A 38-year-old man comes to the physician because of severe muscle pain and swelling of his eyelids for 3 days. He has also had fever and chills during this period. For the last 2 days, he has had severe pain in his mouth while chewing. He had an episode of diarrhea a month ago for which he did not seek medical care. He has no history of serious illness. His sister has dermatomyositis. He returned from a hunting trip to eastern Europe 45 days ago. His temperature is 38.1°C (100.6°F), pulse is 80/min, and blood pressure is 130/70 mm Hg. Examination shows periorbital edema and severe generalized muscle tenderness. There are splinter hemorrhages on both hands. Laboratory studies show:
Hemoglobin 14.2 g/dL
Leukocyte count 12,500/mm3
Segmented neutrophils 60%
Eosinophils 18%
Lymphocytes 20%
Monocytes 2%
Serum
Glucose 117 mg/dL
Creatinine 1.1 mg/dL
Alkaline phosphatase 72 U/L
Creatine kinase 765 U/L
Urinalysis is within normal limits. Which of the following is most likely to have prevented this patient's condition?
Q62
A 34-year-old woman presents with confusion, drowsiness, and headache. The patient’s husband says her symptoms began 2 days ago and have progressively worsened with an acute deterioration of her mental status 2 hours ago. The patient describes the headaches as severe, localized to the frontal and periorbital regions, and worse in the morning. Review of symptoms is significant for a mild, low-grade fever, fatigue, and nausea for the past week. Past medical history is significant for HIV infection for which she is not currently receiving therapy. Her CD4+ T cell count last month was 250/mm3. The blood pressure is 140/85 mm Hg, the pulse rate is 90/min, and the temperature is 37.7°C (100.0°F). On physical examination, the patient is conscious but drowsy. Papilledema is present. No pain is elicited with extension of the leg at the knee joint. The remainder of the physical examination is negative. Laboratory findings, including panculture, are ordered. A noncontrast CT scan of the head is negative and is followed by a lumbar puncture. CSF analysis is significant for:
Opening pressure 250 mm H2O (70-180 mm H2O)
Glucose 30 mg/dL (40-70 mg/dL)
Protein 100 mg/dL (<40 mg/dL)
Cell count 20/mm3 (0-5/mm3)
Which of the following additional findings would most likely be found in this patient?
Q63
A 28-year-old female in the 2nd trimester of pregnancy is diagnosed with primary Toxoplasma gondii infection. Her physician fears that the fetus may be infected in utero. Which of the following are associated with T. gondii infection in neonates?
Q64
A 31-year-old man comes to the physician because of severe muscle pain and fever for 4 days. He likes to go hunting and consumed bear meat 1 month ago. Examination shows periorbital edema and generalized muscle tenderness. His leukocyte count is 12,000/mm3 with 19% eosinophils. The release of major basic protein in response to this patient’s infection is most likely a result of which of the following?
Q65
A 17-year-old Latin American woman with no significant past medical history or family history presents to her pediatrician with concerns about several long-standing skin lesions. She notes that she has had a light-colored rash on her chest and abdomen that has been present for the last 2 years. The blood pressure is 111/81 mm Hg, pulse is 82/min, respiratory rate is 16/min, and temperature is 37.3°C (99.1°F). Physical examination reveals numerous hypopigmented macules over her chest and abdomen. No lesions are seen on her palms or soles. When questioned, she states that these lesions do not tan like the rest of her skin when exposed to the sun. The remainder of her review of systems is negative. What is the most likely cause of these lesions?
Q66
An 18-year-old man presents to the office, complaining of an itchy patch on his torso that appeared one week ago. The patient is on the college wrestling team and is concerned he will not be able to compete if it gets infected. He has no significant medical history, and his vital signs are within normal limits. On examination, there is an erythematous, scaly plaque with central clearing at approximately the level of rib 6 on the left side of his torso. What diagnostic test would be most appropriate at this time?
