What Is Measles? How Measles and Rubella Differ, Whether It Can Be Fatal, and How a Dermatologist Tells 6 Fever-and-Rash Illnesses Apart
Measles (also called rubeola) is a viral infection caused by a Morbillivirus that brings a high fever, cough, runny nose and red eyes, followed by a red rash that starts at the hairline behind the ears and spreads down the face and trunk to the feet within about three days. Rubella (German measles) is a completely different disease caused by a different virus, even though the similar names have confused many people.
The most important difference comes down to two sentences. Measles makes people sicker, causes a heavier rash, and can kill through its complications. Rubella is so mild in most people that many never realize they have it, but if it occurs in the first three months of pregnancy it can cause birth defects in up to 90% of babies. The danger of the two diseases lies in different places, which is why they must be told apart.
This article is written from a dermatologist's point of view, because what brings patients to the clinic is a "rash", not a disease name. In Thailand there are at least six fever-and-rash illnesses that look so alike that the naked eye struggles to separate them: measles, rubella, roseola, dengue fever, scarlet fever and drug rash. The order in which the rash appears relative to the fever is the quickest key to telling them apart.
What causes measles, and how contagious is it?
Measles is caused by the measles virus, an RNA virus in the family Paramyxoviridae, genus Morbillivirus. It has a single strain, no animal carrier, and humans are its only reservoir. That is the theoretical reason the disease could be "eradicated worldwide" if vaccination coverage were high enough.
Measles is one of the most contagious diseases known to humans. Its basic reproduction number is about 12–18, meaning one patient can infect 12–18 people who have no immunity, compared with only about 1–2 for influenza.
How it spreads — tiny airborne droplets that hang in the air, not just the large droplets of mucus and saliva that fall to the floor as with an ordinary cold.
The virus can stay in the air and on surfaces for up to 2 hours after the patient has left the room, so people can be infected by sharing a room at different times.
When it is contagious — from 4 days before the rash appears until 4 days after. The most contagious period is the one before the rash, when everyone thinks it is just a cold.
Chance of infection after exposure without immunity — above 90%.
Measles vs rubella — a side-by-side comparison
This is the heart of the article. Both are fever-and-rash illnesses in which the rash begins at the face and moves downward, but almost everything else differs.
Cause — measles is caused by the measles virus (Measles morbillivirus) · rubella is caused by the rubella virus, which belongs to an entirely different family.
Incubation period — measles 7–14 days · rubella 14–21 days.
Fever — measles brings a high fever, often 39–40 °C, and the child looks clearly ill · rubella brings a low fever or none at all, and the child still plays and eats normally.
Symptoms before the rash — measles has the "three Cs" (cough, coryza or runny nose, and conjunctivitis or red eyes) for 3–4 days beforehand · rubella has almost no early symptoms, and the rash is often the first thing noticed.
Spots in the mouth — measles has Koplik spots, small white spots on the lining of the cheeks, a sign specific to measles alone · rubella has none.
Appearance of the rash — measles gives a deep red, slightly raised rash so dense that the patches merge into large blotches · rubella gives a pale pink, fine rash of separate spots that rarely merge.
Duration of the rash — measles 5–6 days, then it fades to brown and sheds as fine scales · rubella about 3 days, then it clears completely without leaving marks, which is why it is nicknamed "three-day measles".
Lymph nodes — measles causes no marked enlargement · rubella causes clear swelling behind the ears, at the back of the head and at the back of the neck, often 5–10 days before the rash. This is one of the best distinguishing points.
Joint pain — uncommon in measles · very common in adult women with rubella, up to about 70%, usually in the finger joints, wrists and knees.
Severity in the general population — measles is clearly more severe · rubella is very mild, and about half of those infected have no symptoms at all.
Main danger — measles is dangerous because of complications, especially pneumonia and encephalitis · rubella is dangerous to the unborn baby, not to the patient.
Vaccine — both are prevented by the same vaccine, MMR.
What does the measles rash look like, and why does its direction matter?
Appearance — a flat to slightly raised (maculopapular) rash, deep red to reddish-brown, with spots 3–5 millimetres across, so dense that they merge into large patches, especially on the face and upper trunk.
Direction — it always starts at the hairline and behind the ears, then spreads to the forehead, face, neck, trunk and arms, and reaches the palms and soles last. It takes about 3 days to move down the whole body.
Timing relative to fever — the measles rash appears while the fever is still high, not after it breaks. This separates measles from roseola immediately.
