the group—in physical therapy but home.

Right now, all evidence points to a pesticide, methyl bromide, also referred to as bromomethane, as the cause of the neurologic problems. Methyl bromide is one harsh chemical. It’s effective at killing vermin but so toxic to people and the ozone that it was banned last decade by the U.S. and most other Western countries from routine use.

It is described as odorless and colorless so no one would know whether it was recently sprayed. One can imagine the scene of a cheerful clutch of tourists entering a glorious room excitedly and energetically then soon fading into a state of neurologic decomposure.

Methyl bromide’s neurotoxic effect is not fully understood. In exposed animals, cells in the central nervous system die after exposure. Likely there is a similar direct toxicity in humans as well. Indeed, methyl bromide and other so-called fumigants (used to super-sterilize soil pre-planting) are considered “highly acutely toxic,” alluding both to the rapidity and severity of the illnesses they cause. Symptoms range from headache to convulsions, dizziness, and tremors, as well as clumsiness and confusion. In addition, the lungs and kidneys may fail—a profile that, all in all, makes methyl bromide among the most toxic substances in use.

Methyl bromide not only is good at poisoning human neurologic systems; it also is extremely effective at killing bugs. Indeed, the same neurotoxin that is catastrophically affecting the Delaware family makes it a first-rate bug spray.

And methyl bromide is not the only toxic toxin that kills bug and man alike: The recent deaths of Canadian sisters in a Thai hotel are being blamed on phosphine, an unrelated chemical increasingly used in a post-methyl bromide world—though it too is poisonous.

The U.S. Department of Justice is investigating Terminix, that familiar anti-termite company in the bug-killing business. According to reports, they are the ones responsible for fumigating the room at Sirenusa where the Delaware family stayed. And presumably using chemicals outlawed in the U.S. but just-fine-thank-you in the Territories.

Terminix is playing it close to the vest, wishing the family a speedy recovery and promising to cooperate. Their track record, for a company that essentially traffics in chemicals does, not seem too awful. They’ve had the occasional slap on the wrist for shady business practices like skipping annual inspections, but no unusually horrific stories readily found by a serious Google search.

Much remains up in the air—the fate of the family involved; the confidence with which methyl bromide can be proclaimed the cause; the DOJ investigation. What is certain though is the problem the story has exposed. Poison is really handy stuff when you need to get rid of bed bugs and boll weevils and tomato fungus and all of the other natural but annoying (and even life-threatening) infections and infestations that bedevil the animal and plant kingdoms. Not to mention malaria and countless worms and parasites living in soil and water. For example, DDT was a great chemical—killed off mosquitoes and all sorts of trouble—but just happened to kill off everything else as well.

Our uneasy coexistence with nature creates these big messes every few years. Organic farmers who were pure and anti-chemical saw infections relating to their spinach and cantaloupe sicken thousands, killing some. Not to mention the German bean sprout E coli outbreak from a few summers ago.

The trade-off is the oldest one around: the disease (gnarled and discolored vegetables, bugs in your hotel room, higher wheat prices) or the treatment (such as toxins sometimes injurious to man). Stated another way—is the chemical-laced life worth living?

The answer in this case is pretty simple. The fact that these illnesses occurred outside the contiguous United States shows that the government, when left to use common sense, walks the tightrope between the opposing threats of too much unfiltered nature and too much brutal chemical pretty well. The Delaware family, sad to say, is a tragic example of just why regulation is so very necessary.