Hi all,
In light of it being summer, I figured I’d start out with a series of POTDs relevant to the season – mosquito borne diseases.
It’s always been kind of a black box for me keeping all of these straight as they tend to present very similar to each other. You may not see these very frequently, HOWEVER as Dr. Strayer kindly pointed out to me, there are record-breaking numbers of Dengue Fever in countries throughout the Americas this year, exceeding the highest number ever recorded in a single year. So, you might see it sooner than you think given our patient population.
For today, we’re going to focus on separating some very similar entities:
Dengue Fever
West Nile Virus
Chikungunya Fever
DENGUE FEVER
Dengue (break-bone fever) is a viral infection that spreads from mosquitoes (Aedes aegypti or Aedes albopictus) to people. It is more common in tropical and subtropical climates.
Dengue fever is the fastest-spreading mosquito-borne viral disease worldwide, affecting over 100 million people annually. This disease also leads to 20 to 25,000 deaths, primarily among children, and is prevalent in more than 100 countries. Epidemics occur yearly in the Americas, Asia, Africa, and Australia.
Traditionally, symptoms of the virus are divided into three phases:
Febrile Phase: During the febrile phase, individuals typically experience a sudden onset of high-grade fever, which usually lasts for 2 to 7 days. Associated symptoms during this phase include facial flushing, skin erythema, myalgias, arthralgias, headache, sore throat, conjunctival injection, anorexia, nausea, and vomiting.
Critical Phase: During the critical phase, defervescence marks a period when the temperature typically decreases to approximately 37.5-38 °C, occurring between days 3 and 7. This phase is associated with heightened capillary permeability, as well as a rapid decline in platelet count, accompanied by increased hematocrit levels and sometimes leukopenia. If left untreated, the critical phase can progress to shock, organ dysfunction, disseminated intravascular coagulation, or hemorrhage.
Recovery Phase: The recovery phase involves the gradual reabsorption of extravascular fluid over 2 to 3 days. During this period, patients often exhibit bradycardia.
The most common laboratory findings associated with Dengue are thrombocytopenia, leukopenia, and elevated levels of aspartate aminotransferase.
The virus antigen can be detected using enzyme-linked immunosorbent assay (ELISA) test, polymerase chain reaction (PCR), or by isolating the virus from body fluids.
TREATMENT:
Patients with more mild symptoms (i.e. no hemodynamic instability and minimal risk factors/comorbidities) can often be managed outpatient with oral antipyretics and oral hydration.
More severe symptoms require evaluation for hospitalization and should be started on IV crystalloids. Blood transfusion is indicated in cases of severe or suspected bleeding when the patient remains unstable despite adequate fluid resuscitation and hematocrit falls. Platelet transfusion may be necessary if the platelet count drops below 20,000 cells per microliter and there is a high risk of bleeding. Notably, it is essential to avoid administering aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), and other anticoagulants. No antiviral medications are recommended, and no laboratory tests can reliably predict the progression to severe disease.
WEST NILE VIRUS
West Nile Virus is another flavivirus (same as Dengue) that also spreads from mosquitoes (most commonly the Culex genus) to people.
Originally seen in Uganda and other parts of Africa, West Nile virus began showing up throughout Europe, Asia, and North America in the 1990s. It is now present throughout much of the world.
The incubation period of the West Nile virus varies from 4-14 days. Symptoms tend to last 5-7 days, however nearly 80% of those infected are asymptomatic!
In most cases, symptoms include myalgia, malaise, and a low-grade fever. Other associated symptoms may include headache, eye pain, vomiting, anorexia, and up to 50% may have a maculopapular rash on the trunk.
In rare cases, the virus can cause neurologic symptoms, including severe muscle weakness, changes in mental status, seizures, or flaccid paralysis. These patients initially present with features of encephalitis and/or meningitis that progresses rapidly, and they require ICU care.
Common laboratory findings include leukocytosis (NOTE THIS CAN HELP DIFFERENTIATE FROM DENGUE) and other nonspecific findings secondary to the viral infection. Hyponatremia may be seen when the CNS is involved, and this will typically have findings consistent with viral meningitis on lumbar puncture.
For neuroinvasive disease, the CSF should also be tested using the ELISA test.
TREATMENT:
Treatment of West Nile virus is primarily supportive care. Researchers have tried several agents including interferon, ribavirin, and intravenous immunoglobulin. No clear efficacy data exists as only one controlled study has been performed to date.
Individuals with milder cases can be managed symptomatically as outpatients and tend to have an excellent prognosis. However, toxic patients with neurologic symptoms usually require long-term ICU care.
CHIKUNGUNYA FEVER
Chikungunya is a togavirus that will spread from mosquitoes (Aedes aegypti or Aedes albopictus, same as Dengue) to humans.
First discovered in Tanzania in 1952, it has since spread, effectively reaching the Americas in 2013, Florida in July 2014, and severely affecting various Caribbean, Central, and South American countries after that.
Symptoms typically include (you guessed it) non-specific findings of high-grade fever and myalgia, following a 3 to 7 day incubation period, and lasting around 3 to 5 days. Bilateral symmetrical polyarthralgia ensues 2 to 5 days after the onset of fevers and preferentially involves distal over proximal joints.
Although it is not considered to be a neurotropic virus, it has long been associated with neurologic symptoms, with encephalitis among newborns infected through mother-to-child transmission being the most common.
Evaluation consists mainly of the clinical findings of fever and polyarthralgia in a person who recently returned from an affected region.
Diagnosis of CHIKV can be established or confirmed by detection of viral RNA with serology and/or reverse-transcription polymerase chain reaction (RT-PCR) depending on disease time frame of presentation.
TREATMENT:
Symptomatic relief is the mainstay treatment for Chikungunya fever, including adequate hydration, rest, and pain/fever relief preferably with acetaminophen. The WHO discourages the use of aspirin and most nonsteroidal anti-inflammatory drugs (NSAIDs) during the first 48 hours due to the risk of aggravating platelet dysfunction, especially in cases of possible DENV coinfection.
TL;DR
Dengue:
Spread by Aedes mosquitoes.
Thrombocytopenia, leukopenia, elevated LFTs.
High capillary permeability.
Supportive care, avoid ASA or NSAIDs due to low platelets.
West Nile Virus:
Spread by Culex mosquitoes.
Although rare, often associated with neurologic symptoms (encephalitis/meningitis).
Leukocytosis; hyponatremia in CNS disease.
Supportive care.
Chikungunya
Spread by Aedes mosquitoes.
Fever + polyarthralgia (bilateral symmetrical polyarthralgia, more commonly distal joints).
Supportive care, avoid ASA or NSAIDs due to risk of co-infection with Dengue.
Dengue:
https://www.ecdc.europa.eu/en/dengue-monthly
https://www.ncbi.nlm.nih.gov/books/NBK430732/
West Nile Virus:
https://www.who.int/news-room/fact-sheets/detail/west-nile-virus
https://www.ncbi.nlm.nih.gov/books/NBK544246/
https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(02)00368-7/abstract
Chikungunya:
https://www.ecdc.europa.eu/en/chikungunya-monthly
https://www.ncbi.nlm.nih.gov/books/NBK534224/
https://www.who.int/news-room/fact-sheets/detail/chikungunya