Arboviruses (dengue, Zika, chikungunya) US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Arboviruses (dengue, Zika, chikungunya). These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Arboviruses (dengue, Zika, chikungunya) US Medical PG Question 1: A 45-year-old man with a history of poorly controlled human immunodeficiency virus (HIV) infection presents to the emergency room complaining of clumsiness and weakness. He reports a 3-month history of worsening balance, asymmetric muscle weakness, and speech difficulties. He recently returned from a trip to Guatemala to visit his family. He has been poorly compliant with his anti-retroviral therapy and his most recent CD4 count was 195. His history is also notable for rheumatoid arthritis and hepatitis C. His temperature is 99°F (37.2°C), blood pressure is 140/90 mmHg, pulse is 95/min, and respirations are 18/min. On exam, he has 4/5 strength in his right upper extremity, 5/5 strength in his left upper extremity, 5/5 strength in his right lower extremity, and 3/5 strength in his left lower extremity. His speech is disjointed with intermittent long pauses between words. Vision is 20/100 in the left eye and 20/40 in his right eye; previously, his eyesight was 20/30 bilaterally. This patient most likely has a condition caused by which of the following types of pathogens?
- A. Arenavirus
- B. Bunyavirus
- C. Herpesvirus
- D. Polyomavirus (Correct Answer)
- E. Picornavirus
Arboviruses (dengue, Zika, chikungunya) Explanation: ***Polyomavirus***
- The patient's **poorly controlled HIV**, **low CD4 count (195)**, and progressive neurological symptoms (clumsiness, weakness, speech difficulties, vision changes) are highly suggestive of **Progressive Multifocal Leukoencephalopathy (PML)**.
- PML is caused by the **JC virus**, which is a type of **polyomavirus**, typically reactivating in immunocompromised individuals.
*Arenavirus*
- Arenaviruses (e.g., Lassa fever virus) are known to cause **hemorrhagic fevers** and can lead to neurological complications, but the clinical presentation described (progressive focal neurological deficits in an HIV patient) is not typical for an arenavirus infection.
- While some arenaviruses cause **meningoencephalitis**, the progressive, demyelinating-like course seen in this patient points away from arenavirus.
*Bunyavirus*
- Bunyaviruses (e.g., Hantavirus, La Crosse encephalitis virus) can cause **encephalitis**, fever, and myalgia, but they don't typically present with the specific constellation of **progressive white matter lesions** and focal neurological signs characteristic of PML in an HIV patient.
- Hantaviruses are more associated with **hemorrhagic fever with renal syndrome** or **hantavirus cardiopulmonary syndrome**.
*Herpesvirus*
- While herpesviruses (e.g., HSV, CMV, VZV) can cause severe neurological disease in HIV patients (e.g., **CMV encephalitis**, **HSV encephalitis**, **VZV vasculopathy**), the described progressive multifocal deficits, especially with rapid worsening, in an HIV patient with a low CD4 count strongly favor PML.
- Herpesviral encephalitides often present with more acute onset, fever, and seizures, or specific radiographic patterns not directly matching PML.
*Picornavirus*
- Picornaviruses, such as enteroviruses, can cause **aseptic meningitis** or **encephalitis**, particularly in immunocompromised individuals.
- However, the progressive, multifocal neurological deficits, particularly affecting **white matter**, are not characteristic of picornavirus infections, which tend to cause more diffuse or acute inflammatory processes.
