Dengue is a viral infection spread by Aedes mosquitoes, which bite mainly during the day and breed in small pools of clean standing water around homes. In Ho Chi Minh City cases rise sharply in the rainy season, roughly from May to November. Most children recover, but a small proportion become seriously ill, usually around the time the fever starts to fall, so the key for parents is to know the warning signs and to see a doctor early whenever a child has a high fever.
For families new to the tropics, dengue can sound frightening and abstract at the same time. This guide explains how the illness typically unfolds, why the day the fever breaks needs the closest attention, which medicines doctors usually avoid, how to cut mosquito breeding around an apartment or house, and what to ask your preschool about its own prevention routine. It is general information; a doctor who examines your child and orders blood tests is the person who can tell you what is happening in a particular case.
How dengue spreads and why the rainy season matters
Dengue is caused by four closely related viruses, called serotypes. It passes from person to person through the bite of an infected Aedes mosquito, most often Aedes aegypti, a small dark mosquito with white markings on its legs. Unlike the mosquitoes that whine around the bed at night, Aedes mosquitoes are most active in the early morning and late afternoon, and they bite indoors as well as outdoors. That means the hours a child spends at home after school, or on a shaded balcony, matter as much as the night.
Aedes mosquitoes breed in small containers of fairly clean water: plant saucers, buckets, discarded cups, blocked gutters, the tray under a refrigerator, water jars and the folds of a tarpaulin. During Saigon’s rainy season, short heavy showers almost every afternoon refill these containers constantly, and eggs can hatch within days. Cases in southern Vietnam therefore tend to climb during the wet months, although dengue is present all year.
Dengue is not only a problem in poorer neighbourhoods or on the outskirts. Aedes mosquitoes do well in dense, modern districts too, wherever there are balconies full of potted plants, construction sites with puddles, rooftop water tanks and drains that clog after storms. A tidy apartment on a high floor reduces exposure but does not remove it, because these mosquitoes travel in lifts and stairwells and breed in shared corridors and car parks. Families who move from one part of the city to another often find the same advice applies.
Because there are four serotypes, a person can have dengue more than once. Infection with one serotype gives lasting protection against that one but not against the others, and a second infection with a different serotype carries a higher risk of severe disease. For families planning to stay in Vietnam for several years, that is a reason to take prevention seriously even after a mild first episode.
How the illness usually unfolds
Doctors and the World Health Organization describe dengue in three phases. Timing varies between children, and some children have only a mild illness that is never diagnosed, but the pattern helps parents understand why doctors may want to see a child again even when the fever has gone.
| Phase | Typical timing | What parents may see | Why it matters |
|---|---|---|---|
| Fever phase | First 2–7 days | Sudden high fever, flushed face, headache, body aches, poor appetite, sometimes vomiting or a rash | Hard to tell apart from other viral fevers without a blood test |
| Critical phase | Often around days 3–7, as the fever falls | Child may seem better at first, or become tired, restless, with stomach pain or vomiting | In severe cases blood vessels leak fluid; this is when dangerous complications appear |
| Recovery phase | The following days | Appetite returns, energy improves; some children get an itchy rash | Fluid moves back into the bloodstream; doctors still watch the child |
The middle row is the reason dengue catches families out. A falling temperature usually means a child is getting better, but in dengue it can coincide with the most dangerous period. Doctors often ask to see the child daily during these days and may repeat blood tests to follow platelet counts and the concentration of the blood.
Warning signs that mean going to hospital now
If your child has had a fever in the past few days and shows any of the following, take them to a hospital emergency department without waiting for the next appointment. These signs are drawn from World Health Organization guidance used in Vietnam.
- Stomach pain or tenderness, especially if it is getting worse.
- Vomiting that keeps happening, or not being able to keep fluids down.
- Bleeding from the gums or nose, blood in vomit or stool, or new bruises and pinpoint red spots on the skin.
- Unusual sleepiness, floppiness, confusion, or restlessness and irritability you cannot settle.
- Cold, clammy or mottled hands and feet, or a child who looks pale and unwell.
- Passing very little urine, for example no wet nappy or no visit to the toilet for many hours.
- Fast or difficult breathing.
Severe dengue can be treated, and outcomes depend heavily on getting fluids and monitoring at the right time. Families sometimes delay because the fever has gone and they assume the worst is over. If your child seems worse as the fever falls, that is exactly the moment to go in. In an emergency the ambulance number in Vietnam is 115.
Fever, medicine and what to avoid
See a doctor early for a high fever. In a city where dengue is common, a high fever in a young child is worth a medical visit within the first day or two, even if it may turn out to be a different virus. A blood test can help confirm dengue, and the doctor will explain what to watch for and when to return.
Ask about paracetamol, and avoid aspirin and ibuprofen unless a doctor says otherwise. Health authorities including the World Health Organization advise using paracetamol, also called acetaminophen, for fever and pain in suspected dengue, and avoiding aspirin and anti-inflammatory medicines such as ibuprofen because they can increase the risk of bleeding. Ask your doctor for the right dose for your child’s weight; do not rely on a pharmacy guess.
Fluids matter more than food. Encourage regular drinking: water, milk, soups, fruit juice diluted with water or oral rehydration solution if advised. Keep a rough log of drinks and urine so you can tell the doctor whether your child is keeping up.
