Acute Febrile Illness: Symptoms, Causes, and Treatment Options

One day you’re fine, and the next, your body feels hot, achy, and exhausted. Maybe there’s a headache, chills, or just a general sense that something’s off. This kind of rapid-onset sickness is often what doctors call an acute febrile illness.

Acute febrile illness (AFI) is a common medical condition that affects people of all ages. It is characterised by a sudden onset of fever, typically lasting less than two weeks. AFI can be caused by various factors, ranging from infections to non-infectious conditions. Recognising the symptoms and understanding the causes of AFI are crucial for early diagnosis and effective treatment.

Table of Contents

What is Acute Febrile Illness (AFI)?

Acute febrile illness, also known as acute undifferentiated fever or short febrile illness, is defined as a sudden rise in body temperature above 37.5°C (99.5°F). It is the body’s natural response to fighting off invading pathogens, such as bacteria, viruses, parasites, or fungi. AFI can vary in severity and may be accompanied by other symptoms like headaches, chills, muscle pain, and dizziness. While AFI often is cured on its own, it is essential to identify the underlying cause to provide appropriate care.

Common Causes of Acute Febrile Illness (AFI)

AFI refers to a rapid onset of fever, often accompanied by other symptoms such as chills, weakness, and muscle aches. The causes of AFI are diverse and can be broadly categorized into infectious and non-infectious factors. Here are the main causes of AFI:

Bacterial infections: Streptococcus (strep throat), E. coli (urinary and gastrointestinal infections), Staphylococcus (skin infections), and Typhoid (from contaminated food or water)
Viral infections: Coronavirus, Influenza, Dengue fever, Varicella (chicken pox), Measles, and HIV
Parasitic infections: Malaria (mosquito bite), Lyme disease (tick bite), and Giardiasis (contaminated water)
Fungal infections: Candida (yeast), Cryptococcus (meningitis), and Pneumocystis (pneumonia)
Non-infectious causes: Cancer, heat stroke, autoimmune diseases, and immunisations
Vector-borne diseases: Dengue fever, Zika virus, and various forms of encephalitis, particularly prevalent in tropical and subtropical regions
Other conditions: Inflammatory disorders, autoimmune diseases, and malignancies can also lead to AFI

Some non-infectious causes may mimic infections, especially in early stages, and require exclusion with appropriate testing.

Symptoms of Acute Febrile Illness (AFI)

Here are some of the most common symptoms of AFI:

Elevated body temperature above 37.5°C (99.5°F)
Headaches and dizziness
Sweats and chills
Muscle and joint pain
Weakness and fatigue
Respiratory symptoms such as coughing or wheezing
In infants or young children, fever may be accompanied by seizures
Nausea, vomiting, and lethargy in some cases

Diagnosing Acute Febrile Illness (AFI)

Diagnosing acute febrile illness involves identifying the underlying cause of the fever through a combination of clinical evaluation, laboratory tests, and specialised diagnostic tools. Various tests can help pinpoint the specific pathogen responsible for the illness.

1. Peripheral Smear Examination

A peripheral smear examination is a microscopic analysis of a blood smear to identify abnormalities in blood cells. This test is particularly useful in diagnosing infections such as malaria, where specific parasites can be observed within the red blood cells. The results of a peripheral smear examination can guide further diagnostic steps and treatment decisions.

2. Rapid Diagnostic Test (RDT)

Rapid Diagnostic Tests (RDTs) are quick and efficient tools for identifying common causes of acute febrile illness, such as dengue, malaria, and typhoid. However, it is important to use these tests sequentially rather than simultaneously to optimise accuracy and avoid lower diagnostic yields. RDTs provide a valuable first-line approach to diagnosing acute febrile illness.

3. ELISA (Enzyme-Linked Immunosorbent Assay)

ELISA is a serological test that detects antibodies or antigens in the blood. In the context of acute febrile illness, ELISA can confirm infections such as dengue fever by detecting IgG and IgM antibodies, and leptospirosis by identifying specific IgG and IgM responses. This test provides a reliable method for confirming the presence of certain infections.

4. PCR (Polymerase Chain Reaction)

PCR is a highly sensitive and specific molecular test that amplifies DNA or RNA sequences to detect specific pathogens. It is particularly useful for confirming diagnoses of acute febrile illnesses caused by viruses, bacteria, and other pathogens, such as dengue virus, leptospirosis, and Q fever.

