perhaps more sudden in this limited group than would be observed in the larger and more scattered population of a city. The decline of the epidemic is usually considerably slower than the rise, and in large cities the epidemic may continue for some time, even to several months. Incubation period. The incubation period in dengue is usually from 3 to 6 days, but has been observed to vary from less than 2 days to as much as 15 days. June. July. Aug. 15-21 22-28 29-5 6-12 13-19 20-26 27-23-9 10-16 17-23 24-30 After Kennedy -1912. Weeks: FIG. 1.-Incidence curve of dengue epidemic: Cases per thousand population, by weeks. Agramonte notes that two children returning to Habana from New York were stricken with dengue in 36 and 56 hours, respectively, after their arrival home. Vassal and Brochet note that the first case to appear on the steamship Kersaint, after arrival at the infected port of Saigon, occurred on the fourth day. Hare notes the occurrence of the disease in two men who visited an infected town for one day only, both of whom were attacked five days later. Adrien, after landing upon the infected island of Rouad, records the time of attack in, 20 men as follows: Three men on the fourth day. Seven men on the fifth day. Three men on the eighth day. Two men on the tenth day. In the experimental cases produced by infected mosquitoes the following incubation periods were noted: In the cases produced by the injection of blood, the following results were attained: Koizumi et al. report in their experimental cases an average incubation period of 5.4 days. It may be noted from the above figures that the incubation period observed by Cleland and his coworkers are longer than those observed by other experimenters. Variations in the dosage, state of the virus, or in the susceptibility of the subjects may be important factors in this determination. Cleland injected two groups of two volunteers each on two different occasions, with identical amounts of blood from the same patient, and found practically identical incubation periods in each pair of volunteers. These observations would point to the state of the virus as being of more importance than individual variation. Symptomatology. Judging from the literature of the subject, there is evidently considerable variation in the symptomatology and severity of dengue in different parts of the world and in different epidemics. Seidelin, commenting on the less frequent mention of the terrific pains in later epidemics, suggests that perhaps the older writers were wont to describe the very severe cases and to overlook milder ones. This variability in the symptomatology of the disease appears to be especially marked among outbreaks occurring on the Western Hemisphere. Onset. The onset is often without prodromal symptoms, or, when present, they are usually of a mild character, consisting of a chilly feeling, headache, pains in the back, lack of appetite, etc. The sudden onset may be typified by the attack in an unfortunate victim at Port Said, an account of which is quoted by Selim Saigh. The patient described it thus: "I have been out to work all day, feeling the same as usual; about sunset I had a headache, and, feeling tired, I sat on a chair to rest; suddenly I began to have pains all over, and half an hour later when I had to go home I was so stiff that two men had to support me all the way home." Primary erythema (primary rash).-During the first day or two of the disease the skin of the head, chest, neck, and arms is markedly congested. The features appear red, hot, and puffy, and the conjunctivæ and mucous membranes are injected. (The erythema may be best seen in some cases near the knees and elbows.) The patient may complain of a little soreness of the throat, but on examination there is only the congestion of the pharynx with, perhaps, a little dryness. During this stage of the disease the features have been described as resembling those following an alcoholic debauch. The erythema usually fades in a day or two, but may persist and merge. with the later secondary rash. Pains.-Agramonte describes headache, backache, and fever as an ever-present triad at the onset of dengue. The headache, usually severe, is perhaps oftenest located deep behind the eyes, but may be described as occurring in any portion of the head or often as "all over." Koizumi and others noted headache in 93 per cent of cases. Pains in the back, loins, muscles, and about the joints are very severe in many cases, and it is their severe character which caused Rush to apply to the disease the term "break-bone." Sandwith described them as "burning as if a hot iron were being pushed into the joints." These pains, when severe, together with the mental depression so often evident during convalescence, has induced some one to designate the disease as "the sum total of human misery." The pains, however, are fortunately not always so severe. Seidelin noted pains less commonly in India than usually described. Jones states that pains in the limbs were rare in the Philippines in 1907. Levy, at Galveston, 1919, states that many students suffering with dengue continued to attend medical classes regularly. Cleland and others mention "break-bone" pains as rare in their cases. Masterman states that the pains of dengue are less than in influenza, and Skae (also Meagher), in Bermuda, 1915, states that many cases were so mild as to be missed except for the presence of an epidemic. The writer suffered an attack without any notable pains of the limbs, and saw a number of such cases at Monroe, La., 1922; but there were also many patients who suffered with the more classical pains about the joints, and pains in the back were present in nearly all cases. A quite constant and rather typical symptom is pain in connection with the muscles of the eye, which results when the eyes are rotated. The eyeballs are also usually tender to pressure. Young children, it is often stated (Skattowe, Scott, et al.), suffer less than adults, and their convalescence is more rapid. Hare observed a few cases with initial pain in the testicles and groins. The writer saw one such case in Louisiana-a large, muscular negro who, when first seen, was almost maniacal with pain in both testicles. There was no swelling or other abnormality apparent. The pain yielded readily to codeia. Fever. As found in a few experimentally observed cases, mild fever may exist for some hours before the onset of other symptoms. With the onset of headache, etc., however, the temperature usually rises rapidly to its peak, 102° to 105° or higher. The fever is usually high for the first day or two and then begins to descend more or less rapidly, and may reach normal by the end of the third or fourth day and not rise again (see Fig. 2). There is usually an amelioration of the symptoms as the temperature falls. In the typical textbook attack, however, the temperature, either before or after reaching normal, on about the third or fourth day, begins to rise (see Fig. 3), giving the classical saddleback temperature curve of dengue. It is during this second rise of fever (seldom as high as the primary rise) that the secondary rash, when present, usually appears. After reaching its peak in the second rise, the fever usually descends either by crisis, in which case there may be profuse sweating, or more slowly, and it usually remains normal. It would seem that antipyretics may interfere with the normal temperature curve; however, Sutton states that they have little influence. Megaw and De Brun state that patients may suffer with typical pains and other symptoms of a mild character, but without rise of temperature; and the latter states that the eruption may occasionally be the only symptom of the disease. 97 Secondary rash.-The secondary rash is present, as noted by various writers, in widely different proportions of cases in different epidemics and localities. Rush states that it is almost universally found if looked for, as does Manson, Goldsmid, et al., while Charles 1 states that it is present in two-thirds of the cases, and Von Dühring, Rash 130 120 110 100 90 80 70 60 FIG 2.-Chart of temperature and pulse rate observed in dengue fever patient. (Solid line, temperature; dotted line, pulse rate.) in half the cases. Various physicians in the Philippines reported it to Wilson as present in from 10 to 100 per cent. No doubt some of the apparent discrepancies are to be explained by the difficulty of seeing a rash in dark-skinned peoples. 1 Quoted from Risk. |