In this article
- Monsoon disease calendar — when each peaks
- Dengue — the most dangerous
- Chikungunya — joint pain that lingers
- Malaria — still endemic, often missed
- Leptospirosis — the flood-water disease
- Typhoid and waterborne illnesses
- Plain viral fever — when to relax, when to worry
- Which blood tests, when
- Prevention checklist
- Frequently asked questions
Monsoon disease calendar — when each peaks
| Month | Diseases to watch | Why |
|---|---|---|
| June | Leptospirosis, viral fevers, early dengue, typhoid | First rains; flooding; water contamination |
| July | Malaria, typhoid, Hepatitis A & E, gastroenteritis | Standing water, food contamination peaks |
| August | Dengue, malaria, chikungunya, leptospirosis | Stagnant water in containers; Aedes peaks |
| September | Dengue (peak), chikungunya, scrub typhus | Maximum vector breeding window |
| October | Dengue tail, chikungunya tail, asthma flare | Receding rains; AQI worsens |
Dengue — the most dangerous
Symptoms (Day-by-day)
- Days 1–3: High fever (39–40°C), severe headache, pain behind the eyes, severe muscle and joint pain ("break-bone fever"), nausea, vomiting, rash.
- Days 4–6 (critical phase): Fever drops — but this is the most dangerous window. Plasma leakage can start. Watch for warning signs.
- Days 7+ (recovery): Fluid reabsorption, fatigue, recovery rash, mood swings.
- Platelet count below 50,000/μL (or rapidly falling)
- Severe abdominal pain
- Persistent vomiting (more than 3 times in 1 hour)
- Bleeding gums, nosebleeds, blood in vomit or stool
- Restlessness, lethargy or confusion
- Cold, clammy hands; rapid weak pulse
- Reduced or no urine output for 6+ hours
Tests
- Days 1–5: Dengue NS1 antigen + CBC with platelet count
- Day 5+: Dengue IgM/IgG antibody + CBC daily
- Cost: ₹500–1,500 in private labs; free in government hospitals
Treatment
No specific antiviral. Treatment is supportive: paracetamol for fever (NEVER aspirin, ibuprofen or other NSAIDs — they worsen bleeding risk), oral fluids/ORS, hospitalisation for warning signs. Platelet transfusion is reserved for very specific criteria — most dengue patients with platelets above 20,000 do NOT need transfusion. Beware private hospitals over-prescribing platelets.
Chikungunya — joint pain that lingers
Tamil Nadu's 2026 surge has put chikungunya back on the public-health radar. Eight districts have issued public-safety advisories as of late May 2026.
How chikungunya differs from dengue
| Feature | Dengue | Chikungunya |
|---|---|---|
| Fever | Higher (39–40°C), shorter | Sudden, very high, 2–5 days |
| Joint pain | Generalised body pain | Severe joint pain, persists for weeks to months |
| Rash | Days 3–7, may itch | Days 2–5, often blotchy |
| Platelets | Often drop sharply | Rarely drop dangerously |
| Bleeding risk | Yes (warning signs) | Very rare |
| Long-term issues | Usually full recovery | Chronic arthritis in 20–30% (up to 1 year) |
Treatment
Supportive: paracetamol, rest, hydration, joint physiotherapy if pain lingers. Most patients recover from fever in 5–7 days but joint pain can persist for weeks or months. Anti-inflammatory drugs (NSAIDs) can help after day 7 — only on doctor's advice and only after dengue has been ruled out.
Malaria — still endemic, often missed
India recorded over 1.7 lakh malaria cases in 2024. Often missed in cities because doctors think first of dengue. Plasmodium vivax causes most cases; P. falciparum is more dangerous.
Symptoms
- Cyclic high fever with chills and shivering (classic pattern: every 48 hrs for vivax, irregular for falciparum)
- Severe headache
- Sweating after the fever breaks
- Anaemia, dark urine
- Severe cases (falciparum): cerebral malaria, kidney failure, jaundice
Tests
- Rapid diagnostic test (RDT) — 20 minutes, low cost
- Peripheral smear (gold standard) — read by trained microscopist
- Test during fever for best yield
Treatment
Vivax: chloroquine + primaquine (14-day course to prevent relapse). Falciparum: artemisinin combination therapy (ACT). Always complete the full course — incomplete malaria treatment is the leading cause of drug-resistant parasites.
Leptospirosis — the flood-water disease
Caused by Leptospira bacteria, carried in rat urine that contaminates floodwater. Bacteria enter through cuts on the skin (especially feet/legs after wading), or through eyes/nose/mouth. Common in Mumbai, Chennai, Kerala, coastal Karnataka after heavy rain.
Symptoms
- High fever (after 5–14 days of exposure)
- Severe calf muscle pain (very characteristic)
- Red eyes (conjunctival suffusion without discharge)
- Severe headache
- Jaundice (yellowing of skin/eyes) in severe cases
- Reduced urine output (kidney involvement)
- Cough with blood (pulmonary involvement)
Treatment
Mild: doxycycline 100 mg twice daily for 7 days. Severe: IV penicillin or ceftriaxone in hospital. Severe leptospirosis can cause kidney failure and ARDS — don't delay.
Typhoid and other waterborne illnesses
Monsoon flooding contaminates piped water and street food. Watch for typhoid (Salmonella Typhi), Hepatitis A and E, cholera, and gastroenteritis.
Typhoid symptoms
- Step-ladder fever rising over 5–7 days
- Severe headache, abdominal pain
- Constipation or diarrhoea
- "Typhoid tongue" (coated centre, red tip and edges)
- Rose spots on the trunk (rare in dark skin, but look)
Tests: Blood culture (gold standard, week 1), Widal (after day 7, can be misleading), Typhidot IgM/IgG. Treatment: Antibiotics (azithromycin or ceftriaxone). Avoid quinolones — resistance is high in India.