Arboviruses (dengue, Zika, chikungunya) US Medical PG Question 2: A 30-year-old forest landscape specialist is brought to the emergency department with hematemesis and confusion. One week ago, she was diagnosed with influenza when she had fevers, severe headaches, myalgias, hip and shoulder pain, and a maculopapular rash. After a day of relative remission, she developed abdominal pain, vomiting, and diarrhea. A single episode of hematemesis occurred prior to admission. Two weeks ago she visited rainforests and caves in western Africa where she had direct contact with animals, including apes. She has no history of serious illnesses or use of medications. She is restless and her temperature is 38.0°C (100.4°F); pulse, 95/min; respirations, 20/min; and supine and upright blood pressure, 130/70 mm Hg and 100/65 mm Hg, respectively. Conjunctival suffusion is seen. Ecchymoses are observed on the lower extremities. She is bleeding from one of her intravenous lines. The peripheral blood smear is negative for organisms. The laboratory studies show the following:
Hemoglobin 10 g/dL
Leukocyte count 1,000/mm3
Segmented neutrophils 65%
Lymphocytes 20%
Platelet count 50,000/mm3
Partial thromboplastin time (activated) 60 seconds
Prothrombin time 25 seconds
Fibrin split products positive
Serum
Alanine aminotransferase (ALT) 85 U/L
Aspartate aminotransferase (AST) 120 U/L
γ-Glutamyltransferase (GGT) 83 U/L (N = 5–50 U/L)
Creatinine 2 mg/dL
Which of the following is the most likely causal pathogen?
- A. Zika virus
- B. Plasmodium falciparum
- C. Yersinia pestis
- D. Babesia microti
- E. Ebola virus (Correct Answer)
Arboviruses (dengue, Zika, chikungunya) Explanation: ***Ebola virus***
- The patient's presentation with **fever, myalgias, headache, maculopapular rash, gastrointestinal symptoms (vomiting, diarrhea, hematemesis), confusion, bleeding diathesis (ecchymoses, IV site bleeding, prolonged PT/aPTT, positive fibrin split products)**, and recent travel to **rainforests and caves in western Africa with ape contact** is highly consistent with Ebola virus disease.
- Laboratory findings of **leukopenia, thrombocytopenia, elevated liver enzymes (ALT, AST, GGT), and acute kidney injury (creatinine 2 mg/dL)** further support this diagnosis, as Ebola can cause widespread organ damage and disseminated intravascular coagulation (DIC).
*Zika virus*
- While Zika can cause **fever, rash, and arthralgia**, it typically presents as a milder illness and does not characteristically lead to severe **hemorrhagic manifestations, confusion, or significant organ dysfunction** like the patient's presentation.
- The patient's severe gastrointestinal symptoms, profound coagulopathy, and significant organ involvement are not typical features of Zika virus infection.
*Plasmodium falciparum*
- **Malaria** caused by *Plasmodium falciparum* can lead to **fever, headache, myalgias, and confusion**, and severe malaria can cause **anemia and thrombocytopenia**.
- However, the prominent **maculopapular rash, severe hemorrhagic diathesis with multi-site bleeding, prolonged PT/aPTT, and significant leukopenia** are not characteristic features of *P. falciparum* malaria, and the peripheral blood smear was negative for organisms.
*Yersinia pestis*
- **Bubonic plague** (caused by *Yersinia pestis*) can cause **fever, headache, and severe illness**, often with characteristic **lymphadenopathy (buboes)**, and can progress to pneumonic or septicemic forms.
- The absence of prominent buboes and the specific constellation of hemorrhagic fever symptoms, rash, and liver/kidney involvement point away from *Yersinia pestis* and more towards a viral hemorrhagic fever.
*Babesia microti*
- **Babesiosis** is a tick-borne illness causing **fever, fatigue, myalgias, and hemolytic anemia**, primarily seen in immunocompromised individuals or those with splenectomy, and does not typically involve **maculopapular rash, severe hemorrhagic phenomena, or significant leukopenia**.
- While it can cause some anemia and thrombocytopenia, the overall clinical picture, especially the prominent bleeding and multi-organ failure, is inconsistent with babesiosis.
Arboviruses (dengue, Zika, chikungunya) US Medical PG Question 3: A 13-year-old girl is brought to the physician because of worsening fever, headache, photophobia, and nausea for 2 days. One week ago, she returned from summer camp. She has received all age-appropriate immunizations. Her temperature is 39.1°C (102.3°F). She is oriented to person, place, and time. Physical examination shows a maculopapular rash. There is rigidity of the neck; forced flexion of the neck results in involuntary flexion of the knees and hips. Cerebrospinal fluid studies show:
Opening pressure 120 mm H2O
Appearance Clear
Protein 47 mg/dL
Glucose 68 mg/dL
White cell count 280/mm3
Segmented neutrophils 15%
Lymphocytes 85%
Which of the following is the most likely causal organism?
