Differential Diagnosis of Dengue Infection

Dengue infection can manifest in various ways, from mild fever to severe bleeding or shock, which can make diagnosis tricky. Many other illnesses can look like dengue, especially in the early stages. Proper diagnosis is essential for choosing the right treatment and avoiding unnecessary complications. Below are some conditions that commonly resemble dengue and should be considered during evaluation:

1. Malaria

Both malaria and dengue are mosquito-borne diseases, and they share similar symptoms such as high fever, chills, headache, and muscle aches. However, malaria typically presents with a cyclical fever pattern and may cause an enlarged spleen. Blood tests, such as blood smears or rapid diagnostic tests, are essential to differentiate malaria from dengue.

2. Chikungunya

Chikungunya, another mosquito-transmitted viral illness, can be mistaken for dengue due to its high fever and muscle pain. However, chikungunya tends to cause more intense and long-lasting joint pain, which can persist for weeks or months. A specific blood test, such as serology or PCR, can confirm whether the infection is chikungunya or dengue.

3. Zika Virus

Zika virus shares several symptoms with dengue, including fever, rash, and joint pain, but Zika is generally milder. Conjunctivitis (red eyes) is more common in Zika, and unlike dengue, Zika can lead to complications during pregnancy. Laboratory tests can help distinguish Zika from dengue.

4. Leptospirosis

Leptospirosis is a bacterial infection that can mimic dengue, with symptoms like fever, headache, and muscle pain. However, leptospirosis often leads to kidney or liver problems, sometimes causing jaundice and red eyes. Blood and urine tests can help identify leptospirosis and rule out dengue.

5. Typhoid Fever

Typhoid fever, caused by Salmonella typhi, presents with fever, fatigue, and abdominal pain, much like dengue. Unlike dengue, typhoid is usually associated with digestive symptoms like constipation or diarrhea, and the fever tends to increase gradually over time. Blood cultures and Widal tests can confirm typhoid.

6. Influenza (Flu)

Flu symptoms such as high fever, headache, and muscle pain can resemble dengue in the early stages. However, influenza usually includes respiratory symptoms like a cough, sore throat, and a runny nose, which are not typical of dengue. Rapid influenza diagnostic tests (RIDTs) or PCR can confirm the flu.

7. Rickettsial Infections (Scrub Typhus)

Rickettsial diseases, such as scrub typhus, can cause fever, headache, and muscle pain similar to dengue. However, scrub typhus may include a distinctive dark scab (eschar) at the site of the mite bite and swollen lymph nodes. Serology and clinical signs help in diagnosing this infection.

8. Hantavirus Infection

Hantavirus infections can cause fever, fatigue, muscle aches, and bleeding, mimicking dengue hemorrhagic fever. However, hantavirus is often linked to contact with rodents, and respiratory or kidney issues may also develop. PCR testing is necessary to differentiate hantavirus from dengue.

9. Sepsis

Sepsis, a severe reaction to infection, can cause fever, confusion, low blood pressure, and sometimes a rash, which may resemble dengue shock syndrome. Blood cultures and other signs of infection help distinguish sepsis from dengue.

10. COVID-19

COVID-19 can present with fever, fatigue, headache, and muscle pain, which overlap with dengue symptoms. However, COVID-19 is often accompanied by respiratory symptoms such as cough, shortness of breath, and loss of taste or smell. PCR testing for COVID-19 is crucial to tell the two conditions apart.

VIRAL HAEMORRHAGIC FEVERS
Disease	Reservoir	Transmission	Incubation period	Geography	Mortality rate	Clinical features of severe disease
lassa fever	Multimammate rats (Mastomys natalensis)	Urine from rat Body fluids from patients	6–21 days	West Africa	15%	Haemorrhage, shock, encephalopathy, ARDS (responds to ribavirin) Deafness in survivors
Ebola fever	Undefined (?bats)	Body fluids from patients Handling infected primates	2–21 days	Central Africa Outbreaks as far north as Sudan	25–90%	Haemorrhage, hepatic and renal failure
marburg fever	Undefined	Body fluids from patients Handling infected primates	3–9 days	Central Africa Outbreak in Angola	25–90%	Haemorrhage, diarrhoea, encephalopathy, orchitis
Yellow fever	Monkeys	Mosquitoes	3–6 days	Tropical Africa, South and Central America	15%	Hepatic failure, renal failure, haemorrhage
Dengue	Humans	Aedes aegypti	2–7 days	Tropical and subtropical coasts; Asia, Africa, Americas	< 10%	Haemorrhage, shock
Crimean–Congo haemorrhagic fever	Small vertebrates Domestic and wild animals	Ixodes tick Body fluids	1–3 days up to 9 days 3–6 days up to 13 days	Africa, Asia, Eastern Europe	30%	Encephalopathy, haemorrhage, hepatic or renal failure, ARDS
Rift Valley fever	Domestic livestock	Contact with animals, mosquito or other insect bites	2–6 days	Africa, Arabian peninsular	1%	Haemorrhage, blindness, meningoencephalitis (complications only in a minority)
Kyasanur fever	Monkeys	Ticks	3–8 days	Karnataka State, India	5–10%	Haemorrhage, pulmonary oedema, neurological features Iridokeratitis in survivors
Bolivian and argentinian haemorrhagic fever (Junin and machupo viruses)	Rodents (Calomys spp.)	Urine, aerosols Body fluids from case (rare)	5–19 days (3–6 days for parenteral	South America	15–30%	Haemorrhage, shock, cerebellar signs (may respond to ribavirin)
haemorrhagic fever with renal syndrome (hantaan fever)	Rodents	Aerosols from faeces	5–42 days (typically 14 days)	Northern Asia, northern Europe, Balkans	5%	Acute renal impairment, cerebrovascular accidents, pulmonary oedema, shock (hepatic failure and haemorrhagic features only in some variants)

Conclusion

Because dengue shares symptoms with many other illnesses, a thorough medical history, physical examination, and the right laboratory tests are essential to make an accurate diagnosis. Identifying dengue early and distinguishing it from other diseases ensures proper treatment and helps avoid serious complications.

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