Q67
A 45-year-old man is transferred to the intensive care unit from the emergency department for acute respiratory failure. He was rushed to the hospital after developing progressive respiratory distress over the last 24 hours. His medical history is significant for long-standing severe persistent asthma, hypertension, and several bouts of community and hospital-acquired pneumonia. His medications include amlodipine, lisinopril, inhaled fluticasone, salmeterol, and oral prednisone. He is a lifelong non-smoker and drinks alcohol occasionally on the weekends. He works as a sales executive and went to Hawaii a month ago. In the emergency department, he was started on broad-spectrum antibiotics and bronchodilators. His respiratory failure progressively worsens, and on day 2 of admission, he requires mechanical ventilator support. Chest X-ray shows multiple nodules bilaterally in the lower lobes. Flexible bronchoscopy is performed and the bronchoalveolar lavage sample from the medial segment of the right lower lobe shows neutrophils, and the fungal preparation shows Aspergillus fumigatus. A video-assisted thoracoscopy is performed and biopsy from the right lower lobe is taken which shows plugging of the terminal bronchioles with mucus, inflammatory cells, and fungal vascular invasion. Which of the following is the most likely mechanism responsible for the biopsy findings?
Q68
A 27-year-old man presents to the emergency room with persistent fever, nausea, and vomiting for the past 3 days. While waiting to be seen, he quickly becomes disoriented and agitated. Upon examination, he has visible signs of difficulty breathing with copious oral secretions and generalized muscle twitching. The patient’s temperature is 104°F (40°C), blood pressure is 90/64 mmHg, pulse is 88/min, and respirations are 18/min with an oxygen saturation of 90% on room air. When the nurse tries to place a nasal cannula, the patient becomes fearful and combative. The patient is sedated and placed on mechanical ventilation. Which of the following is a risk factor for the patient’s most likely diagnosis?
Parasites/Fungi US Medical PG Practice Questions and MCQs
Question 61: A 38-year-old man comes to the physician because of severe muscle pain and swelling of his eyelids for 3 days. He has also had fever and chills during this period. For the last 2 days, he has had severe pain in his mouth while chewing. He had an episode of diarrhea a month ago for which he did not seek medical care. He has no history of serious illness. His sister has dermatomyositis. He returned from a hunting trip to eastern Europe 45 days ago. His temperature is 38.1°C (100.6°F), pulse is 80/min, and blood pressure is 130/70 mm Hg. Examination shows periorbital edema and severe generalized muscle tenderness. There are splinter hemorrhages on both hands. Laboratory studies show:
Hemoglobin 14.2 g/dL
Leukocyte count 12,500/mm3
Segmented neutrophils 60%
Eosinophils 18%
Lymphocytes 20%
Monocytes 2%
Serum
Glucose 117 mg/dL
Creatinine 1.1 mg/dL
Alkaline phosphatase 72 U/L
Creatine kinase 765 U/L
Urinalysis is within normal limits. Which of the following is most likely to have prevented this patient's condition?
A. Consume pasteurized dairy products
B. Clean drinking water
C. Cooking meat to 71°C (160°F) (Correct Answer)
D. Metronidazole at the onset of diarrhea
E. Influenza vaccine
Explanation: ***Cooking meat to 71°C (160°F)***
- This patient's symptoms (fever, **periorbital edema**, **severe myalgia**, **eosinophilia**, elevated CK) after a hunting trip to eastern Europe are highly suggestive of **Trichinellosis**, caused by consuming undercooked meat infected with *Trichinella* larvae.
- **Thoroughly cooking meat** (especially wild game or pork) to an internal temperature of 71°C (160°F) is a primary preventative measure against *Trichinella* infection, as it kills the larvae.
*Consume pasteurized dairy products*
- Consuming pasteurized dairy products prevents infections such as **brucellosis** or **listeriosis**.
- These infections typically present with different clinical features, and their transmission is not associated with hunting wild game in Eastern Europe in the context of the patient's symptoms.
