INTRODUCTION

Fevers of unknown origin still remain one of the most difficult diagnostic challenges in medicine. While technology such as F-fluorodeoxyglucose positron emission tomography (FDG-PET) [1] exists, clinicians often have to ordernon-clue based imaging and specific testing early in FUO work up. Fever of unknown origin may be caused by over 200 malignant/neoplastic, infectious [1]. rheumatic/ inflammatory, and miscellaneous disorders, therefore test ordered may be inefficient/misleading. Neurons in both the preoptic anterior and posterior hypothalamus receive two kinds of signals to control the human body temperature. One signal from the peripheral nerves transmit information from warmth or cold receptors in the skin and the other transmit signal from temperature of the blood bathing the region. These two are integrated by thermoregulatory center of the hypothalamus to maintain the normal temperature [2]. Normal human body temperature ranges between 36.5°C to 37.5°C. Other sites of the body have the following normal temperature, mouth 36.8°C, axilla 35.4°C, rectum 37.7°C and ear 36.8°C [3-5]. Fever, also known as pyrexia is defined as an elevation of the human body temperature that exceeds the normal daily variation (35.5°C-37.5°C) and occurs in conjunction with an increase in the hypothalamic set point, that is 37°C to 39°C. Fever is caused by infections either bacterial [6]. viral or fungal that affects the ears, lungs, throat, skin bladder or kidney. Other causes of fever include heat exhaustion, sunburn, conditions that causes inflammation such as rheumatoid arthritis, adverse drug reactions of medications, vaccination and immunizations, blood clots, autoimmune disorders, hormone disorders and illegal drug use. Classified in two ways, acute or chronic fever and continuous, intermittent, remittent or relapsing fever. Acute fever occurs in less than 7 days and is characteristics of infectious diseases such as malaria and viral-related upper respiratory tract infection. Chronic or persistent fevers is fever that occurs and lasts for more than or equal to two weeks’ duration and are typical of chronic bacterial infections such as tuberculosis, viral infections such as HIV, cancers and connective tissue diseases. However, any cause of acute fever can become persistent [6] or chronic if untreated. Continuous fever or sustained fever (Fig. 1-4) is defined as fever that does not fluctuate more than about 1°C during 24 hours, but at no time touches normal and are characteristic features of lobar and gram-negative pneumonia, typhoid, acute bacterial meningitis, urinary tract infections, among others [7,8]. Pyrexia of Unknown Origin (PUO)also known as fever of unknown origin ( FUO) was first defined by Petersdof in 1961 but over the year was refinedto any fever greater than or equals to 38.3°C several occasion with the duration of more than three weeks the least with no known diagnosis after many laboratory tests despite one week of inpatient investigations or three outpatient visits [9]. Infections account for approximately 25 to 30% of cases usually the most likely cause of FUO [10,1] followed by neoplasm and noninfectious inflammatory [11]. FUO can also be classified to intonosocomial, neutropenic, classic, and Human Immunodeficiency Virus (HIV)-associated FUO [12]. PUO mortality is low, antipyretics or antimicrobials therapy early on may delay diagnosis hence treatment before diagnosis not suggested [13]. In 2011, Fiji, had a concern over the rapid rise in reported cases of typhoid fever, leptospirosis along dengue fever locally known as the “three plagues” [6]. The three plagues are common etiologies of fever of unknown origin in Fiji. Other causes of FUO in Fiji includes dengue, rheumatic fever, measles, hepatitis, mumps, acute respiratory infections (ARI), TB, meningitis, viral illness Infections among others.

METHODOLOGY

Several research on FUO studies since the early 19thcentury to date has led to understanding and clinical implementation. This research is a retrospective study,with focus on available data on FUO and Fever caused by infection, using this criterion was more effective because most data on Fever and FUO in Fiji is due to infection, all age groups were included due to the elderly being susceptible to infection compared to young persons [14]. Data collected also included HIV and this was guided by a study that proved opportunistic infection and HIV can cause FUO, patient under HAART may have FUO at a smaller percentage compared to those not receiving HAART [15] and in Japan, HIV was the commonest cause of FUO due to increase in HIV patients [16]. Sources of information of this research were taken from online sources and reference textbooks and the main source of information data regarding diseases relating to FUO and fever were taken from the Ministry of Health, National Notifiable Disease Surveillance System Weekly Bulletin 2018 [17-22]. All data were tabulated and charts generated for data analysis was done using Microsoft Excel software. Herpes, hepatitis, denguewas tracked separately from other viral illness because they are of concern and endemic in Fiji. DISCUSSION In this study there are a significant number of cases of fever and fever of unknown origin in Fiji. The Western and Central division recorded the highest case of fever/FUO at 36,985 and 21349 in 2018 respectively this can be due to several factors as geographic condition and urbanization and accessible medical facilities. While the Northern and Eastern division recorded the lowest cases 3762 and 2489 respectively. Acute respiratory infection cases were the main reason of fever/FUO in Northern, Western and Central division (Fig. 5-8) followed by dengue except in the Eastern) where the main reason was viral illness, RI and dengue respectively. Dengue fever has been reported in Fiji over the years since the 19th century [2] as epidemic, to date there are still cases though controlled through vector borne clean up campaigns [3]. and public awareness on prevention. Acute Respiratory Infection can be caused by a number of pathogen ranging from bacterial, viral and fungal infection which are more influenced by the humid climatic condition, living conditions and other environmental factors such factories in those area. Others infections such as syphilis, dysentery – Bacillary, herpes, leptospirosis, amebiasis, meningitis hepatitis, measles, tuberculosis, rheumatic fever, mtyphoid fever, measles, hepatitis, mumps causes fever/FUO but this depend on the location climatic influence. Chlamydia, causes of FUO/Fever was insignificant in this study and some viral illness can cause acute respiratory infection. Other fever cases associated with fever of unknown origin such as TB, meningitis and typhoid fever were reported but were not as significant as that of acute respiratory infections and dengue fever. n ranging from bacterial (Tab.1-4)