The Valley Where Dusk is Death

A belt of poison night where death strikes with the dusk extends down the western slope of the Peruvian Andes. This death belt, first reported by a Spanish physician in 1630, consists of a few narrow valleys at an elevation of from 3,000 to 8,000 feet in an arid, very desolate and sparsely inhabited country. Nearly everyone who spends a night there is afflicted a few days later by a severe anemia which often proves fatal. This is the “verruga” disease. The red blood cell count drops very rapidly. It is not known whether the cells actually are destroyed by the disease, or whether it inhibits the forming of new ones from the bone marrow. The effect in either case is the same. The blood loses its capacity to carry oxygen and the victim slowly smothers.

The malady is known as Carrión’s disease. In 1885 a Peruvian medical student named Carrión inoculated himself with it to prove its identity. He succeeded in showing the cause, at the cost of his own life. He had been inspired to the foolhardy act by extreme patriotism. The Chile-Peru war was just over. Most work on the disease had been done by Chileans. Carión desired that the credit for medical research should come back to Peru.

If one recovers from the anemia a second stage of the malady sets in. The body is covered with wart-like growths, presumably due to some alteration in the blood supply to the skin. One attack gives immunity for life, but the death rate during the first stage is very high.

During daylight the death belt is perfectly safe. This has long been recognized by natives who travel through it freely between sunrise and sunset. The only permanent inhabitants of the region are persons who have recovered from the disease. The borders are sharply defined within a few yards of altitude.

For some years it has been recognized that the infection comes from the bite of a single species of sand fly—a vicious pest smaller than a mosquito. Protection is afforded only by special screens. Ordinary mosquito netting is worthless. The death belt is a place of bright sunshine nearly every day. The insects cannot endure light. They remain secluded and it is difficult to secure specimens, even when the hiding places are known. As soon as darkness comes they emerge in enormous numbers.

Harvard entomologists who investigated the death belt a few years ago spent the hours between sunset and sunrise in a specially screened railroad car. A few moments outside might have proved fatal.

Due to some delicate balance of nature this sand fly seems to be confined almost exclusively to this locality. It is credited with causing about 7,000 deaths in the decade before the last war.