*Clean drinking water*
- Access to clean drinking water is crucial for preventing waterborne diseases like **giardiasis**, **cholera**, or **typhoid fever**.
- While the patient had diarrhea, the subsequent systemic symptoms with muscle involvement and eosinophilia point away from typical waterborne illnesses as the primary cause of his current condition.
*Metronidazole at the onset of diarrhea*
- **Metronidazole** is an antibiotic used to treat parasitic infections like **Giardia** or bacterial infections such as those caused by *Clostridium difficile*.
- Treating diarrhea with metronidazole, even if effective for the initial gastrointestinal issue, would not prevent a subsequent *Trichinella* infection which is acquired through undercooked meat.
*Influenza vaccine*
- The **influenza vaccine** protects against the **influenza virus**, which causes respiratory symptoms, fever, and generalized myalgia.
- However, the absence of prominent respiratory symptoms, the presence of marked eosinophilia, periorbital edema, and the history of recent exposure to wild game make influenza an unlikely diagnosis.
Question 62: A 34-year-old woman presents with confusion, drowsiness, and headache. The patient’s husband says her symptoms began 2 days ago and have progressively worsened with an acute deterioration of her mental status 2 hours ago. The patient describes the headaches as severe, localized to the frontal and periorbital regions, and worse in the morning. Review of symptoms is significant for a mild, low-grade fever, fatigue, and nausea for the past week. Past medical history is significant for HIV infection for which she is not currently receiving therapy. Her CD4+ T cell count last month was 250/mm3. The blood pressure is 140/85 mm Hg, the pulse rate is 90/min, and the temperature is 37.7°C (100.0°F). On physical examination, the patient is conscious but drowsy. Papilledema is present. No pain is elicited with extension of the leg at the knee joint. The remainder of the physical examination is negative. Laboratory findings, including panculture, are ordered. A noncontrast CT scan of the head is negative and is followed by a lumbar puncture. CSF analysis is significant for:
Opening pressure 250 mm H2O (70-180 mm H2O)
Glucose 30 mg/dL (40-70 mg/dL)
Protein 100 mg/dL (<40 mg/dL)
Cell count 20/mm3 (0-5/mm3)
Which of the following additional findings would most likely be found in this patient?
A. Gram-positive diplococci are present on microscopy
B. CSF shows a positive acid-fast bacillus stain
C. Multiple ring-enhancing lesions are seen on a CT scan
D. CSF shows gram negative diplococci
E. CSF India ink stain shows encapsulated yeast cells (Correct Answer)
Explanation: ***CSF India ink stain shows encapsulated yeast cells***
- The patient's presentation with **subacute meningitis symptoms** (headache, confusion, low-grade fever) in the setting of **untreated HIV infection** with a low CD4+ count (250/mm3) strongly suggests an opportunistic infection.
- The CSF findings of **elevated opening pressure**, **low glucose**, **high protein**, and **moderate pleocytosis** are classic for **cryptococcal meningitis**, for which the India ink stain is diagnostic for encapsulated yeast cells.
*Gram-positive diplococci are present on microscopy*
- This finding suggests **bacterial meningitis**, specifically caused by organisms like *Streptococcus pneumoniae*.
- While bacterial meningitis presents acutely with severe symptoms, the **subacute course** and moderate pleocytosis are less typical, and the patient's immune status points towards an opportunistic infection.
*CSF shows a positive acid-fast bacillus stain*
- A positive **acid-fast bacillus (AFB) stain** in CSF would indicate **tuberculous meningitis**.
- While tuberculous meningitis can present subacutely with similar CSF findings in HIV patients, it typically involves a more significant lymphocytic pleocytosis and a more pronounced chronic course than suggested by the acute worsening.
*Multiple ring-enhancing lesions are seen on a CT scan*
- **Multiple ring-enhancing lesions** on CT or MRI are characteristic of **Toxoplasma encephalopathy** or **CNS lymphoma** in HIV-positive patients.
