Acute undifferentiated fever, defined as a sudden onset of fever without a clear underlying cause, is a common pediatric presentation that poses diagnostic challenges. ^[1] Acute undifferentiated fever is a common cause for which the patient seeks health care in India especially in June and September.^[2] Fever has become a common presenting complaint in developing world. ^[3] Precise information about major aetiologies of acute fever is important for affective management to reduce morbidity and mortality especially in developing countries including India. ^[4] The Acute undifferentiated fever is used to denote fever that do not extend beyond a fortnight and lack of localizable or organ specific clinical feature. ^[5]

In the western world, Acute undifferentiated fever is often due to self-limited viral condition. However, in the developing world the differential diagnosis of Acute undifferentiated fever includes potentially significant illness such as malaria, dengue fever enteric fever, leptospirosis, rickettsiosis, hantavirus and Japanese encephalitis. ^[6] Acute undifferentiated fever accounts for the majority of out patients visits and inpatient admission in India. ^[7] The causes for the same are variable and need a systemic approach to identify the cause of appropriate therapy. ^[8] In resource limited setting, fever may be treated empirically or self-treated due to lack of access to diagnostic tests. ^[9]

The study was aimed to find out the aetiologies and the clinical pattern of Acute undifferentiated fever. This study aims to provide a comprehensive understanding of the potential etiologies and clinical characteristics associated with this condition in the targeted age group.

This was a prospective, observational study conducted at a tertiary care pediatric hospital over a 12-month period. Children between the ages of 6 months and 15 years presenting with acute undifferentiated fever, defined as a temperature of 38°C or higher lasting less than 14 days without a clear source of infection, were enrolled in the study. A detailed clinical history, physical examination, and laboratory investigations, including complete blood count, inflammatory markers, and relevant microbiological tests, were performed to identify the underlying cause of the fever.

Data collected included demographic information, clinical presentation, duration of fever, laboratory findings, and final diagnosis. Statistical analysis was employed to determine the frequency, distribution, and associations between various etiologies and clinical characteristics

In present investigation, a sum of 300 patients with intense undifferentiated fever were assessed out of these 195 (65%) were male and 105 (35) were female (Table 1).

Table 1: Distribution of Gender

Table 2: Distribution of different age groups of patients

In Table 2, in our study, the most of the patients the age group of 3-5 years i.e., 95 out of 300 (31.66%), followed by 6-10 years, i.e., 75 out of 300 (25).

Table 3: Clinical Symptoms and sign.

In Table 3 out of 300 patients, most common symptom was pyrexia (100%), headache (54.8%), rhinitits (46.8%),

vomiting (48.33%), Rash (40%), Abdominal Pain (32%),

Diarrhoea (26.67%), cough (20%), hepatomegaly (11.67%)

and splenomegaly (5%).

Table 4: Acute febrile illness aetiology

In Table 4, in this investigation typhoid fever was the most well-known reason for undifferentiated fever (33.33%) trailed by malaria (25%), dengue fever (19.33%), urinary tract disease (8.33%), Acute gastroenteritis (5.66%), Pneumonia (3.33%), Bronchiolitis (2.66%), Hepatitis (1.32%) and Pharyngotonsillitis (1%%).

The findings of this study highlight the diverse etiological spectrum of acute undifferentiated fever in children, with viral infections being the most common cause. ^[7] This aligns with previous research, which has also identified viral illnesses as a leading contributor to AUF in the pediatric population. ^[8]

The study also underscores the importance of a comprehensive diagnostic approach, as the initial presentation of AUF can be non-specific and challenging to differentiate. ^[9] The combination of clinical history, physical examination, and targeted laboratory investigations played a crucial role in establishing the underlying etiology and guiding appropriate management strategies. ^[10]

The higher rates of hospitalization and intensive care support observed in the bacterial and tropical febrile illness groups emphasize the need for early recognition and prompt intervention to mitigate the risk of severe complications. ^[11] Healthcare providers should maintain a high index of suspicion for these potentially life-threatening conditions, particularly in regions with endemic tropical diseases. ^[12-15]

Our study has a few limitations. We have focused on Children (i.e., the most severely ill patients), our study findings should not be generalized to the acute febrile illness subtypes seen in outpatients or in the community. Patients were followed only until a diagnosis was confirmed or if patient recovered within the study period in case of miscellaneous fevers. Any patient who crossed over to FUO were not followed up. Treatment and recovery of the cases were not followed up after the diagnosis was made. Our results cannot be applied to adults. Several other infections that have been described to cause fever in the area were not systematically pursued. Important among this group are Japanese encephalitis, Hepatitis E, Epstein-Barr-virus, Hepatitis A, Hepatitis E, and Coxsackie virus, Influenza and other bacterial infections such as Q-fever, Brucellosisand Melioidosis.

This study provides valuable insights into the clinico-etiological profile of acute undifferentiated fever in children, highlighting the diverse range of underlying causes and the importance of a structured diagnostic approach. The findings underscore the need for healthcare professionals to maintain a comprehensive understanding of the epidemiology, clinical features, and management strategies for AUF in the pediatric population.

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