Be wary of unproven remedies. Well-meaning neighbours may suggest herbal drinks or leaves said to raise platelet counts. There is no reliable evidence that these replace medical care, and some can upset the stomach of a sick child. Mention anything you plan to give to the doctor first.
Rest at home and stay away from preschool. A child with dengue needs rest and close observation, not a full school day. The school does not need to exclude classmates, because dengue does not spread directly from child to child, but it will want to know so it can check its grounds for breeding sites.
Cutting mosquito breeding at home: a weekly routine
Prevention around the home is unglamorous but effective, because Aedes mosquitoes rarely fly far from where they hatch. Doing these steps once a week breaks the breeding cycle, since eggs need roughly a week or more to become adult mosquitoes.
- Walk around the balcony, terrace, garden and bathroom looking for anything that holds water: plant saucers, buckets, pet bowls, toys, unused pots and the drip tray under the refrigerator.
- Empty and scrub containers rather than just tipping them, because eggs stick to the inner walls above the waterline.
- Turn buckets and toys upside down, and keep stored water in containers with tight lids.
- Change water in vases and pet bowls at least weekly, and clean them.
- Check that gutters and balcony drains are not blocked after a storm.
- Fit screens on windows where possible and close doors to balconies in the late afternoon.
- Use a repellent suitable for young children on exposed skin when outdoors at dawn and dusk, and dress children in light long sleeves and trousers where practical.
Ask your landlord or building management about regular spraying in common areas, which some residential buildings in Ho Chi Minh City organise, especially when local cases rise. Spraying helps but does not replace removing standing water, because new mosquitoes keep hatching from any container that is missed.
What your preschool can do, and what to ask
Children spend many daylight hours at school, including the morning and late afternoon when Aedes mosquitoes are active, so the school grounds are part of the picture. Well-run preschools in Vietnam check outdoor play areas, plant pots, toy storage and drains for standing water, especially after rain, and many respond to local health warnings by stepping up cleaning and asking for spraying.
Useful questions on a tour or at a parent meeting are simple. How often is the outdoor area checked for standing water? Are water play trays emptied and dried at the end of each day? Are classroom windows screened, and are doors kept closed at the times mosquitoes are active? Is repellent applied at school, and if so, with what product and whose permission? Will parents be told if a case is reported in the class or among staff, so families can watch for fever?
If your child is diagnosed with dengue, tell the school. It cannot pass directly to classmates, but it suggests mosquitoes carrying the virus may be nearby, either at home or at school, and the school may want to check its grounds again. When your child returns, ask the teacher to let you know about any new fever, nosebleed or unusual tiredness, since recovery can take time and energy may stay low for a while.
Vaccination and repeat infections
Dengue vaccines have been developed in recent years, and at least one has been licensed in Vietnam for use in children from around four years old. Vaccines differ in who they are approved for, how many doses are needed and whether a previous infection matters. These are questions for your child’s doctor or a vaccination clinic, which can explain the current recommendation for your child’s age and history.
Whatever you decide about vaccination, mosquito prevention remains the basis of protection, because no vaccine is complete protection and mosquitoes also carry other infections. Keep a record of any confirmed dengue diagnosis, including the date and, if the laboratory reported it, the serotype. If your child has dengue again later, in Vietnam or elsewhere in the tropics, that history helps doctors judge the risk.
If your family travels during the year, remember that dengue is common across much of Southeast Asia, South Asia and Latin America. A fever that starts after a beach holiday in the region deserves the same attention as a fever at home in Saigon, and it helps to tell the doctor where you have been.
Families sometimes ask whether they should leave the city during peak season. For most families that is neither practical nor necessary. The more useful step is to agree as parents on a simple rule: a high fever means a doctor visit within a day or two, and a child who worsens as the fever falls means hospital.
Câu hỏi thường gặp
Can my child catch dengue from a classmate?
No, not directly. Dengue passes from person to person only through mosquito bites. A mosquito bites an infected person, becomes infected itself and can then bite someone else. That is why a case in a class is a reason to check for breeding sites rather than to exclude other children.
Why do doctors in Vietnam often order a blood test for a fever?
Early dengue looks like many other viral fevers. A blood test can detect the virus or antibodies and shows platelet counts and blood concentration, which help doctors judge how the illness is progressing. Repeated tests during the critical days help them spot early warning changes.
Is mosquito repellent safe for toddlers?
Several repellents are considered suitable for young children when used as directed, but age limits and concentrations differ by product and by country. Read the instructions, avoid hands and faces of young children who put fingers in their mouths, and ask your doctor or pharmacist which product suits your child’s age.
Are mosquito coils and plug-in devices enough at home?
They may reduce bites in a closed room, but they do not stop mosquitoes breeding nearby, and burning coils indoors adds smoke that young children should not breathe for long periods. Removing standing water, screens and clothing are more reliable foundations, with repellent for outdoor times.
How long after dengue can my child return to preschool?
There is no fixed exclusion rule, because dengue does not spread between children directly. Your child should return when the doctor is satisfied they have recovered and they have the energy for a full day. Many children feel tired for some time afterwards, so a gentle first week helps.
Does a mild case mean my child is protected?
Only against that particular serotype. There are four, and a later infection with a different one carries a higher risk of severe illness. Keep a note of the diagnosis and continue mosquito prevention, and tell any future doctor that your child has had dengue before.