- While these are common HIV-related CNS complications, the patient's primary presentation points to **meningitis** (inflammation of meninges with CSF abnormalities) rather than focal brain lesions without meningeal involvement.
*CSF shows gram negative diplococci*
- **Gram-negative diplococci** in CSF suggest **meningococcal meningitis** (*Neisseria meningitidis*).
- This typically presents as an **acute, severe bacterial meningitis** with rapid deterioration, usually in immunocompetent individuals or specific outbreaks, which doesn't align with the subacute onset and specific CSF profile for cryptococcus.
Question 63: A 28-year-old female in the 2nd trimester of pregnancy is diagnosed with primary Toxoplasma gondii infection. Her physician fears that the fetus may be infected in utero. Which of the following are associated with T. gondii infection in neonates?
A. Hutchinson’s teeth, saddle nose, short maxilla
B. Deafness, seizures, petechial rash
C. Hydrocephalus, chorioretinitis, intracranial calcifications (Correct Answer)
D. Patent ductus arteriosus, cataracts, deafness
E. Temporal encephalitis, vesicular lesions
Explanation: ***Hydrocephalus, chorioretinitis, intracranial calcifications***
- These are the classic triad of symptoms (known as the **Sabin triad**) often associated with **congenital toxoplasmosis**.
- **Hydrocephalus** results from obstruction of cerebrospinal fluid flow, **chorioretinitis** can lead to vision loss, and **intracranial calcifications** are a hallmark of the infection's impact on the brain.
*Hutchinson’s teeth, saddle nose, short maxilla*
- These are characteristic features of **congenital syphilis**, not *Toxoplasma gondii* infection.
- **Hutchinson's triad** includes Hutchinson's teeth, interstitial keratitis, and sensorineural hearing loss in congenital syphilis.
*Deafness, seizures, petechial rash*
- While seizures can occur with severe congenital infections, this combination is more suggestive of **cytomegalovirus (CMV)** infection or **rubella**, which can cause petechial rash (blueberry muffin baby) and profound sensorineural deafness.
- *Toxoplasma gondii* does not typically cause a petechial rash as a primary symptom.
*Patent ductus arteriosus, cataracts, deafness*
- This constellation of symptoms is highly characteristic of **congenital rubella syndrome**.
- **Cardiac defects** (like patent ductus arteriosus), **ocular abnormalities** (cataracts), and **sensorineural deafness** are classical signs of rubella.
*Temporal encephalitis, vesicular lesions*
- **Temporal encephalitis** with vesicular lesions, particularly in a neonatal context, is a classic presentation of **congenital herpes simplex virus (HSV) infection**.
- *Toxoplasma gondii* can cause encephalitis, but not typically with vesicular lesions or a primary predilection for the temporal lobe in this specific clinical presentation.
Question 64: A 31-year-old man comes to the physician because of severe muscle pain and fever for 4 days. He likes to go hunting and consumed bear meat 1 month ago. Examination shows periorbital edema and generalized muscle tenderness. His leukocyte count is 12,000/mm3 with 19% eosinophils. The release of major basic protein in response to this patient’s infection is most likely a result of which of the following?
A. Increased expression of MHC class II molecules
B. Interaction between Th1 cells and macrophages
C. Antibody-dependent cell-mediated cytotoxicity (Correct Answer)
D. Increased expression of MHC class I molecules
E. Immune complex-dependent complement activation
Explanation: ***Antibody-dependent cell-mediated cytotoxicity***
- The patient's symptoms (fever, muscle pain, periorbital edema, eosinophilia) after consuming undercooked bear meat are highly suggestive of **trichinellosis**, a parasitic infection.
- **Eosinophils** are crucial in the immune response against parasites. They release cytotoxic substances like **major basic protein** through antibody-dependent cell-mediated cytotoxicity (ADCC), where antibodies (IgE or IgG) bind to the parasite, and eosinophils then bind to the Fc region of these antibodies to mediate parasite killing.