- A. Echovirus (Correct Answer)
- B. Listeria monocytogenes
- C. Streptococcus pneumoniae
- D. Herpes simplex virus
- E. Neisseria meningitidis
Arboviruses (dengue, Zika, chikungunya) Explanation: ***Echovirus***
- The patient's symptoms (fever, headache, photophobia, maculopapular rash, neck rigidity) along with CSF findings of **lymphocytic pleocytosis**, **normal glucose**, and **moderately elevated protein** are highly suggestive of **aseptic meningitis**.
- **Enteroviruses**, such as Echovirus, are the most common cause of **viral (aseptic) meningitis**, especially in children and during summer months, fitting the patient's age and recent summer camp attendance.
*Listeria monocytogenes*
- This organism typically causes meningitis in **neonates, elderly, or immunocompromised individuals**, which does not fit this healthy 13-year-old girl.
- While it can cause lymphocytic pleocytosis, it is less likely given the patient's age and presentation.
*Streptococcus pneumoniae*
- This is a common cause of **bacterial meningitis**, characterized by **PMN predominance (neutrophilic pleocytosis)**, **low CSF glucose**, and **markedly elevated CSF protein**, which are not seen in this case.
- The patient is also described as having received all age-appropriate immunizations, likely including the pneumococcal vaccine.
*Herpes simplex virus*
- HSV can cause aseptic meningitis or encephalitis, but it often presents with **focal neurological deficits** or **seizures** in cases of encephalitis, which are absent here.
- While it can cause lymphocytic pleocytosis, the maculopapular rash is less typical for HSV meningitis compared to enteroviruses.
*Neisseria meningitidis*
- This typically causes **bacterial meningitis** with characteristic CSF findings of **neutrophilic pleocytosis**, **low glucose**, and **high protein**.
- Although it can cause a rash (petechial or purpuric), the CSF profile and absence of petechiae make bacterial meningitis less likely.
Arboviruses (dengue, Zika, chikungunya) US Medical PG Question 4: A previously healthy 5-year-old boy is brought to the physician because of increasing weakness and a retroauricular rash that started 2 days ago. The rash spread rapidly and involves the trunk and extremities. Last week, he had a mild sore throat, pink eyes, and a headache. His family recently immigrated from Ethiopia. His immunization status is unknown. The patient appears severely ill. His temperature is 38.5°C (101.3°F). Examination shows tender postauricular and suboccipital lymphadenopathy. There is a nonconfluent, maculopapular rash over the torso and extremities. Infection with which of the following is the most likely cause of this patient's symptoms?
- A. Togavirus (Correct Answer)
- B. Human herpesvirus 6
- C. Parvovirus
- D. Varicella zoster virus
- E. Paramyxovirus
Arboviruses (dengue, Zika, chikungunya) Explanation: ***Togavirus***
- This patient's presentation is classic for **rubella** (German measles), caused by the **rubella virus**, a **togavirus**.
- The hallmark clinical finding is **tender postauricular and suboccipital lymphadenopathy**, which appears before the rash and is pathognomonic for rubella.
- The **maculopapular rash** begins on the face (retroauricular region) and spreads cephalocaudally to the trunk and extremities over 2-3 days.
- The prodrome includes **mild symptoms** (low-grade fever, sore throat, mild conjunctivitis, headache), which is characteristic of rubella.
- The patient's **unknown immunization status** and immigration from a region with lower vaccination coverage increases the likelihood of rubella infection.
*Paramyxovirus*
- **Measles virus** is a paramyxovirus that causes rubeola, but the clinical presentation differs significantly from this case.
- Measles typically presents with the **"3 Cs"**: severe **cough**, **coryza** (profuse nasal discharge), and **conjunctivitis** (more prominent than rubella).