When it fades — it fades in the same order in which it appeared, with the face clearing first and the legs last, leaving brownish discoloration for about 1–2 weeks followed by fine scaling.
Itch — measles itches little or not at all. If the rash itches a lot, think of a drug rash instead.
Koplik spots — a sign that appears 1–2 days before the rash
Koplik spots are grey-white dots the size of a grain of salt on the red background of the lining of the cheeks, usually opposite the upper molars.
They are specific to measles and are not seen in any other fever-and-rash illness. If you see them, measles is almost confirmed.
They appear 1–2 days before the rash on the body and last only about 2–3 days, so they have often disappeared by the time the patient comes in because of the rash.
If a child has a high fever with cough, runny nose and red eyes, always open the mouth and look at the inside of the cheeks with a flashlight, because finding these spots allows isolation and protection of those around the child several days sooner.
The stages of measles, from infection to recovery
Incubation period, 7–14 days — no symptoms, and not contagious in the early part.
Prodromal stage, 3–4 days — the fever climbs to 39–40 °C together with a dry cough, runny nose and red eyes that are sensitive to light · Koplik spots appear at the end of this stage · this is the most contagious period.
Rash stage, 3–5 days — the rash spreads from the hairline down to the feet, and the fever usually peaks on the first day of the rash.
Recovery stage — the fever falls within 2–3 days after the rash covers the whole body. If the fever has not dropped by then or comes back, always suspect a complication; it is not a normal part of the illness.
Discoloration and scaling — these last another 1–2 weeks and clear on their own without treatment.
From the first fever to recovery takes about 7–10 days when there are no complications.
What are the symptoms of rubella?
Appearance — a pale pink, fine rash of flat or slightly raised spots that starts on the face and spreads down the trunk within a day, then clears within 3 days without leaving dark marks.
Cause — the rubella virus, also spread by droplets but much less contagious than measles.
Accompanying signs that help tell it apart — swollen, tender lymph nodes behind the ears, at the back of the head and at the back of the neck, often felt several days before the rash · a low fever · joint pain, especially in adult women · and in some people small red spots on the soft palate.
Severity and urgency — in children and healthy adults it is mild, clears on its own in 3–5 days, and almost never causes serious complications. About half of those infected have no symptoms at all.
When to see a doctor — if rubella is suspected in a pregnant woman, or in someone who has been in contact with a pregnant woman, treat it as urgent right away. It is no longer a mild illness in that situation.
🔴 Rubella and pregnancy — the real risk of this disease
All of the danger of rubella is concentrated in the unborn baby, not in the person who is infected. The condition is called congenital rubella syndrome, and the risk depends clearly on the gestational age when the mother is infected.
Infection before 11 weeks of pregnancy — the baby can have abnormalities in up to about 90% of cases.
11–16 weeks of pregnancy — the risk falls to about 10–20%, and the most common abnormality is deafness.
16–20 weeks of pregnancy — the risk is very low and is usually limited to hearing impairment.
After 20 weeks — abnormalities are almost never seen.
The three classic abnormalities are sensorineural deafness · congenital cataract · and congenital heart disease, particularly patent ductus arteriosus and pulmonary artery stenosis. Small head size, enlarged liver and spleen, low platelets and delayed development are also seen.
What can really be done is prevention in advance, not treatment after infection, because once the baby is infected there is no way to reverse it. Women of childbearing age who are unsure of their vaccination history should have their immunity tested and complete the vaccination before becoming pregnant. Because the MMR vaccine is a live attenuated vaccine, it must not be given during pregnancy, and contraception should continue for at least 1 month after the injection.
4 other fever-and-rash illnesses most often confused with measles
Roseola (roseola infantum)
Appearance — a high fever for 3–5 days while the child can still play, then the fever returns to normal first and the rash follows. It is a pale pink rash mainly on the trunk and clears in 1–2 days.
How to tell it from measles — the order is completely reversed. In measles the rash appears while the fever is still high; in roseola it appears after the fever has gone.
Urgency — low. It is most common in children aged 6 months to 2 years.
Dengue fever
Appearance — a persistent high fever for 2–7 days, marked body aches, pain behind the eyes, and a red rash all over with small islands of normal-coloured skin, together with tiny bleeding spots under the skin.
How to tell it apart — no cough or runny nose beforehand as in measles, and a blood test shows low platelets.
