Which of the following is NOT one of the four syndromes of severe arbovirus infection?

• A. Fever and myalgia
• B. Arthritis and rash
• C. Encephalitis
• D. Respiratory failure

Answer: (D)

Arbovirus infections can present in several distinct severe patterns that involve different body systems. The four classic severe syndromes are a systemic febrile illness with prominent myalgias, a polyarthralgia with a rash, encephalitis from nervous system involvement, and a hemorrhagic fever with shock. Respiratory failure is not a defined arbovirus syndrome; it may occur as a serious complication but not as one of the characteristic syndromes used to categorize severe arbovirus disease. Therefore, respiratory failure is the best answer because it does not fit the established syndromic patterns. The other options align with recognized severe presentations: fever with myalgia represents a systemic febrile syndrome; arthritis with rash reflects joint and skin involvement seen in certain arboviruses; encephalitis denotes CNS infection by these viruses.