A photographer who recently returned from Africa presents to the emergency department with abdominal pain, hepatomegaly, and hemorrhagic manifestations. He died despite treatment, and an autopsy revealed intranuclear Torres bodies in the liver. Which of the following vaccines with which strain could have prevented it?

Explanation

## Correct Answer: C. 17D The clinical presentation—recent travel to Africa, hepatomegaly, hemorrhagic manifestations, and death despite treatment—combined with the pathognomonic **intranuclear Torres bodies** in hepatocytes at autopsy, is diagnostic of **yellow fever**. Torres bodies are eosinophilic, intranuclear inclusions pathognomonic for yellow fever virus (YFV), a flavivirus transmitted by *Aedes aegypti* mosquitoes in tropical Africa and South America. The **17D vaccine** is the only live attenuated yellow fever vaccine in current use globally and is the WHO-recommended vaccine for yellow fever prevention. It was developed by Max Theiler in 1937 through serial passage of the wild-type Asibi strain in chicken embryo tissue culture, producing a safe, immunogenic live attenuated strain. The 17D vaccine provides lifelong immunity with a single dose and is the standard of care for travelers to endemic regions. In India, yellow fever vaccination is mandatory for travelers returning from or traveling to endemic countries (parts of Africa, South America) and is available at authorized yellow fever vaccination centers. The other options represent vaccines against entirely different pathogens: Weigl's vaccine (typhus), Nakayama vaccine (Japanese encephalitis), and Jeryl Lynn (mumps)—none of which cause Torres bodies or the hemorrhagic hepatic syndrome described. ## Why the other options are wrong **A. Weigl's vaccine** — Weigl's vaccine is used against **Rickettsia prowazekii** (epidemic typhus), not yellow fever. While typhus can cause fever and hepatomegaly, it does not produce Torres bodies. This is a distractor that tests knowledge of vaccine-pathogen pairing; the clinical context (Africa, hemorrhagic hepatitis, Torres bodies) is specific to yellow fever. **B. Nakayama vaccine** — Nakayama is a live attenuated vaccine against **Japanese encephalitis virus**, endemic in Asia (including India), not Africa. JEV causes encephalitis and meningitis, not the hemorrhagic hepatic syndrome with Torres bodies. This trap exploits confusion between flaviviruses; both YFV and JEV are flaviviruses, but their epidemiology, pathology, and vaccines differ fundamentally. **D. Jeryl Lynn strain** — Jeryl Lynn is a live attenuated strain of **mumps virus**, used in the MMR vaccine. Mumps causes parotitis and meningitis, not hepatitis or hemorrhagic manifestations. This is a pure distractor testing whether students conflate vaccine strain names; the pathology (Torres bodies, hemorrhagic hepatitis) is entirely incompatible with mumps. ## High-Yield Facts - **Torres bodies** are intranuclear, eosinophilic inclusions pathognomonic for yellow fever virus infection in hepatocytes. - **17D vaccine** is a live attenuated yellow fever vaccine developed by serial passage in chicken embryo tissue; provides lifelong immunity with one dose. - Yellow fever is endemic in **tropical Africa and South America**; transmitted by *Aedes aegypti* mosquitoes; case fatality rate 15–50% in severe hemorrhagic form. - Yellow fever vaccination is **mandatory for travelers** to endemic regions in India; available only at authorized yellow fever vaccination centers (AYVC). - **Flavivirus** family includes yellow fever, dengue, Zika, and Japanese encephalitis; 17D is specific to YFV, not cross-protective against other flaviviruses. ## Mnemonics **TORRES = Yellow Fever Pathology** **T**ropical Africa/Americas, **O**intment-like (eosinophilic) intranuclear bodies, **R**iddled liver (hepatomegaly + necrosis), **R**ed hemorrhages (bleeding), **E**ndothelial damage, **S**evere mortality. Use when you see intranuclear inclusions + hepatitis + hemorrhage in a traveler. **17D = Yellow fever Vaccine** **1**7th passage, **D**eveloped by Theiler, **D**ose = one lifetime dose, **D**uration = lifelong immunity. Mnemonic: 17D is the gold standard live attenuated YFV vaccine. ## NBE Trap NBE pairs yellow fever with other tropical hemorrhagic fevers (dengue, Lassa) and tests whether students can identify the **pathognomonic Torres body** as the discriminating feature. The distractor vaccines (Weigl's, Nakayama, Jeryl Lynn) exploit confusion between vaccine strain names and flavivirus taxonomy, luring students who know these vaccines exist but haven't anchored them to specific pathogens.</trap> <parameter name="textbookRef">Jawetz, Melnick & Adelberg's Medical Microbiology (Yellow Fever & Flaviviruses); Harrison's Principles of Internal Medicine Ch. 189 (Yellow Fever); Park's Textbook of Preventive and Social Medicine (Immunization in India) ## Clinical Pearl In Indian clinical practice, any traveler returning from endemic African or South American regions with fever, hepatomegaly, and hemorrhagic manifestations should raise suspicion for yellow fever—a notifiable disease. The 17D vaccine is the only preventive measure; post-exposure prophylaxis does not exist, making pre-travel vaccination critical. Indian travelers to endemic countries must obtain vaccination from authorized centers and carry the International Certificate of Vaccination.