Dengue virus infection
Dengue is a flavivirus spread by daytime-feeding Aedes mosquitoes that causes an acute febrile illness with retro-orbital pain and severe myalgia, and can progress to hemorrhagic fever and shock, especially on heterotypic secondary infection; management is supportive with acetaminophen and fluids, avoiding NSAIDs and aspirin.
- Topic reviewThe full article, organized the way the exam asks it.
- ABIM-format MCQsVignettes with an explanation for every wrong answer.
- Key factsThe numbers and thresholds worth memorizing, up front.
- AI tutorMedBrain answers the question you're stuck on.
What this article covers
- Overview
Flavivirus spread by Aedes mosquitoes: dengue virus is transmitted by daytime-feeding Aedes species mosquitoes, the same vector that carries chikungunya and Zika virus, and their clinical presentations overlap substantially.
- Epidemiology
Most common cause of fever in travelers returning from South America: dengue outranks other arboviral and parasitic causes of fever in this population.
- Risk factors
Travel to or residence in an endemic area: the dominant risk factor, particularly during local outbreak periods.
- Pathophysiology
Direct viral infection of the bloodstream (viremia): virus disseminates hematogenously after the mosquito bite, producing the initial febrile, myalgic illness.
- Clinical features
Abrupt onset of high fever with chills: the presenting feature, often with a biphasic ("saddleback") pattern in which fever resolves after 5 to 7 days and then mildly returns.
- Differential diagnosis
Chikungunya fever: shares fever, headache, myalgia, and rash, but produces severe bilateral, symmetric polyarthralgia with joint swelling that is far more prominent than in dengue, and hemorrhagic manifestations are uncommon.
- Diagnosis
Dengue is confirmed by serology (IgM and IgG) or reverse transcriptase polymerase chain reaction (RT-PCR); disease is staged clinically as dengue fever, dengue hemorrhagic fever (fever plus…
- Management
First, treat as outpatient supportive care in uncomplicated illness: oral rehydration and antipyresis with acetaminophen 650 mg PO every 6 hours as needed (maximum 3,000 mg/day) through the febrile phase, typically 5 to 7 days.
- Complications
Dengue shock syndrome: plasma leakage progressing to circulatory collapse; the most feared complication and a major driver of mortality.
- Prognosis
Primary infection is typically self-limited: fever resolves after 5 to 7 days, often with a brief second febrile period (saddleback pattern), and most travelers recover fully with supportive care.
- Prevention
Mosquito avoidance is the primary preventive measure: use EPA-registered insect repellent, wear protective clothing, and use screens or netting during daytime hours when Aedes mosquitoes feed…
Read the whole article
Subscribing to Internal Medicine opens every article, the full question bank and MedBrain, on the web, iPhone and Android.
Related articles
- Chikungunya fever
Chikungunya is an Aedes mosquito-borne alphavirus causing abrupt high fever and severe, often symmetric, small-joint polyarthralgia that closely mimics dengue fever but is distinguished by more prominent and frequently relapsing joint disease. Diagnosis relies on serology or reverse transcriptase PCR, no antiviral or vaccine-based prevention is in routine use, and treatment is symptomatic with dengue excluded before using NSAIDs because of bleeding risk.
- Zika virus infection
Zika virus is an Aedes-transmitted flavivirus causing a usually mild febrile illness with rash and conjunctivitis, but infection during pregnancy can cross the placenta and cause congenital Zika syndrome with microcephaly, and postinfectious Guillain-Barre syndrome is a recognized complication. Diagnosis uses RT-PCR in the first 2 weeks of illness and IgM serology thereafter, treatment is supportive, and prevention centers on avoiding travel to endemic areas during pregnancy and preventing sexual transmission.
- Malaria
Malaria is a Plasmodium infection acquired from Anopheles mosquito bites, most often diagnosed in returning travelers from sub-Saharan Africa, and severe Plasmodium falciparum disease is a medical emergency treated with IV artesunate.
- Leptospirosis
Leptospirosis is a zoonotic spirochetal infection from water or soil contaminated with infected-animal urine, causing a biphasic illness with conjunctival suffusion and calf/lumbar myalgia, occasionally progressing to Weil disease with jaundice and renal failure, diagnosed clinically and confirmed by culture, serology, or PCR, and treated with doxycycline or, in severe disease, IV penicillin or ceftriaxone.
- Measles
Measles (rubeola) is a highly contagious paramyxovirus infection that has re-emerged in the United States because of low vaccination rates, presenting with a prodrome of the 4 C's followed by a cephalocaudal maculopapular rash, confirmed by PCR or IgM, and managed with supportive care plus vitamin A.
- Hepatitis A virus infection
Hepatitis A virus is a fecal-oral RNA virus that causes acute, host-immune-mediated hepatitis with a prodrome followed by jaundice, aminotransferases often exceeding 1,000 U/L, and full recovery in at least 90% of patients within 3 to 6 months. Diagnosis rests on HAV IgM, treatment is supportive, and prevention centers on a 2-dose inactivated vaccine plus prompt postexposure prophylaxis.
- Rocky Mountain spotted fever
Rocky Mountain spotted fever is the most common and most severe spotted fever rickettsiosis in the United States, caused by Rickettsia rickettsii and transmitted by the dog tick. The hallmark petechial rash typically lags days behind fever onset, so empiric doxycycline must be started on clinical suspicion alone, since treatment delay drives the disease's disproportionate mortality.
- West Nile virus infection
West Nile virus (WNV) is a mosquito-borne flavivirus and the most common cause of epidemic viral encephalitis in the United States, transmitted by Culex mosquitoes between June and October. Most infections are asymptomatic, but neuroinvasive disease can present as meningitis, encephalitis with basal ganglia involvement (tremor, parkinsonism, myoclonus), or acute flaccid paralysis resembling poliomyelitis; diagnosis is by WNV IgM in serum or CSF, and treatment is supportive because no specific antiviral or vaccine exists.