- **Koplik spots** (white spots on buccal mucosa) are pathognomonic for measles and appear before the rash.
- Measles causes **higher fever** (often >40°C) and more severe systemic illness than described here.
- While measles can have lymphadenopathy, the **prominent postauricular and suboccipital nodes are characteristic of rubella, not measles**.
*Human herpesvirus 6*
- **HHV-6** causes **roseola infantum** (exanthem subitum), typically in infants 6-24 months old.
- The classic presentation is **high fever for 3-5 days** that suddenly resolves, followed immediately by a rash (**"fever then rash"**).
- This patient had prodromal symptoms followed by rash while still febrile, which does not fit roseola.
- Roseola does not cause significant lymphadenopathy or conjunctivitis.
*Parvovirus*
- **Parvovirus B19** causes **erythema infectiosum** (fifth disease), characterized by a **"slapped cheek"** facial erythema followed by a reticular (lacy) rash on the trunk and extremities.
- The rash pattern and prominent lymphadenopathy in this case are not consistent with fifth disease.
- Fifth disease typically causes mild or no fever and lacks the retroauricular distribution seen here.
*Varicella zoster virus*
- **VZV** causes **chickenpox**, which presents with a **pruritic, vesicular rash** that appears in successive crops and progresses through stages (macule → papule → vesicle → crust).
- This patient has a **maculopapular, nonconfluent rash** without vesicles, which is inconsistent with chickenpox.
- Chickenpox does not typically cause prominent postauricular lymphadenopathy.
Arboviruses (dengue, Zika, chikungunya) US Medical PG Question 5: A 13-year-old boy is brought to a physician with severe fevers and headaches for 3 days. The pain is constant and mainly behind the eyes. He has myalgias, nausea, vomiting, and a rash for one day. Last week, during an academic winter break, he traveled on a tour with his family to several countries, including Brazil, Panama, and Peru. They spent many evenings outdoors without any protection against insect bites. There is no history of contact with pets, serious illness, or use of medications. The temperature is 40.0℃ (104.0℉); the pulse is 110/min; the respiratory rate is 18/min, and the blood pressure is 110/60 mm Hg. A maculopapular rash is seen over the trunk and extremities. Several tender lymph nodes are palpated in the neck on both sides. A peripheral blood smear shows no organisms. Which of the following is most likely responsible for this patient’s presentation?
- A. Chagas disease
- B. Zika virus
- C. Babesiosis
- D. Malaria
- E. Dengue fever (Correct Answer)
Arboviruses (dengue, Zika, chikungunya) Explanation: ***Dengue fever***
- This patient's symptoms (fever, **retro-orbital headache**, myalgias, nausea, vomiting, rash, and travel history to endemic areas like **Brazil, Panama, and Peru**) are classic for dengue fever. The **high fever (40°C)** and rash are also highly suggestive.
- Exposure to mosquito bites in tropical regions, typical of travel during an academic break, is a common mode of transmission for this **flavivirus**.
*Chagas disease*
- Chagas disease, caused by **Trypanosoma cruzi**, is typically transmitted by the **reduviid bug** (kissing bug).
- Acute symptoms can include **fever**, **Romana's sign** (unilateral periorbital swelling), and sometimes a chagoma, but the widespread **maculopapular rash** and severe retro-orbital headache are less characteristic.
*Zika virus*
- Zika virus infection can present with **fever**, **rash**, **arthralgia**, and **conjunctivitis**.
- While the travel history fits, the **severe retro-orbital headache**, high fever, and myalgias are more prominent in dengue fever; Zika symptoms are generally milder in adults.
*Babesiosis*
- Babesiosis is a **tick-borne** illness caused by **Babesia parasites**, often presenting with **fever**, **fatigue**, chills, and **hemolytic anemia**.
- There is no mention of tick exposure, and the characteristic rash and retro-orbital headache are not typical features of babesiosis.
*Malaria*
- Malaria, caused by **Plasmodium parasites** transmitted by **Anopheles mosquitoes**, presents with cyclical fevers, chills, sweats, and fatigue.
