Consider the following statements: 1. In tropical regions, Zika virus disease is transmitted by the same mosquito that transmits dengue. 2. Sexual transmission of Zika virus disease is possible. Which of the statements given above is/are correct?
Contents19
- A1 only
- B2 only
- CBoth 1 and 2
- DNeither 1 nor 2
Show answer
Answer: (C) Both 1 and 2
Both statements are correct.
Statement 1 is correct:
Zika virus is primarily transmitted to humans through the bite of an infected mosquito from the Aedes genus, mainly Aedes aegypti in tropical regions.
This is the SAME mosquito species that transmits dengue, chikungunya, and yellow fever.
This is an important connection to remember — Aedes aegypti is the common vector for multiple viral diseases.
The mosquito is identifiable by white markings on its legs and breeds in stagnant fresh water (flower pots, tyres, water containers, etc.).
Statement 2 is correct:
Although Zika is primarily a mosquito-borne disease, sexual transmission of Zika virus has been confirmed.
The virus can be present in semen for weeks after infection, even after symptoms have resolved.
This was a significant finding during the 2015-16 Zika outbreak because it meant that the virus could spread even in areas without the Aedes mosquito.
Other transmission routes include mother-to-foetus during pregnancy (which can cause microcephaly — a birth defect where the baby's head is abnormally small) and through blood transfusion.
The WHO confirmed India's first three cases of Zika virus in 2017.
So both statements 1 and 2 are correct.
Zika virus shares the same Aedes aegypti mosquito vector with dengue, chikungunya, and yellow fever, making vector control strategies similar across these diseases.
The 2015-16 global Zika outbreak revealed sexual transmission as a key route, allowing spread even in areas without Aedes mosquitoes, and WHO confirmed India's first cases in 2017.
UPSC is testing whether students understand both the primary transmission route and the alternative non-vector transmission methods that make Zika epidemiologically distinct.
Zika Virus Disease
Science And Technology Zika virus disease Sexual transmission
Zika Virus Disease: Transmission, Symptoms & Global Impact
Aedes aegypti mosquito transmits Zika, dengue, chikungunya, and yellow fever
Sexual transmission confirmed - virus persists in semen for weeks
Causes microcephaly in babies when pregnant women infected
India reported first 3 cases in 2017
What is Zika
Zika is a viral disease first identified in Uganda's Zika Forest in 1947. It became a global health emergency in 2015-16 due to its link with severe birth defects.
Zika Transmission Routes
Route | Details | Risk Level | Key Point |
|---|---|---|---|
Mosquito bite | Aedes aegypti (primary vector) | High | Same mosquito as dengue |
Sexual contact | Virus in semen for weeks | Moderate | Spreads without mosquitoes |
Mother to baby | During pregnancy | High | Causes microcephaly |
Blood transfusion | Through infected blood | Low | Rare but documented |
Clinical Features
Mild symptoms in most adults: fever, rash, joint pain, red eyes
80% of infections are asymptomatic
Microcephaly in newborns is the most serious complication
Guillain-Barré syndrome (muscle weakness) linked to Zika infection
Aedes Aegypti Identification
Source: Liv Hospital — How to Identify Aedes Aegypti Dengue Mosquitoes · int.livhospital.com
Trap: Don't confuse with Anopheles (malaria vector) or Culex (Japanese encephalitis vector)
Trap: Sexual transmission makes Zika unique among mosquito-borne diseases - remember this distinction
Trap: Zika causes microcephaly, not macrocephaly (enlarged head)
Trap: Same vector as dengue but different from malaria mosquito
Aedes Aegypti Mosquito
Science And Technology mosquito dengue
Aedes Aegypti: The Multi-Disease Vector
Transmits 4 major viral diseases: Zika, dengue, chikungunya, yellow fever
Breeds in clean stagnant water around homes
White markings on legs distinguish it from other mosquitoes
Day-biting mosquito, most active during dawn and dusk
Why It's Dangerous
Aedes aegypti is called the 'urban mosquito' because it thrives in human settlements. Unlike malaria mosquitoes that bite at night, Aedes is a day-biter that lives close to humans.
