Dengue usually starts suddenly with a very high fever, a severe headache, pain behind the eyes and aching muscles and joints, and the fever typically lasts 2 to 7 days. Typhoid tends to creep up more slowly, with a fever that keeps going beyond 3 days and often comes with stomach pain, constipation or diarrhoea and loss of appetite. The symptoms overlap a lot in the first few days, though, so the only reliable way to tell them apart is the right blood test on the right day.
This guide covers how the two fevers usually behave, which tests to ask for and when, why the Widal test so often misleads, and why starting antibiotics on your own is a bad idea in India right now.
How the two fevers usually behave
Dengue is a viral infection spread by mosquito bites. The WHO says symptoms usually begin 4 to 10 days after the bite and last 2 to 7 days. The fever can hit 40°C. Many people have only mild symptoms or none at all.
Typhoid is a bacterial infection (Salmonella Typhi) spread through food or water contaminated with faeces. The CDC gives an incubation period of 6 to 30 days. It starts gradually, and the fever can reach 39 to 40°C and usually lasts more than 3 days. Without treatment it can go on for weeks.
| Feature | Dengue | Typhoid |
|---|---|---|
| Cause | Virus, spread by mosquitoes | Bacteria, spread by contaminated food and water |
| Onset | Sudden, high fever from day 1 | Gradual, fever builds over days |
| How long fever lasts | Usually 2 to 7 days | More than 3 days, can last weeks if untreated |
| Typical symptoms | Severe headache, pain behind the eyes, muscle and joint pain, nausea, vomiting, rash, swollen glands | Weakness, stomach pain, headache, constipation or diarrhoea, cough, poor appetite, sometimes rose-coloured spots |
| Danger period | Often just as the fever goes away | Usually after 2 to 3 weeks of illness |
| Key early test | NS1 antigen (with IgM) | Blood culture |
| Antibiotics | Useless (it’s a virus) | Needed, chosen by a doctor |
A pattern isn’t a diagnosis. In Indian cities after the monsoon, both infections circulate at the same time, and malaria, scrub typhus and ordinary viral fevers look similar in the first days too. Your doctor may test for more than one.
The right test on the right day
Timing matters because each test looks for something different, and each has a window when it works best.
| Day of fever | Dengue test | Typhoid test |
|---|---|---|
| Days 1 to 5 | NS1 antigen (or RT-PCR), ideally with IgM | Blood culture, taken before any antibiotic |
| Days 5 to 7 | NS1 and IgM together | Blood culture |
| After day 7 | IgM antibody is the main test | Blood culture still the main test; your doctor may add others |
| Any day | CBC to track platelets and haematocrit | CBC, liver tests as your doctor advises |
Dengue: NS1 first, IgM later
The CDC’s testing guidance says that in the first 7 days of illness, doctors should order either an RT-PCR or an NS1 antigen test together with an IgM antibody test. NS1 can be as sensitive as RT-PCR in that window. IgM picks up most infections after day 3 and becomes the main test after day 7.
One thing to remember: a negative NS1 does not rule out dengue. If you test on day 6 and NS1 is negative, IgM may still be positive. A CBC tells your doctor how the illness is progressing. Our article on dengue platelet counts explains which numbers matter and why haematocrit and warning signs matter more than one platelet reading.
Typhoid: blood culture, not Widal
Blood culture is the main test for typhoid, according to the CDC’s clinical guidance. The lab grows the bacteria from your blood and then tests which antibiotics still work against it. That second part matters a great deal in India (more on this below). Ask for the sample to be taken before you start any antibiotic, since earlier doses can stop the bacteria growing in the lab.
The Widal test is still ordered widely in India because it’s cheap and fast. The CDC says serological tests such as Widal are not recommended because of their high false-positive rate. In places where typhoid is common, many people may already carry antibodies from past exposure, and other infections can give a false positive. A “positive Widal” on day 2 of a fever can lead to an unnecessary course of antibiotics while the real cause, sometimes dengue, goes unnoticed.
Why you shouldn’t start antibiotics on your own
It’s tempting to take leftover antibiotics or ask the chemist for “something for fever”. Here’s why that backfires:
- If it’s dengue, antibiotics do nothing. Dengue is a virus. You get the side effects without any benefit.