- While the travel history to endemic areas is relevant, the **retro-orbital headache** and **maculopapular rash** as described are not typical for uncomplicated malaria; malaria is also detected on a peripheral blood smear, which was negative here.
Arboviruses (dengue, Zika, chikungunya) US Medical PG Question 6: A 26-year-old woman seeks evaluation at an urgent care clinic with complaints of fever and generalized muscle and joint pain for the past 3 days. She also complains of nausea, but denies vomiting. She does not mention any past similar episodes. Her past medical history is unremarkable, but she returned to the United States 1 week ago after spending 2 weeks in southeast Asia doing charity work. She received all the recommended vaccines prior to traveling. The temperature is 40.0°C (104.0°F), the respirations are 15/min, the pulse is 107/min, and the blood pressure is 98/78 mm Hg. Physical examination shows mild gingival bleeding and a petechial rash over the trunk. Laboratory studies show the following:
Laboratory test
Leukocyte count 4,000/mm³
Platelet count 100,000/mm³
Partial thromboplastin time (activated) 45 seconds
Which of the following is the most likely cause of this patient’s condition?
- A. Dengue fever (Correct Answer)
- B. Leptospirosis
- C. Typhoid fever
- D. Yellow fever
- E. Ebola virus
Arboviruses (dengue, Zika, chikungunya) Explanation: ***Dengue fever***
- This patient presents with a classic constellation of symptoms including **high fever**, **myalgia**, **arthralgia** (break-bone fever), **nausea**, and **petechial rash**, along with **thrombocytopenia** and evidence of **hemorrhagic manifestations** (mild gingival bleeding, petechiae, and prolonged PTT due to thrombocytopenia). Recent travel to Southeast Asia, an endemic region, further supports this diagnosis.
- The combination of **fever**, **leukopenia**, **thrombocytopenia**, and **hemorrhagic signs** in a patient returning from an endemic area is highly suggestive of dengue fever.
*Leptospirosis*
- While leptospirosis can cause **fever**, **myalgia**, and **nausea**, it is typically associated with contact with **contaminated water** or animal urine and often presents with **conjunctival suffusion** and sometimes **renal or hepatic involvement**, which are not prominent here.
- **Thrombocytopenia** and **hemorrhagic manifestations** are less common or severe in typical leptospirosis compared to dengue.
*Typhoid fever*
- Typhoid fever is characterized by a **gradually escalating fever**, **relative bradycardia**, and often a **"rose spot" rash**, along with **gastrointestinal symptoms** like constipation or diarrhea.
- While leukopenia can occur, **thrombocytopenia** and **hemorrhagic signs** like petechiae and gingival bleeding are not typical features.
*Yellow fever*
- Yellow fever, though mosquito-borne and endemic in some tropical regions, typically presents with **jaundice** (hence "yellow" fever), **renal failure**, and more severe **hemorrhage** (black vomitus) in its toxic phase.
- The patient's symptoms are more consistent with dengue's milder hemorrhagic picture and lack the prominent liver and kidney involvement seen in yellow fever.
*Ebola virus*
- Ebola virus disease causes a severe **hemorrhagic fever** with rapid onset and high mortality, characterized by profound **multi-organ failure**, widespread **hemorrhage** (internal and external), and severe **gastrointestinal symptoms** (vomiting, diarrhea).
- The clinical presentation, while including fever and some hemorrhagic signs, is not as severe or rapidly progressing as typical Ebola, nor does it fit the travel epidemiology for this patient (Ebola is endemic to Central and West Africa, not Southeast Asia).
Arboviruses (dengue, Zika, chikungunya) US Medical PG Question 7: A 42-year-old man comes to his physician with a history of fever, non-bloody diarrhea, and headache for 10 days. He also complains of anorexia and abdominal pain. He returned from a trip to India 3 weeks ago. His temperature is 40.0°C (104.0°F), pulse is 65/min, respirations are 15/min, and blood pressure is 135/80 mm Hg. He has developed a blanchable rash on his chest and trunk. A photograph of the rash is shown. Examination of the heart, lungs, and abdomen show no abnormalities. Laboratory studies show:
Hemoglobin 15 g/dL
Mean corpuscular volume 95 μm3
White blood cell count 3400/mm3
Percent segmented neutrophils 40%
Which of the following is the most likely diagnosis?