*Increased expression of MHC class II molecules*
- **MHC class II molecules** are primarily expressed on antigen-presenting cells (APCs) and are involved in presenting extracellular antigens to **CD4+ T cells**, initiating a helper T cell response.
- While important for activating the immune system, increased MHC class II expression doesn't directly explain the release of major basic protein by eosinophils in response to parasitic infection.
*Interaction between Th1 cells and macrophages*
- **Th1 cells** primarily activate **macrophages** to kill intracellular pathogens and are involved in cell-mediated immunity.
- This pathway is less prominent in directly killing large extracellular parasites like *Trichinella*, where eosinophil-mediated ADCC is key.
*Increased expression of MHC class I molecules*
- **MHC class I molecules** are expressed on almost all nucleated cells and present endogenous antigens to **CD8+ cytotoxic T cells**, primarily targeting intracellular viral infections and tumor cells.
- This mechanism is not directly involved in the eosinophil effector function against extracellular parasitic infections.
*Immune complex-dependent complement activation*
- **Immune complexes** (antigen-antibody complexes) can activate the complement system, leading to immune complex-mediated tissue damage or pathogen clearance.
- While complement can be involved in parasitic infections, it does not directly lead to the release of **major basic protein** by eosinophils, which is a specific cytotoxic mechanism.
Question 65: A 17-year-old Latin American woman with no significant past medical history or family history presents to her pediatrician with concerns about several long-standing skin lesions. She notes that she has had a light-colored rash on her chest and abdomen that has been present for the last 2 years. The blood pressure is 111/81 mm Hg, pulse is 82/min, respiratory rate is 16/min, and temperature is 37.3°C (99.1°F). Physical examination reveals numerous hypopigmented macules over her chest and abdomen. No lesions are seen on her palms or soles. When questioned, she states that these lesions do not tan like the rest of her skin when exposed to the sun. The remainder of her review of systems is negative. What is the most likely cause of these lesions?
A. Cutaneous T cell lymphoma
B. Post-viral immunologic reaction
C. Malassezia yeast (Correct Answer)
D. Treponema pallidum infection
E. TYR gene dysfunction in melanocytes
Explanation: ***Malassezia yeast***
- The presence of **long-standing hypopigmented macules** on the trunk that **do not tan with sun exposure** is highly characteristic of **tinea versicolor**, caused by *Malassezia* yeast.
- *Malassezia* produces **azelaic acid**, which inhibits melanin synthesis in melanocytes, leading to the characteristic hypopigmentation.
*Cutaneous T cell lymphoma*
- This typically presents as **erythematous patches or plaques** (mycosis fungoides) and would not primarily cause uniform hypopigmented macules that are exacerbated by sun exposure in this manner.
- While hypopigmented mycosis fungoides exists, it is rare and usually associated with other skin and systemic symptoms not described here.
*Post-viral immunologic reaction*
- A post-viral reaction might cause a rash, but it is unlikely to result in **chronic, localized hypopigmented macules** that specifically fail to tan.
- Such reactions are usually more generalized, self-limiting, or present with other characteristic features like pityriasis rosea.
*Treponema pallidum infection*
- **Syphilis** can cause a wide variety of skin manifestations, but hypopigmented macules on the trunk are not a typical presentation, especially without other signs of primary or secondary syphilis, and lesions would also appear on palms and soles.
- **Hyperpigmented macules** (syphilitic leukoderma) can rarely occur, but typically appear on the neck ("collar of Venus").
*TYR gene dysfunction in melanocytes*
- **TYR gene dysfunction** refers to mutations affecting **tyrosinase**, an enzyme crucial for melanin production. This is the underlying cause for **oculocutaneous albinism**, a condition characterized by widespread *congenital* hypopigmentation or amelanosis affecting skin, hair, and eyes.