Diseases Transmitted by Aedes Aegypti
Disease | Virus Family | Key Symptom | Serious Complication |
|---|---|---|---|
Dengue | Flavivirus | High fever, bleeding | Dengue shock syndrome |
Zika | Flavivirus | Mild fever, rash | Microcephaly in babies |
Chikungunya | Alphavirus | Severe joint pain | Chronic arthritis |
Yellow Fever | Flavivirus | Jaundice | Liver failure, death |
Breeding & Control
Breeds in artificial containers: flower pots, tyres, water tanks, coolers
Requires only small amounts of clean water to lay eggs
Dry container strategy - remove stagnant water sources
Biological control using Wolbachia bacteria being tested globally
Mosquito Vector Classification
# Disease Vectors
## Aedes aegypti
- Zika
- Dengue
- Chikungunya
- Yellow Fever
## Anopheles
- Malaria
- Lymphatic Filariasis
## Culex
- Japanese Encephalitis
- West Nile VirusTrap: Aedes transmits viral diseases, Anopheles transmits parasitic malaria
Trap: Aedes breeds in clean water, not dirty water like some other mosquitoes
Trap: Day-biting vs night-biting (Anopheles) - remember the timing difference
Trap: All four Aedes-borne diseases are viral, not bacterial or parasitic
Vector-Borne Diseases in India
Science And Technology
Vector-Borne Diseases in India: Major Threats & Control Programs
NVBDCP (National Vector Borne Disease Control Programme) is the nodal program
India reports Zika cases since 2017, dengue cases in millions annually
Malaria still major killer despite 70% reduction since 2000
Japanese Encephalitis endemic in 179 districts across 24 states
India's Challenge
India bears 60% of global malaria burden outside Africa and faces multiple vector-borne diseases simultaneously. Climate change and urbanization are expanding vector habitats.
Major Vector-Borne Diseases in India
Disease | Vector | Endemic States | Annual Cases | Key Challenge |
|---|---|---|---|---|
Malaria | Anopheles | Odisha, Jharkhand, Chhattisgarh | ~5 lakh | Rural tribal areas |
Dengue | Aedes aegypti | Delhi, Punjab, West Bengal | ~1-2 lakh | Urban outbreaks |
Chikungunya | Aedes aegypti | Karnataka, Maharashtra, Kerala | ~50,000 | Seasonal epidemics |
Japanese Encephalitis | Culex | Assam, UP, Bihar, West Bengal | ~5,000 | Children mortality |
Zika | Aedes aegypti | Rajasthan, MP, Gujarat | <100 | Pregnancy complications |
Government Initiatives
National Framework for Malaria Elimination (2016-30) targets zero indigenous malaria by 2030
Intensified Mission Indradhanush includes Japanese Encephalitis vaccination
Integrated Disease Surveillance Programme for early outbreak detection
Urban Malaria Scheme focuses on 132 endemic urban areas
Disease Distribution Map
India map showing state-wise distribution of vector-borne diseases with different colors for malaria, dengue, Japanese encephalitis endemic zones
Eastern and central India bear the highest malaria burden, while dengue affects urban centers nationwide
Trap: NVBDCP controls vector-borne diseases, not NRHM or other health programs
Trap: Malaria elimination by 2030, not eradication - elimination means zero indigenous cases
Trap: Japan Encephalitis vaccine included in routine immunization, Zika vaccine still under trial
Trap: India's first Zika cases in 2017 in Ahmedabad, Gujarat
Viral Disease Transmission Modes
Science And Technology transmitted
Viral Disease Transmission: Vector-Borne vs Direct Routes
Vector-borne transmission requires intermediate host (mosquito, tick, fly)
Direct transmission includes airborne, contact, sexual, and vertical routes
Zika is unique - primarily vector-borne but also sexually transmitted
Understanding transmission guides prevention strategies
Why Transmission Matters
Understanding how viruses spread determines prevention strategies. Vector-borne diseases need vector control, while sexually transmitted diseases need behavioral interventions.
Viral Disease Transmission Classification
Transmission Type | Examples | Prevention Strategy | UPSC Favorites |
|---|---|---|---|
Vector-borne | Dengue, Zika, Yellow Fever, JE | Vector control, eliminate breeding sites | Aedes-borne diseases |
Airborne | Influenza, COVID-19, Measles | Masks, ventilation, vaccination | Respiratory viruses |
Sexual | HIV, Hepatitis B, Zika | Safe practices, barrier methods | Zika dual transmission |
Vertical | Zika, HIV, Hepatitis B | Antenatal screening, treatment | Mother-to-child |
Contact | Ebola, Marburg, Monkeypox | Isolation, PPE, hygiene | Hemorrhagic fevers |
Vector-Borne Disease Cycle
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**Infected Human**
Person with viremia (virus in blood)`"]
s2["`**Mosquito Bite**
Aedes aegypti feeds on infected blood`"]
s3["`**Viral Replication**
Virus multiplies in mosquito gut and salivary glands`"]
s4["`**Infectious Mosquito**
Mosquito becomes capable of transmission`"]
s5["`**New Human Host**
Mosquito bites healthy person, transmits virus`"]
s1 --> s2
s2 --> s3
s3 --> s4
s4 --> s5Trap: Zika has both vector and sexual transmission - don't choose only one mode
Trap: Japanese Encephalitis is vector-borne only, no sexual transmission
Trap: Malaria is parasitic (not viral) but also vector-borne through Anopheles
Trap: Vertical transmission means mother-to-child, not person-to-person contact