- A. Leptospirosis
- B. Enteric fever (Correct Answer)
- C. Dengue fever
- D. Malaria
- E. Nontyphoidal salmonellosis
Arboviruses (dengue, Zika, chikungunya) Explanation: ***Enteric fever***
- The constellation of **fever**, **non-bloody diarrhea**, **bradycardia** (pulse 65/min with 40°C fever), **leukopenia** (WBC 3400/mm³), **rose spots** (blanchable rash on chest/trunk), and recent travel to **India** (endemic area) is highly characteristic of enteric fever caused by *Salmonella Typhi* or *Paratyphi*.
- Abdominal pain, anorexia, and headache are also common symptoms, and the relatively low **neutrophil percentage** (40%) further supports the diagnosis of a bacterial infection with atypical white blood cell response.
*Leptospirosis*
- While leptospirosis can cause **fever** and **headache** and is found in tropical regions, it typically presents with **conjunctival suffusion**, **muscle pain**, and sometimes **jaundice** or **renal involvement**, none of which are detailed here.
- Exposure usually involves contact with contaminated water or soil, and **diarrhea** is less common than in enteric fever.
*Dengue fever*
- Dengue fever is characterized by **high fever**, severe **myalgia** and **arthralgia** ("breakbone fever"), and often a **maculopapular rash**, but **bradycardia** and **leukopenia** with low neutrophils are not typical features.
- **Hemorrhagic manifestations** are also a concern in severe dengue, which are not described.
*Malaria*
- Malaria presents with cyclical **fever** (often paroxysmal), **chills**, **sweats**, and frequently causes **anemia** and **thrombocytopenia**.
- While **leukopenia** can occur, the presence of **rose spots** and sustained fever with relative **bradycardia** point away from malaria as the primary diagnosis.
*Nontyphoidal salmonellosis*
- This typically causes **gastroenteritis** with **diarrhea**, **vomiting**, and **fever**, which is usually self-limiting.
- It would not typically present with **rose spots**, pronounced **bradycardia**, or a prolonged course with systemic symptoms suggestive of enteric fever.
Arboviruses (dengue, Zika, chikungunya) US Medical PG Question 8: A previously healthy 25-year-old man comes to the physician because of a 4-day history of fever, joint and body pain, diffuse headache, and pain behind the eyes. This morning he noticed that his gums bled when he brushed his teeth. He returned from a backpacking trip to the Philippines 4 days ago. His temperature is 39.4°C (103.0°F). Physical examination shows a diffuse maculopapular rash. His leukocyte count is 3,200/mm3 and platelet count is 89,000/mm3. Further evaluation shows increased serum levels of a flavivirus. Which of the following is the most likely causal pathogen?
- A. Dengue virus (Correct Answer)
- B. Ebola virus
- C. Chikungunya virus
- D. Lassa virus
- E. Hantavirus
Arboviruses (dengue, Zika, chikungunya) Explanation: ***Dengue virus***
- The patient's symptoms (fever, joint/body pain, headache, **retro-orbital pain**, maculopapular rash, **thrombocytopenia**, **leukopenia**, and **gum bleeding**) are classic for **dengue fever**, especially with recent travel to an endemic area like the **Philippines**.
- **Dengue** is a **flavivirus** transmitted by *Aedes aegypti* mosquitoes, and the clinical picture, including hemorrhagic manifestations and positive flavivirus test, strongly points to this diagnosis.
- Importantly, the laboratory finding of **increased serum flavivirus levels definitively identifies this as dengue**, as none of the other options are flaviviruses.
*Ebola virus*
- **Ebola is a filovirus, not a flavivirus**, which excludes it based on the laboratory findings.
