Arbovirus

1. An outbreak of dengue hemorrhagic fever (DHF) recently occurred in two Central American countries. Regarding dengue and DHF, which one of the following is the most accurate?

• (A) Humans are dead-end hosts for dengue virus.
• (B) DHF occurs primarily in individuals who are deficient in the late-acting complement components.
• (C) Dengue virus is transmitted by Aedes mosquitoes, and monkeys are an important natural reservoir.
• (D) The vaccine containing live, attenuated dengue virus is recommended for those living or traveling in endemic areas.
• (E) DHF occurs more often in people infected for the first time than when they are reinfected because antibody protects against reinfection.

2. Yellow fever still exists in many tropical areas of the globe. Which one of the following is the best reason yellow fever still exists?

• (A) Sewage disposal is inadequate in many areas.
• (B) Both humans and monkeys are reservoirs for yellow fever virus.
• (C) The virus has mutated, so the existing vaccine is no longer effective.
• (D) The vaccine has been withdrawn because it was found to have unacceptable side effects.
• (E) The people in developing countries cannot afford to take amantadine when they enter endemic areas.

3. Regarding West Nile virus (WNV), which one of the following is the most accurate?

• (A) Rodents are the main reservoir for WNV.
• (B) WNV does not cause disease in the United States.
• (C) WNV is transmitted primarily by Ixodes ticks.
• (D) Most infections are asymptomatic, but the elderly are at risk for encephalitis.
• (E) The live, attenuated vaccine should be administered to elderly adults in endemic areas.

4. An outbreak of febrile disease involving severe joint pain and an erythematous macular rash has occurred on several Caribbean islands. Infection with chikungunya virus is suspected. Which one of the following is correct regarding this virus?

• (A) Its genome is composed of double-stranded DNA.
• (B) It is transmitted by Aedes mosquitoes.
• (C) Wild birds are the most important reservoir.
• (D) Laboratory diagnosis involves electron microscopy to observe the very long filamentous shape of the virus.
• (E) The killed vaccine should be administered to travelers to endemic regions.