War Surgery and Medicine
CHAPTER 5 — Dengue
EPIDEMICS of dengue fever have occurred frequently in the Pacific area over many years, and it is not surprising that our troops in New Caledonia and Fiji suffered from this disease. There was no dengue recorded in the Middle East Forces.
Dengue fever is endemic in the Pacific area and is present in the Philippines, Hawaii, New Guinea, New Britain, the Solomons, Fiji, and Samoa. It is highly contagious and the virus is transmitted by mosquitoes—the Aedes aegypti in Australia and New Caledonia, and the Aedes scutellaris in New Guinea. Its prevention depends on the eradication of the vector by the removal of breeding places and the destruction of adult mosquitoes by spraying, as well as by the protection of the individual by protective clothing and repellent lotions during the day and by mosquito nets at night. All febrile dengue patients should be kept under mosquito nets day and night.
The major epidemics experienced by the New Zealand Expeditionary Force in the South-West Pacific were in New Caledonia, where there were 483 cases from April to July 1943 and 200 cases from March to May 1944. In the Royal New Zealand Air Force in the Pacific there was a high incidence of dengue at Espiritu Santo shortly after the establishment of the RNZAF station there. There were over 440 cases in the area in the twelve months April 1943 to March 1944. As the mosquito population was reduced the incidence of dengue fell away. From January to March 1945 there was an epidemic of dengue at Funafuti—43 cases were reported in a Catalina flight of about 130 men. Otherwise that area was almost completely free from dengue, there being only about 50 cases in the first eight months of 1945.
The Pacific Force was fortunate in the low incidence of dengue fever, and the disease had little or no influence on military operations. Nevertheless, the disease is important because of the danger of infection in endemic areas, and this demands adequate preventive measures.
The considerable epidemic that occurred among New Zealand troops in New Caledonia in the middle of 1943 was carefully page 549 studied by Colonel Sayers, Major Riley, and Captain Gatman. Of the 483 cases reported from April to July 1943, 176 cases were admitted to 4 NZ General Hospital, and of these 100 consecutive cases were selected for special study; detailed haematological studies of 50 cases were carried out.
Source of Infection and Transmission
The source of infection was in the local population where the disease appears to be endemic, becoming epidemic from time to time.
The virus was transmitted by Aedes aegypti which bred in towns and villages in man-made breeding places, e.g., cisterns, barrels, neglected spouting, empty tins, and other artificial collections of water. The mosquitoes were active both by night and day. This mosquito was not seen in rural areas where the camps were situated, and every soldier or nursing sister infected had paid a visit to one of the local villages. In some cases the visits had been of very short duration. In view of this troops were forbidden to enter urban areas unless permission was specially given, and this undoubtedly did a great deal to limit the size of the epidemic. Very few of the army personnel stationed in urban areas escaped infection.
Dengue is a distressing, incapacitating illness which strikes with dramatic suddenness. The incubation period, where it could be determined, varied from five to twelve days, most cases occurring after seven or eight days.
There appeared to be no premonitory symptoms.
The disease can usually be divided into three phases:
An initial fever of two to four days' duration.
An interval of twelve to forty-eight hours with temporary relief of symptoms.
A secondary fever of one to four days associated with a rash and a return of the general symptoms of the disease.
Most cases started with a feeling of chilliness which seldom developed into a true rigor. Malaise was marked in all cases but varied in intensity. Headache was severe and almost invariably frontal or fronto-occipital.
Eye symptoms were very prominent and included retro-orbital pain persisting right through the illness and pain on lateral movement of the eyes. The conjunctivae was congested in almost all cases. There was congestion of both bulbar and palpebral conjunctivae which began about the second day and persisted well page 550 on into convalescence. There was occasionally oedema of the lids, but no true conjunctivitis was seen. Photophobia occurred in about one third of the cases. One patient developed central choroiditis with exudate.
Backache was a distressing and constant symptom, usually worst in the lumbar region and more severe during the initial period of fever than later on. The backache was associated with limb pains, especially in the region of the knees. They were not as severe as described in textbooks and would not justify the old name of ‘break-bone’ fever. In the early half of the disease about half the patients complained of abdominal pain which appeared to be muscular in origin and associated with the backache and limb pains.
Anorexia was profound in nearly all patients and was very persistent; nausea occurred in half the patients and vomiting in 20 per cent. Insomnia was a troublesome feature, especially during the first three days, and some sufferers were depressed. On the whole the depression seemed to be much less with dengue than with sandfly fever. In this group of healthy young people depression was present in only a few patients, mostly nurses.
The pyrexia was usually of the ‘saddle-back’ type with an initial fever, a short period of remission, and a secondary fever. In 96 per cent of cases the fever lasted from five to seven days. The pulse was slow throughout.
Most patients had an initial flushing of the face, ears, neck, and upper part of the trunk, but the main or secondary rash which appeared between the third and sixth days was maculo-papular, the majority being rubelliform in appearance. It was first seen on the chest and back and ulnar sides of the forearms, spreading later to the feet and legs. The ‘drawers’ area was relatively free of the eruption. The rash became petechial in 11 per cent of patients, usually over the dorsum of the feet and on the forearms. The rash usually lasted from two to five days.
General glandular enlargement was the rule and persisted long after discharge.
Careful examination of the blood throughout the disease was carried out by Captain Gatman, and a very brief summary of his principal findings were:
Total Leucocyte Count: In all cases there was a leucopenia, the lowest figures being on the fourth, fifth, and sixth days. The average count on the fifth day was 2850 per cmm. and counts as low as 900 per cmm. were observed.
Neutrophils were greatly reduced and the average segmented cell count on the fifth day was 500 per cmm. There was a steep return to normal between the seventh and twelfth days.page 551
Lymphocytes were also reduced, but not to the same extent as the neutrophils.
Plasma and Turck cells were frequently seen. Eosinophils were absent throughout the disease. Changes in the leucocytes did not bear any relation to the severity of the symptoms or to the type of temperature curve.
Convalescence was fairly rapid in most cases but some complained of malaise and tiredness for a considerable period.
Dengue fever, therefore, although it has no mortality and has few after-effects, can temporarily incapacitate a force with explosive suddenness. Its main danger is for troops in urban areas. It is unlikely to seriously concern a force engaged in jungle warfare or camped in rural areas.
2 NZEF (IP)