Treatment and Management of Acute Febrile Illness (AFI)

The treatment and management of acute febrile illness aim to address the underlying cause of the fever while managing symptoms and preventing complications.

For high fevers or those causing discomfort, your doctor may recommend nonprescription medications such as paracetamol or ibuprofen to reduce fever and alleviate body aches and headaches.

General Measures:

Paracetamol (Acetaminophen) is first-line for fever control and pain relief.
Avoid aspirin or NSAIDs in suspected dengue due to bleeding risk.
Ensure adequate hydration with water, ORS, or clear fluids.
Get plenty of rest and maintain a cool environment.

Specific Treatment:

Antibiotics: Only if a bacterial infection is confirmed or strongly suspected.
Antivirals: Rarely used; may be prescribed for severe influenza or herpesvirus infections.
Antimalarials: Prescribed for confirmed malaria cases.
Hospitalisation: Required in severe cases with complications, hypotension, or suspected sepsis.

Note: Self-medication with antibiotics without diagnosis should be strictly avoided to prevent antimicrobial resistance.

Prevention of Acute Febrile Illness (AFI)

Preventing AFI involves several key strategies. Vaccination is available for some causes of AFI, such as typhoid fever, influenza, and COVID-19, and should be utilised to reduce the risk of infection.

Good personal hygiene practices are critical; wash your hands frequently with soap, especially before eating or using the restroom, to minimise the spread of infections.

Mosquito control measures, including using insect repellent, wearing covered clothing, and sleeping under mosquito nets, can prevent mosquito-borne diseases like dengue, malaria, and chikungunya.

Safe water and food practices are also important; drinking boiled water and ensuring food hygiene are important to prevent waterborne diseases like typhoid and amoebiasis. Avoid direct contact with infected animals to prevent infections such as leptospirosis and brucellosis.

Additionally, practise general precautions like handwashing, covering your mouth when coughing or sneezing, and not sharing utensils or cups to significantly reduce the risk of contracting AFI.

Complications of Untreated Acute Febrile Illness (AFI)

Untreated acute febrile illness can lead to severe and potentially life-threatening complications. Persistent high fever can cause organ failure, including kidney and liver dysfunction.

Severe infections like sepsis with shock, pneumonia, bronchiolitis, and aseptic meningitis can develop, particularly in infections such as murine typhus. Neurological complications, including cognitive issues, confusion, convulsions, and stiff neck, may occur due to the high body temperature and underlying infection.

Untreated AFI can also result in multiorgan involvement, affecting the central nervous system, lungs, kidneys, and muscles, leading to conditions like myositis and rhabdomyolysis. Early diagnosis and treatment are crucial to prevent these complications and reduce morbidity and mortality, emphasising the importance of understanding the causes and symptoms of AFI.

Conclusion

Acute Febrile Illness is a common condition with a wide range of causes. While many cases are self-limiting, early identification of the cause is critical to guide treatment, especially in regions prone to infectious outbreaks. Failure to treat AFI can result in severe complications, but with prompt diagnosis and supportive care, most individuals recover fully. Always seek medical attention for persistent or severe fever, and avoid self-medication.

Frequently Asked Questions (FAQs)

What are examples of febrile illnesses?

Examples of febrile illnesses include bacterial infections (e.g., streptococcus, E. coli, staphylococcus), viral infections (e.g., coronavirus, influenza, dengue fever), parasitic infections (e.g., malaria, Lyme disease), and fungal infections (e.g., candida, cryptococcus).

How long does an acute febrile illness last?

An acute febrile illness typically resolves on its own within two to three weeks.

What is the difference between “febrile” and “fever”?

“Febrile” and “fever” both refer to an elevated body temperature. However, “febrile” is a broader term describing the condition of having a fever, while “fever” is the specific symptom of elevated body temperature.

Who is a febrile patient?

A febrile patient is an individual with an elevated body temperature, typically defined as ≥38°C (100.4°F) or higher, indicating a potential infection or other underlying medical condition.

What is the febrile stage?

It refers to the active fever period, often with chills, sweating, and systemic symptoms.

Is an acute febrile illness contagious?

An acute febrile illness can be contagious depending on the underlying cause. For example, viral and bacterial infections are often contagious, while non-infectious causes are not.