- The common choices often don’t work against typhoid any more. An Indian multicentre surveillance study published in Scientific Reports in 2025 tested 1,150 S. Typhi samples from eight hospitals in seven cities (2021 to 2024). Only 0.7% were still susceptible to ciprofloxacin. The researchers also found the dose of azithromycin needed to stop the bacteria creeping up each year, and a cluster of ceftriaxone-resistant typhoid in Ahmedabad.
- It muddles the test. Antibiotics taken before the blood sample can stop the culture from growing the bacteria, without curing the infection, which leaves your doctor guessing.
- Half-courses breed resistance. Stopping when you feel a bit better is how resistant strains get a head start.
The WHO notes that antimicrobial resistance in typhoid is common and makes treatment more complex and costly. Let a doctor choose the antibiotic, ideally guided by the culture report, and finish the course they prescribe.
Safe fever care while you wait for results
- Use paracetamol for fever and aches, at the dose on the label or as your doctor advises.
- Avoid ibuprofen, aspirin and other painkillers like them until dengue is ruled out. The WHO warns they raise the risk of bleeding in dengue.
- Drink plenty of fluids: water, ORS, coconut water, buttermilk, dal water, soups.
- Rest, and keep a simple log of temperature, fluids taken and how often you pass urine. It helps your doctor.
If diarrhoea is part of the picture, our guide to causes and treatment of diarrhoea covers ORS and dehydration signs.
The typhoid conjugate vaccine
Typhoid is preventable. The WHO says the typhoid conjugate vaccine (TCV) is given as a single injection to children from 6 months of age, and to adults up to 45 or 65 years, depending on the vaccine brand. Two older vaccines (an injection for those aged 2 and over, and an oral capsule for those over 6) need boosters because their protection doesn’t last long.
Ask your paediatrician whether your child has had TCV. Adults who eat out often or travel a lot can ask their doctor too. Vaccination doesn’t replace safe food and water. The WHO’s basics: drink safe water, eat food that’s thoroughly cooked and served hot, avoid ice unless it’s made from safe water, and drink only boiled or pasteurised milk. Our article on the risks of raw milk explains the last point.
For dengue, prevention is about mosquitoes: no stagnant water in coolers, pots or tyres, and repellent and full sleeves at dawn and dusk. Our post on preventing monsoon infections has more.
Go to hospital if…
Dengue warning signs. The WHO notes that severe dengue often appears after the fever has gone, so don’t relax just because the temperature drops. Go to hospital at once for:
- Severe stomach pain
- Vomiting that won’t stop
- Bleeding from the gums or nose, or blood in vomit or stool
- Fast breathing, restlessness, extreme tiredness or weakness
- Pale, cold skin or being very thirsty
Typhoid warning signs. The CDC notes that serious complications, including intestinal perforation, bleeding in the gut and confusion, usually appear after 2 to 3 weeks of illness. Go to hospital for:
- Sudden or severe belly pain, or a hard, swollen belly
- Blood in stools or black, tarry stools
- Confusion, extreme drowsiness or unusual behaviour
- Fever that keeps going or gets worse despite treatment
For any fever with fainting, breathing difficulty or a child who is very floppy or not drinking, call 112.
Frequently asked questions
Can you have typhoid and dengue at the same time?
Yes, it’s possible, especially after the monsoon when both are common. That’s one more reason to test properly rather than treat a single “positive” result.
My Widal test is positive. Do I have typhoid?
Not necessarily. Widal has a high false-positive rate, and the CDC doesn’t recommend it for diagnosis. Ask your doctor whether a blood culture is needed before treatment.
Which day should I get the NS1 test done?
NS1 works best in the first 7 days of fever, ideally paired with an IgM test. After day 7, IgM is the main test. A negative NS1 doesn’t rule out dengue.
Do typhoid patients have low platelets too?
Platelets can dip in several infections, so a low count alone doesn’t prove dengue. The combination of symptoms, NS1 or IgM, and blood culture gives the answer.
If I had the typhoid vaccine, can I still get typhoid?
Yes, it’s possible. No vaccine gives complete protection, and a closely related illness called paratyphoid fever can look the same. If you have a persistent fever, get tested even if you’re vaccinated.
This article is for general information and is not a substitute for advice from a doctor. If you have symptoms or a health condition, please consult a qualified healthcare professional.