More Minor Horrors

by Sir A. E. Shipley

Like other branches of human activity disease has its romantic and its unromantic side. Nobody can regard mumps or measles as romantic. On the other hand, yellow fever calls up all the romance of slave-trading, pirates and the Spanish Main, buccaneers, maroonings and other grisly horrors, whose sole redeeming feature was a touch of romance. Lovers of pirate stories—and who are not?—will always remember their graphic description of Yellow Jack in the West Indies.

We have probably always had disease with us since the creation of the world—that act of ‘impardonnable imprudence,’ as Anatole France calls it; but the first description of yellow fever only dates back to 1647, when an outbreak occurred in the Barbados. Then, as now, it devastated the shipping of the port, and was soon introduced by ships into St. Christopher and, later, into Guadeloupe. The following year it was in Cuba, and in 1655 in Jamaica, and it gradually spread throughout the whole of the West Indies until a century or more later it reached the Island of St. Thomas.

One of the peculiarities of the disease is that it frequently disappears from a given locality for long periods of time. For instance, it was absent in Barbados after the first outbreak until 1690, and when it recurred it was at first not recognised as being the same disease which devastated the islands forty-three years before. In the eighteenth century there was another break of fifty-four years, and similar breaks can be recorded in most of the West Indian islands.

Besides the West Indies, it is at present endemic in Brazil and on the west coast of Africa, and is common in Mexico. Whether the disease arose primarily in Africa and is part of the toll the American continent has had to pay for the slave-trade, or whether it was brought to the west coast of Africa from the other side of the Atlantic, is not certain. It apparently appeared as a regular disease in Brazil in the year 1849, and from that time onwards, with the exception of one year, has been a permanent trouble at Rio. From time to time the disease has been carried to neighbouring parts of America, especially to the Gulf, Central America, and the northern coast of South America. It has been introduced more than once into Monte Video and Buenos Ayres, and has even penetrated up the Parana as far as Asunçion. Every few years it extends into the Southern States and has even reached Philadelphia and Boston. With the exception of an outbreak in Leghorn in 1804, European epidemics have been confined to Portugal, Spain, and the Balearic Islands.

It will have been noticed that most of these outbreaks occur on the coast and then pass up the rivers. It is thus most probable that the disease is one which is brought mainly by ships. It is obviously a disease which must be guarded against by our troops fighting near the coast in West Africa, as well as such troops as are left in the West Indies. But, above all, it must be guarded against in relation to our shipping fleet and our Navy, operating off the South American coasts. The danger, now the Panama Canal is open, of introducing the disease from America to Asia is a danger that should carefully be considered.

Yellow fever is a disease which requires a winter temperature of at least 68° F., for it is a mosquito-borne disease, and the yellow-fever mosquito flourishes best at about this temperature. It can be introduced into a new locality by the arrival of an infected mosquito, or by the arrival of an infected human being. In the former case the disease breaks out within a few days; in the latter at least ten or twelve days elapse before new cases arise, for, as we shall see later, the organism, whatever it is, that causes the fever is not capable of passing from the mosquito until it has been in its body for ten or twelve days.

Fig. 26.—Stegomyia fasciata. Female, lateral view (magnified.) Note hump-backed outline, and also the position of the posterior pair of legs.

Thirty-six years ago Finlay of Havana suggested that the virus of yellow fever was inoculated by mosquitos; but it was not until the publication of the discoveries by Sir Ronald Ross and others, that malaria is transferred by Anopheles, that a thorough investigation of yellow fever was made. In the last year of the last century an American Commission, consisting of Drs. Walter Reed, Carroll, Agramonte, and Lazear, investigated the whole subject, and, taking extraordinary risks, were able to prove that the infection was not conveyed by contact or through the air, or from bedding or clothes soiled by the dejecta of yellow-fever patients, but by a mosquito of the genus Stegomyia. Whatever the virus is, it is invisible, even under the highest powers of the microscope. It can be filtered through a Berkefeld filter. It is destroyed by heating to 55° C. If the blood of a yellow fever patient, during the first three days, be inoculated into a healthy man he gets yellow fever, and it is only during the first three days that the blood is infective. On the other hand, the mosquito is incapable of transferring the disease until the unknown organism has been in its own body for at least ten or twelve days.