- This patient's rash is described as "light-colored," "present for 2 years," and a late-onset issue, not a generalized congenital lack of pigmentation, making albinism unlikely.
Question 66: An 18-year-old man presents to the office, complaining of an itchy patch on his torso that appeared one week ago. The patient is on the college wrestling team and is concerned he will not be able to compete if it gets infected. He has no significant medical history, and his vital signs are within normal limits. On examination, there is an erythematous, scaly plaque with central clearing at approximately the level of rib 6 on the left side of his torso. What diagnostic test would be most appropriate at this time?
A. Eaton agar
B. Wood’s lamp examination
C. Thayer-Martin agar
D. Sabouraud agar
E. KOH preparation (Correct Answer)
Explanation: ***KOH preparation***
- A **KOH (potassium hydroxide) preparation** is the most appropriate initial diagnostic test for suspected **dermatophytosis** (ringworm), a common fungal infection often seen in wrestlers due to skin-to-skin contact.
- The KOH dissolves keratin and cellular debris, allowing for easier visualization of **fungal hyphae** and **spores** under a microscope, confirming the diagnosis.
*Eaton agar*
- **Eaton agar** is a specialized culture medium used for isolating and growing **Mycoplasma pneumoniae**, a bacterium that causes respiratory infections.
- It is not used for diagnosing fungal skin infections.
*Wood’s lamp examination*
- A **Wood's lamp examination** uses ultraviolet light to detect certain dermatophytes (like *Microsporum canis*), which may fluoresce
- However, many common dermatophytes, such as *Trichophyton rubrum*, do not fluoresce, making KOH preparation a more universally effective initial diagnostic tool.
*Thayer-Martin agar*
- **Thayer-Martin agar** is a selective culture medium primarily used for isolating and growing **Neisseria gonorrhoeae** and **Neisseria meningitidis**, bacteria responsible for sexually transmitted infections and meningitis, respectively.
- It is not indicated for diagnosing fungal skin infections.
*Sabouraud agar*
- **Sabouraud agar** is a recognized culture medium specifically designed for the isolation and identification of **fungi**, including dermatophytes.
- While useful for confirmation and species identification, a **KOH preparation** is a quicker and more immediate diagnostic test to confirm the presence of fungal elements in the clinic.
Question 67: A 45-year-old man is transferred to the intensive care unit from the emergency department for acute respiratory failure. He was rushed to the hospital after developing progressive respiratory distress over the last 24 hours. His medical history is significant for long-standing severe persistent asthma, hypertension, and several bouts of community and hospital-acquired pneumonia. His medications include amlodipine, lisinopril, inhaled fluticasone, salmeterol, and oral prednisone. He is a lifelong non-smoker and drinks alcohol occasionally on the weekends. He works as a sales executive and went to Hawaii a month ago. In the emergency department, he was started on broad-spectrum antibiotics and bronchodilators. His respiratory failure progressively worsens, and on day 2 of admission, he requires mechanical ventilator support. Chest X-ray shows multiple nodules bilaterally in the lower lobes. Flexible bronchoscopy is performed and the bronchoalveolar lavage sample from the medial segment of the right lower lobe shows neutrophils, and the fungal preparation shows Aspergillus fumigatus. A video-assisted thoracoscopy is performed and biopsy from the right lower lobe is taken which shows plugging of the terminal bronchioles with mucus, inflammatory cells, and fungal vascular invasion. Which of the following is the most likely mechanism responsible for the biopsy findings?
A. The production of a superantigen by Aspergillus fumigatus
B. Suppression of the innate immune system by Aspergillus fumigatus
C. Aspergillus fumigatus suppresses the production of IgA
D. Aspergillus fumigatus suppresses the production of IgM
E. Defects in the immune response (Correct Answer)
Explanation: ***Defects in the immune response***
- The patient's history of **long-standing severe persistent asthma** and **oral prednisone** use indicates an underlying altered immune status, making him susceptible to invasive fungal infections.