Hepatitis A and E
Spread by contaminated water and food. Symptoms: prodrome of fatigue and nausea, then jaundice (yellow eyes/skin), dark urine, pale stools. Mostly self-limiting. Hepatitis E in pregnancy is dangerous (high mortality) — pregnant women should be extra cautious about water sources.
Plain viral fever — when to relax, when to worry
The most common monsoon illness. Caused by various respiratory or gastrointestinal viruses. Usually mild and self-limiting in 3–7 days.
- Fever under 39°C that responds to paracetamol
- Body ache, mild headache
- Sore throat, dry cough, runny nose
- You can eat, drink, and walk to the bathroom
- Fever lasts more than 3 days
- Fever returns after seeming to settle
- Severe muscle/joint pain or eye pain
- Bleeding from anywhere
- Difficulty breathing, chest pain
- Severe abdominal pain
- Confusion, drowsiness, seizures
- Patient is a child under 5, elderly over 65, pregnant, or diabetic
Which blood tests, when
For any monsoon fever lasting more than 48 hours, ask for this panel:
- CBC (complete blood count) with platelet count
- Dengue NS1 (days 1–5) or IgM (after day 5)
- Chikungunya IgM (after day 5)
- Malaria — RDT or peripheral smear
- Typhoid — blood culture (best) or Widal/Typhidot
- Urine routine + culture if urinary symptoms
- Liver function test if jaundice or abdominal pain
- Leptospirosis IgM if flood-water exposure
Cost: ₹800–2,500 for the basic monsoon panel at private labs. Free at most government hospitals and PHCs. Government RT-PCR for viral isolation also available where indicated.
Prevention checklist
Mosquito control (dengue, chikungunya, malaria)
- Every Sunday: dry day. Empty all water containers — flower pots, coolers, water tanks, tyres, bottles, AC trays.
- Mosquito nets at night (especially for children, elderly, pregnant women)
- Window screens; door sweeps
- Full-sleeve clothing in the evening
- Repellent with DEET 20%+, picaridin or IR3535
- Mosquito coils/vaporisers indoors
- Allow municipal fogging to access your premises
Waterborne disease prevention (typhoid, hepatitis, gastro)
- Drink only boiled or RO-filtered water
- Avoid street food, cut fruits, juices from open carts during monsoon
- Wash all fruits and vegetables in salt water
- Eat freshly cooked hot food
- Hepatitis A and Typhoid vaccines for children — consult paediatrician
- Wash hands with soap before every meal
Flood-water exposure (leptospirosis)
- Avoid wading through floodwater whenever possible
- If you must wade, wear rubber boots and waterproof bandages on any cuts
- Shower immediately after exposure
- Prophylactic doxycycline only on doctor's advice during major flooding
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Find a Doctor →Frequently asked questions
Which diseases peak during the Indian monsoon?
Dengue (Aug–Oct), chikungunya (Aug–Nov), malaria (Jul–Oct), leptospirosis (Jun–Sep), typhoid (Jun–Sep), Hepatitis A and E, gastroenteritis, cholera, and viral fevers all peak during monsoon. Respiratory infections and asthma flare-ups also rise.
What's the difference between dengue and chikungunya?
Both spread by Aedes mosquitoes. Dengue causes severe muscle pain, low platelets, and bleeding/shock risk. Chikungunya causes severe joint pain that can last weeks or months, but rarely drops platelets dangerously. If joint pain lingers, suspect chikungunya. If you have plasma-leak signs (bleeding, abdominal pain), suspect dengue.
When should I be hospitalised for dengue?
Immediately if platelet count falls below 50,000/μL, severe abdominal pain, persistent vomiting, restlessness or lethargy, bleeding gums or nosebleeds, blood in vomit/stool, cold clammy hands, rapid weak pulse, or reduced urine. Day 4–6 of fever is the highest-risk window. Get daily CBC from day 3.
How is leptospirosis caught and treated?
Caught by walking through floodwater contaminated with rat urine — bacteria enter through cuts or eyes/nose. Symptoms (5–14 days later): high fever, severe calf muscle pain, red eyes, jaundice, kidney failure in severe cases. Treatment: doxycycline (mild) or IV penicillin (severe). If you waded floodwater in the past 2 weeks and develop fever + calf pain, get tested.
Can I prevent dengue with insect repellent alone?
Repellents help but aren't enough. Aedes mosquitoes bite during the day. Layered prevention: weekly dry day (empty all water containers), mosquito nets at night, window screens, full-sleeve clothing in the evening, DEET 20%+ or picaridin repellent, mosquito coils indoors, plus municipal fogging.
Should I take antibiotics for monsoon viral fever?
No. Most monsoon fevers (dengue, chikungunya, viral fever) are viral — antibiotics don't work and can harm. See a doctor to confirm. Antibiotics are only for bacterial illnesses like typhoid, leptospirosis and bacterial pneumonia, and only after testing.
What blood tests should I get for monsoon fever?
CBC with platelets, dengue NS1 (days 1–5) or IgM (day 5+), chikungunya IgM (day 5+), malaria RDT/smear, Widal or Typhidot for typhoid, urine routine, liver function if jaundice suspected. Cost ₹500–2,000 in private labs; free in government hospitals.
Are children and elderly at higher risk?
Yes. Children under 10 and adults over 60 have highest risk of severe dengue, severe leptospirosis (kidney failure), and dehydration. Pregnant women are at high risk of severe malaria. Diabetics face higher complications across all. Test and hospitalise these groups earlier.