Epstein-Barr virusDownloads

A 20-year-old man presents to the emergency department with complaints of severe malaise, fevers, and sore throat for the past 7 days. He also has had episodes of nausea and vomiting during this period. He does not smoke or drink alcohol. There is no family history of liver disease. His blood pressure is 130/80 mm Hg, temperature is 38.3℃ (100.9℉), pulse is 102/min, and respiratory rate is 20/min. On physical examination, he appears ill with bilateral cervical lymphadenopathy. His tonsils are erythematous and enlarged. There is no jaundice and he is mildly dehydrated. Abdominal examination demonstrates splenomegaly. The laboratory findings are shown below: Hemoglobin 15 g/dL Platelet count 95,000/mm³ Leukocytes 13,500/mm³ Neutrophils 50% Atypical lymphocytes 34% AST 232 U/L ALT 312 U/L ALP 120 U/L GGT 35 U/L Total bilirubin 1.2 mg/dL Direct bilirubin 0.2 mg/dL PT 12 seconds The serologic test for hepatitis A, B, and C, CMV, and leptospirosis are negative. Serology for both serum IgM and IgG antibodies for EBV capsid antigen are positive, but the heterophile antibody test is negative. What is the most likely reason for the negative heterophile test?

A 17-year-old boy comes to the physician because of body aches and sore throat for 1 week. He has no history of serious illness and takes no medications. He lives with his parents; they recently adopted a cat from an animal shelter. He is sexually active with one female partner, and they use condoms consistently. His temperature is 38.7°C (101.7°F), pulse is 99/min, and blood pressure is 110/72 mm Hg. Examination shows bilateral posterior cervical lymphadenopathy. The pharynx is red and swollen. Laboratory studies show: Hemoglobin 15 g/dL Leukocyte count 11,500/mm3 Segmented neutrophils 48% Band forms 2% Basophils 0.5% Eosinophils 1% Lymphocytes 45% Monocytes 3.5% When the patient's serum is added to a sample of horse erythrocytes, the cells aggregate together. Which of the following is the most likely causal pathogen?