- The biopsy demonstrating **fungal vascular invasion** and the identification of *Aspergillus fumigatus* in a patient with immune compromise is characteristic of **invasive aspergillosis**.
*The production of a superantigen by *Aspergillus fumigatus***
- While some microorganisms produce superantigens, this mechanism is primarily associated with **bacterial toxins** (e.g., *Staphylococcus aureus*, *Streptococcus pyogenes*) causing widespread immune activation.
- **Invasive fungal infections** like aspergillosis are not typically characterized by superantigen production.
*Suppression of the innate immune system by *Aspergillus fumigatus***
- *Aspergillus fumigatus* itself does not directly suppress the innate immune system in a way that leads to invasive disease in an otherwise healthy individual.
- The host's **pre-existing immunosuppression** (e.g., from corticosteroids, chronic disease) is the primary factor allowing for fungal proliferation and invasion.
*Aspergillus fumigatus suppresses the production of IgA*
- **IgA** is primarily involved in mucosal immunity, and its suppression is not the main mechanism enabling **invasive aspergillosis**.
- No evidence suggests *Aspergillus* directly suppresses IgA production to facilitate vascular invasion.
*Aspergillus fumigatus suppresses the production of IgM*
- **IgM** is an early antibody in the humoral immune response, important for fighting acute infections.
- Suppression of IgM by *Aspergillus fumigatus* is not a recognized mechanism for the development of **invasive fungal disease**.
Question 68: A 27-year-old man presents to the emergency room with persistent fever, nausea, and vomiting for the past 3 days. While waiting to be seen, he quickly becomes disoriented and agitated. Upon examination, he has visible signs of difficulty breathing with copious oral secretions and generalized muscle twitching. The patient’s temperature is 104°F (40°C), blood pressure is 90/64 mmHg, pulse is 88/min, and respirations are 18/min with an oxygen saturation of 90% on room air. When the nurse tries to place a nasal cannula, the patient becomes fearful and combative. The patient is sedated and placed on mechanical ventilation. Which of the following is a risk factor for the patient’s most likely diagnosis?
A. Contaminated beef
B. Epiglottic cyst
C. Influenza vaccination
D. Spelunking (Correct Answer)
E. Mosquito bite
Explanation: ***Spelunking***
- This patient's symptoms (fever, disorientation, agitation, difficulty breathing with oral secretions, muscle twitching, and **hydrophobia**) are highly suggestive of **rabies**. Exposure to bats in caves (**spelunking**) is a common source of rabies infection.
- **Rabies** is a viral zoonotic disease that causes progressive and fatal encephalitis. The characteristic neurological symptoms, including hydrophobia (fear response to airflow/water), and rapid progression are pathognomonic for rabies.
*Contaminated beef*
- **Contaminated beef** is associated with foodborne illnesses like E. coli O157:H7 or prion diseases (variant Creutzfeldt-Jakob disease).
- These conditions do not typically present with the acute, severe neurological symptoms, hydrophobia, and respiratory distress seen in this patient.
*Epiglottic cyst*
- An **epiglottic cyst** can cause airway obstruction, leading to difficulty breathing, stridor, and dysphagia.
- However, it does not explain the systemic symptoms like fever, disorientation, agitation, muscle twitching, or the hydrophobia when attempting nasal cannula placement, which are classic signs of rabies encephalitis.
*Influenza vaccination*
- **Influenza vaccination** is generally safe; side effects are usually mild and include soreness at the injection site, low-grade fever, and muscle aches.
- It is not a risk factor for a severe, rapidly progressive neurological illness like rabies.
*Mosquito bite*
- **Mosquito bites** can transmit various arboviruses causing encephalitis (e.g., West Nile virus, Eastern equine encephalitis).
- While arboviruses can cause encephalitis with fever and neurological symptoms, the prominent **hydrophobia** and copious oral secretions are pathognomonic for rabies rather than typical arboviral encephalitides.
