Dengue and chikungunya

What are dengue and chikungunya?

In plain words: both illnesses are caused by viruses that live in mosquitoes as well as in people. A mosquito picks up the virus from an infected person and can pass it on only after the virus has multiplied inside it for several days and reached its salivary glands, so not at its very next bite (beyond the NCERT text; the WHO chikungunya fact sheet describes this for chikungunya, facts in our words). Cutting down mosquitoes cuts down both diseases.

The 2026–27 NCERT book has no section on these diseases; it only names them, in the line above. The NEET (UG) 2026 syllabus lists dengue and chikungunya in Unit 8. Everything below except the mosquito control of NCERT page 134 is beyond the NCERT text, from MedlinePlus (US National Library of Medicine, public domain), and from Wikipedia and the WHO chikungunya fact sheet (facts in our words).

Dengue

• Cause: dengue is a viral infection, and MedlinePlus notes that it “can be caused by four related viruses”. These are the four serotypes of the dengue virus, an RNA virus of the family Flaviviridae (Wikipedia, “Dengue virus”). See viruses in NCERT Class 11 Biology, Chapter 2.
• Spread: through the bite of an infected mosquito, chiefly Aedes aegypti (Wikipedia, “Dengue virus”). MedlinePlus adds: “It does not spread directly from person to person.” It can pass to the baby during pregnancy and, rarely, through blood transfusion, organ transplant or a needle-stick injury (MedlinePlus).
• Who falls ill: about 1 in 4 people infected with dengue get sick. For them it can be mild or severe (MedlinePlus).
• Symptoms: a high fever, nausea and vomiting, a rash, and aches and pains: pain behind the eyes, and in the muscles, joints or bones. Symptoms usually go on for two to seven days. Another name for dengue is break-bone fever (MedlinePlus).
• Severe dengue: about 1 in 20 of those who fall ill go on to severe dengue, which can lead to shock, internal bleeding and even death. It is more likely in people who have had dengue before, in pregnant women and in infants (MedlinePlus).
• Diagnosis and treatment: a blood test can show whether a person has been infected. MedlinePlus says: “There is no specific medicine to treat dengue.” Most people recover in about a week, and people with severe dengue often need hospital care. The warning signs of severe dengue, such as severe belly pain, repeated vomiting and bleeding from the nose or gums, typically appear 24–48 hours after the fever ends (beyond the NCERT text; MedlinePlus).

Chikungunya

• Cause and spread: the chikungunya virus is carried by the same kinds of mosquitoes as dengue (MedlinePlus). The virus belongs to the genus Alphavirus, and it is carried mainly by Aedes aegypti and Aedes albopictus. These mosquitoes are day-biters: most of their bites come in the daytime (WHO, Chikungunya fact sheet, 14 April 2025, facts in our words).
• Symptoms: they usually start 3–7 days after the bite. The most common are fever and joint pain; others include headache, muscle pain, joint swelling and rash (MedlinePlus).
• Course: most people recover within a week, but in some people the joint pain goes on for months (MedlinePlus).

Dengue and chikungunya compared

• Virus: dengue, the dengue virus with four serotypes (family Flaviviridae); chikungunya, the chikungunya virus (genus Alphavirus).
• Vector: dengue, Aedes mosquitoes, chiefly Aedes aegypti; chikungunya, the same Aedes mosquitoes (A. aegypti, A. albopictus).
• Main symptoms: dengue, high fever, rash, and pain behind the eyes and in the muscles, joints and bones; chikungunya, fever and joint pain.
• Important complications: dengue, severe dengue with shock and internal bleeding; chikungunya, joint pain that in some people lasts for months. Lasting joint pain is a long-term complication, not an emergency like the shock of severe dengue (our reasoning).

(MedlinePlus; Wikipedia, “Dengue virus” and “Chikungunya”.)

Prevention: controlling the mosquito

NCERT’s measures against vector-borne diseases (page 134) apply directly to the Aedes mosquito, which NCERT Class 11 Biology, Chapter 4, lists among the insect vectors:

• avoid stagnation of water in and around homes, and clean household coolers regularly;
• use mosquito nets, and fit doors and windows with wire mesh;
• introduce fishes such as Gambusia, which feed on mosquito larvae, into ponds;
• spray insecticides in ditches, drainage areas and swamps.