- While Ebola causes hemorrhagic fever, it typically presents with more severe symptoms, including **profuse vomiting, diarrhea, and widespread internal and external bleeding**, which are not described in this case.
*Chikungunya virus*
- **Chikungunya is an alphavirus, not a flavivirus**, which excludes it based on the laboratory findings.
- **Chikungunya** also causes fever, rash, and joint pain, but is distinguished by more prominent and often **debilitating arthralgia** that can be chronic.
- **Hemorrhagic manifestations** like gum bleeding and severe thrombocytopenia are uncommon with Chikungunya and are more characteristic of dengue.
*Lassa virus*
- **Lassa is an arenavirus, not a flavivirus**, which excludes it based on the laboratory findings.
- **Lassa fever** is endemic to West Africa and presents with a gradual onset of fever, malaise, headache, and atypical rash, progressing to more severe manifestations like **facial edema** and **hemorrhage**.
- The geographic exposure (Philippines) does not align with Lassa virus endemicity.
*Hantavirus*
- **Hantavirus is a bunyavirus, not a flavivirus**, which excludes it based on the laboratory findings.
- **Hantavirus infections** can cause two main syndromes: **Hantavirus Pulmonary Syndrome (HPS)** with severe respiratory distress, or **Hemorrhagic Fever with Renal Syndrome (HFRS)**, which involves kidney failure and hemorrhagic manifestations.
- The patient's symptoms of retro-orbital pain, prominent rash, and specific lab findings (leukopenia, thrombocytopenia) are not typical for hantavirus, and there is no mention of severe respiratory or renal involvement.
Arboviruses (dengue, Zika, chikungunya) US Medical PG Question 9: A 38-year-old man presents to the physician with fever and malaise for 4 days. He has headaches and joint pain. A pruritic rash appeared on the trunk yesterday. He had blood in his ejaculate twice. His hearing has become partially impaired. There is no history of serious illnesses or the use of medications. Ten days ago, he traveled to Brazil where he spent most of the time outdoors in the evenings. He did not use any control measures for mosquito bites. His temperature is 38.2℃ (100.8℉); the pulse is 88/min; the respiratory rate is 13/min, and the blood pressure is 125/60 mm Hg. Conjunctival suffusion is noted. A maculopapular rash is present over the trunk and proximal extremities without the involvement of the palms or soles. Several joints of the hands are tender to palpation. The abdomen is soft with no organomegaly. A peripheral blood smear shows no pathogenic organisms. Which of the following is the most likely diagnosis?
- A. Rocky Mountain spotted fever
- B. Chagas disease
- C. Whipple’s disease
- D. Zika virus disease (Correct Answer)
- E. Malaria
Arboviruses (dengue, Zika, chikungunya) Explanation: ***Zika virus disease***
- The patient's travel to **Brazil**, **mosquito exposure**, fever, malaise, headache, arthralgia, and **maculopapular rash** (without palm/sole involvement) are classic symptoms of Zika virus.
- Additional findings like **conjunctival suffusion**, **hematospermia**, and **hearing impairment** are consistent with atypical presentations or complications of Zika.
*Rocky Mountain spotted fever*
- While it presents with fever, headache, and rash, the rash typically involves the **palms and soles** and can be **petechial**, which is not described.
- This disease is common in the **southeastern and south-central US**, not typically Brazil, and is transmitted by ticks, not mosquitoes.
*Chagas disease*
- This is a parasitic disease (Trypanosoma cruzi) transmitted by **reduviid bugs** (kissing bugs) in Central and South America.
- Acute symptoms often include a **chagoma** (local swelling at the bite site) or **Romaña's sign** (periorbital swelling), followed by chronic cardiac or gastrointestinal involvement, which don't fit the current presentation.
*Whipple’s disease*
- This rare systemic bacterial infection (Tropheryma whipplei) primarily affects the **gastrointestinal tract**, leading to malabsorption, diarrhea, and weight loss.
- While it can cause arthralgia, fever, and neurological symptoms, the prominent rash, conjunctival suffusion, and recent travel/mosquito exposure are not characteristic.
