Zika virus is transmitted by:

Explanation

## Correct Answer: A. Aedes aegypti Zika virus is a flavivirus transmitted exclusively by **Aedes aegypti** mosquitoes, the same vector responsible for dengue and chikungunya in India. This urban-adapted, anthropophilic mosquito breeds in stagnant water around human habitations (flower pots, coolers, discarded containers) and feeds preferentially on humans during dawn and dusk. The virus replicates in the mosquito's midgut and salivary glands, achieving competence within 10–14 days post-infection. Aedes aegypti is highly efficient at human-to-human transmission due to its aggressive biting behavior and close association with human settlements. In India, Zika virus was first detected in 2016 in Rajasthan and subsequently in other states, with Aedes aegypti confirmed as the primary vector. The virus causes a mild febrile illness but gained notoriety for its association with congenital Zika syndrome (microcephaly, CNS malformations) when acquired during pregnancy, particularly in the first trimester. Vector control targeting Aedes aegypti—through source reduction, insecticide spraying, and community education—remains the cornerstone of Zika prevention in endemic regions. ## Why the other options are wrong **B. Anopheles** — Anopheles mosquitoes are the vectors for malaria (Plasmodium) and Japanese encephalitis (JEV), not Zika. They breed in clean water bodies and have a different feeding behavior (nocturnal, outdoor resting). This is a classic NBE trap pairing a flavivirus with the wrong vector; students may confuse Zika with JEV, which is also a flavivirus but transmitted by Culex, not Anopheles. **C. Phlebotomus papatasii** — Phlebotomus papatasii is a sandfly vector for Pappataci fever (Phlebovirus) and leishmaniasis, not Zika. Sandflies are small, nocturnal insects with a different ecology and geographic distribution. This option exploits confusion between arthropod-borne viruses; students unfamiliar with vector taxonomy may incorrectly associate any arbovirus with any arthropod vector. **D. Culex** — Culex mosquitoes transmit Japanese encephalitis, West Nile virus, and lymphatic filariasis, not Zika. While Culex is a flavivirus vector, it is not involved in Zika transmission. The trap here is that both Zika and JEV are flaviviruses; students may incorrectly assume all flaviviruses share the same vector, conflating Culex (JEV vector) with Aedes (Zika vector). ## High-Yield Facts - **Aedes aegypti** is the sole vector for Zika virus; it is the same mosquito that transmits dengue and chikungunya in India. - Zika virus is a **flavivirus** (genus Flavivirus, family Flaviviridae); other flaviviruses (JEV, dengue, yellow fever) have different vectors. - **Congenital Zika syndrome** (microcephaly, CNS malformations) occurs when infection happens in the first trimester of pregnancy; vertical transmission is documented. - Aedes aegypti breeds in **stagnant water near human habitats** (flower pots, coolers, discarded containers); it is anthropophilic and bites during dawn and dusk. - **Extrinsic incubation period** in the mosquito is 10–14 days; viremia in humans lasts 3–14 days, during which they can infect feeding mosquitoes. - Zika was first detected in India in **2016 in Rajasthan**; subsequent cases confirmed the presence of Aedes aegypti-mediated transmission in Indian urban centers. ## Mnemonics **Aedes = Dengue, Chikungunya, Zika (DAZ)** Remember **Aedes aegypti** as the vector for three major arboviruses in India: **D**engue, **A**rbo (Zika), **Z**ika. All three are urban, daytime-biting, stagnant-water-breeding vectors. **Flavivirus Vector Pairing** **Aedes** → Dengue, Zika, Yellow Fever (urban); **Culex** → JEV, West Nile (rural); **Anopheles** → Malaria (not a flavivirus). Use this to distinguish flaviviruses by their vectors. ## NBE Trap NBE pairs Zika (a flavivirus) with Culex (which transmits JEV, another flavivirus) to trap students who assume all flaviviruses share the same vector. The key discriminator is that Zika is **Aedes-specific**, not Culex-transmitted. ## Clinical Pearl In Indian urban centers, Aedes aegypti control is critical during monsoon and post-monsoon seasons when stagnant water accumulates. Pregnant women in endemic areas (Rajasthan, parts of Tamil Nadu) should be counseled on mosquito avoidance and insecticide-treated nets to prevent congenital Zika syndrome, which carries high morbidity. _Reference: Jawetz, Melnick & Adelberg's Medical Microbiology (Ch. Arboviruses); Park's Textbook of Preventive and Social Medicine (Ch. Communicable Diseases)_