Beyond the NCERT text: the WHO chikungunya fact sheet adds that communities can empty and scrub water-holding containers once a week, get rid of rubbish and back local mosquito-control work (facts in our words), and MedlinePlus adds insect repellent and clothes that cover the arms, legs and feet. The mosquitofish (Gambusia affinis) has harmed native water life where people brought it into waters outside its home range, for example by eating or out-competing small native fish (Wikipedia, “Mosquitofish”, facts in our words).

Because these mosquitoes bite mainly by day, daytime protection matters, including nets for people who sleep during the day (WHO chikungunya fact sheet, facts in our words). “Mainly” means some bites also come at other times (our reasoning).

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Quick revision summary

• NCERT names dengue and chikungunya only as diseases spread by Aedes mosquitoes, whose spread in India makes mosquito control more important (page 134). The details below are beyond the NCERT text.
• Dengue: four related viruses (serotypes; family Flaviviridae); usually mosquito-borne, not spread by casual contact; about 1 in 4 infected fall sick; high fever, rash, pain behind the eyes and in muscles, joints and bones, for 2–7 days; about 1 in 20 of the sick get severe dengue (shock, internal bleeding); blood test; no specific medicine; warning signs typically 24–48 hours after the fever ends.
• Chikungunya: an alphavirus (genus Alphavirus); the same day-biting mosquitoes; fever and joint pain, starting 3–7 days after the bite; in some people joint pain lasts months.
• Prevention (NCERT page 134): no stagnant water, clean coolers, nets, wire mesh, larva-eating fish, insecticides; beyond the NCERT text, daytime bite protection.

Questions students ask

Are dengue and chikungunya in the NEET (UG) 2026 syllabus?

Yes, dengue and chikungunya are in the NEET (UG) 2026 syllabus: Unit 8, Biology and Human Welfare, lists “parasites causing human diseases (Malaria, Filariasis, Ascariasis. Typhoid, Pneumonia, common cold, amoebiasis, ring worm, dengue, chikungunya)”. The 2026–27 NCERT reprint has no section on either disease; it names them once, on page 134, as vector-borne diseases whose recent widespread incidence in many parts of India makes mosquito control more important.

Which is more dangerous, dengue or chikungunya?

Beyond the NCERT text, dengue carries the greater risk to life (our reading of two sources): MedlinePlus (US National Library of Medicine) describes severe dengue, which develops in a small share of those who fall sick, as a serious form that can be fatal, while CDC (2026) states that “death from chikungunya is rare”. CDC adds that chikungunya’s joint pain “can be severe and disabling”, and that people with medical conditions such as high blood pressure, diabetes or heart disease, adults aged 65 years and older, and newborns infected around the time of birth are at risk of more severe illness.

What is the difference between dengue and malaria?

Dengue and malaria differ in their cause and in their vector: NCERT names Plasmodium, a protozoan carried by the female Anopheles, as the cause of malaria (page 131), while dengue is, beyond the NCERT text, a viral infection (MedlinePlus), spread mainly by infected Aedes mosquitoes (NCERT page 134; CDC, 2025). Also beyond the NCERT text, the vectors feed at different times, Aedes mostly by day (WHO, 2025) and Anopheles especially in the late evening and at night (CDC, 2024). NCERT describes malaria’s chill and high fever recurring every three to four days (page 131), while dengue’s high fever comes with a rash and pain behind the eyes (MedlinePlus, beyond the NCERT text).

Why is chikungunya called chikungunya?

Beyond the NCERT text, chikungunya is named after a word of the Makonde people of Tanzania that meant “that which bends up”: Gudo and colleagues (PLoS Neglected Tropical Diseases, 2016, CC BY) write that the authors of the first reports, on the epidemic of 1952–1953 in what was then Tanganyika, took up the local Makonde name for the disease. The World Health Organization (2025) explains the picture behind the word: the bent, twisted way patients hold themselves when the infection makes their joints badly painful.

Practice questions

Try each question first, then open the answer to check your working.

1. Q1. Which mosquito spreads dengue and chikungunya, according to NCERT?

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   Aedes mosquitoes (NCERT page 134).

2. Q2. What are the most common symptoms of chikungunya?

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   Fever and joint pain (beyond the NCERT text; MedlinePlus).

3. Q3. Name two measures from NCERT that reduce mosquito breeding.

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   Any two of: avoiding stagnant water around homes, cleaning household coolers regularly, introducing larva-eating fishes such as Gambusia into ponds, and spraying insecticides in ditches, drainage areas and swamps (NCERT page 134).