*Malaria*
- Malaria presents with cyclical **fevers** and **chills**, headache, and myalgia, often with **anemia** and **splenomegaly**.
- A **rash is uncommon** in malaria, and the other specific symptoms like conjunctival suffusion, hematospermia, and hearing impairment are not typical.
Arboviruses (dengue, Zika, chikungunya) US Medical PG Question 10: A 53-year-old man presents to an urgent care center with severe fever that began during the day along with muscle and joint pains. He states that he felt fine the day before but then developed a fever to 103°F (39.4°C) and had to leave work after which he developed a headache and body pains. The patient states that he was recently in South Asia for a business trip and was otherwise feeling well since returning 2 weeks ago. On exam, the patient’s temperature is 103.3°F (39.6°C), blood pressure is 110/84 mmHg, pulse is 94/min, and respirations are 14/min. On physical exam, the patient appears flushed and has a rash that blanches when touched. On laboratory workup, the pathogen was identified as an enveloped virus with an icosahedral capsid and had positive-sense, single-stranded linear RNA. Which of the following is the most likely cause of this patient's presentation?
- A. Dengue virus (Correct Answer)
- B. Norovirus
- C. Coronavirus
- D. Marburg virus
- E. Saint Louis encephalitis virus
Arboviruses (dengue, Zika, chikungunya) Explanation: ***Dengue virus***
- The patient's presentation with **acute onset of high fever**, severe **muscle and joint pains** ("breakbone fever"), headache, and a **blanching rash** after recent travel to **South Asia** is highly characteristic of dengue fever.
- The description of the pathogen as an **enveloped virus** with an **icosahedral capsid** and **positive-sense, single-stranded linear RNA** perfectly matches the **Flaviviridae family** to which the dengue virus belongs.
- Among the options, only dengue virus and Saint Louis encephalitis virus have these exact structural characteristics (both are flaviviruses), but the **clinical presentation** with severe myalgia/arthralgia and travel to South Asia clearly points to dengue.
*Norovirus*
- Norovirus typically causes **gastroenteritis**, characterized primarily by **vomiting, diarrhea**, and abdominal cramps, which are not the dominant symptoms in this patient.
- While fever can occur, it's usually **mild** and not as prominent as the high fever and severe myalgia/arthralgia seen in dengue.
- **Structurally**, norovirus is **non-enveloped** (naked capsid), which does not match the pathogen description.
*Coronavirus*
- Coronaviruses are associated with **respiratory illnesses** (e.g., common cold, SARS, MERS, COVID-19) causing symptoms like cough, shortness of breath, and sore throat.
- While fever and body aches can occur, the **severe joint pains** and typical rash are not hallmarks of coronavirus infections.
- **Structurally**, coronaviruses have **helical nucleocapsid symmetry**, not icosahedral, which excludes this option based on the pathogen description.
*Marburg virus*
- Marburg virus causes a severe **hemorrhagic fever** with symptoms including high fever, severe headache, malaise, followed by gastrointestinal symptoms, and eventually **hemorrhagic manifestations** (e.g., bleeding from orifices, petechiae, purpura).
- The patient's presentation does not describe any hemorrhagic signs, and the rash is blanching, not petechial or purpuric.
- **Structurally**, Marburg is a filovirus with **helical symmetry** and **negative-sense ssRNA**, not positive-sense with icosahedral capsid, which excludes this option.
*Saint Louis encephalitis virus*
- Saint Louis encephalitis virus causes a **neuroinvasive disease** characterized by encephalitis, presenting with altered mental status, seizures, and focal neurological deficits, although some patients may have milder fever and headache.
- While it shares the **same viral structure** as dengue (both are flaviviruses with enveloped, icosahedral, (+)ssRNA), the **clinical presentation** differs significantly—this patient lacks neurological symptoms.
- The prominent **severe myalgia, arthralgia**, typical blanching rash, and **travel history to dengue-endemic South Asia** distinguish dengue from Saint Louis encephalitis.
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