Urgency — high. The dangerous period is when the fever starts to fall, not when it is at its highest · read more at What does a dengue rash look like, does it itch, and how many days does it last?
Scarlet fever
Appearance — a fine red rash all over the body that feels like sandpaper, a red bumpy tongue like a strawberry, and unusual paleness of the skin around the mouth, following a sore throat caused by streptococcus bacteria.
How to tell it apart — rough skin, no red eyes, and a response to antibiotics, which measles does not have.
Urgency — moderate. Antibiotics are needed to prevent rheumatic fever.
Morbilliform drug eruption (a measles-like drug rash)
Appearance — a red rash all over the body that looks so much like measles that it takes its name from it, but it usually starts on the trunk and spreads outward, and itches clearly.
How to tell it apart — no preceding three Cs, no Koplik spots, and it is often linked to a drug started 4–14 days earlier.
Urgency — it must always be separated from a severe drug reaction. Peeling skin, mouth sores, red eyes with skin detachment, or facial swelling with enlarged lymph nodes is an emergency · read more at Drug allergy rash: symptoms, common types and how to cope
Chickenpox is easier to tell apart from this group because it forms clear fluid-filled blisters on a red base that appear at different times, so new blisters, fluid-filled blisters and scabs are all seen on the body together, and it itches a lot, completely unlike the flat rash of measles · see details at Chickenpox: causes, symptoms and treatment
Can you die from measles? The numbers worth knowing
The straight answer is yes, it can be fatal, but the chance is low with good care and no other risk factors. The measles virus itself does not kill; the complications do.
In countries with good public health systems, the death rate is about 1–2 per 1,000 patients, or roughly 0.1–0.2%.
Where children are malnourished or lack vitamin A, this figure can rise to 3–6%, many times higher.
The leading cause of death is pneumonia, not the fever or the rash.
The groups at highest risk of death are children under 5, adults over 20, pregnant women, people with weakened immunity, and people with vitamin A deficiency.
By contrast, rubella almost never causes death in the patient. Its losses fall on the unborn baby instead.
What to take from these numbers is not fear but the fact that almost all of the risk is preventable with two inexpensive vaccine doses that are already part of Thailand's national immunization programme.
Complications of measles, in order of frequency
Middle ear infection — seen in about 7–9%, the most common complication, and a cause of permanent hearing loss.
Diarrhoea — seen in about 8%, and most dangerous in young children because of dehydration.
Pneumonia — seen in about 1–6%. It is the leading cause of death from measles. It may be caused by the measles virus itself or by bacteria that complicate it later.
Laryngitis and bronchitis (croup) — causing a barking cough and noisy breathing, most common in young children.
Acute encephalitis — seen in about 1 in 1,000 cases, usually within 2 weeks after the rash appears, with drowsiness, seizures or confusion, and it can leave permanent brain damage.
Temporary suppression of immunity for several weeks to several months — this is why children often catch other infections again after recovering from measles. The phenomenon is called immune amnesia.
The sign that a complication is developing is a fever that does not fall within 2–3 days after the rash covers the whole body, or a fever that falls and then returns. If you remember only one sentence, remember this one.
SSPE — a complication that arrives years later
Subacute sclerosing panencephalitis is a condition in which the virus hides in the brain and causes disease 7–10 years later, leading to behaviour changes, memory loss, muscle jerks and steady decline until death. There is still no effective treatment.
It occurs in about 1 in 10,000 measles patients.
The risk is much higher if infection occurs before the age of 2, which is an important reason to protect babies through the herd immunity of the people around them, because young children cannot be vaccinated until they reach the right age.
This condition is not caused by the vaccine. It results only from natural measles infection.
Measles in adults — how it differs from children
Measles is not only a children's disease, and in adults it is usually worse.
More severe symptoms — a higher fever, a heavier rash and longer-lasting exhaustion.
More complications — especially pneumonia and hepatitis, which are clearly more common in adults than in children.
Who is commonly affected in Thailand now — working-age adults who did not receive the full two vaccine doses, or who received one dose in childhood and whose immunity has since waned.
Who should have immunity tested or receive a booster — healthcare workers, teachers and childcare staff, people travelling to outbreak areas, and women planning a pregnancy.
How doctors diagnose measles and rubella
From symptoms and examination — a high fever with the three Cs, followed by a rash spreading from the hairline to the feet. Finding Koplik spots makes the picture clearer still.
Blood test for antibodies — IgM against the measles or rubella virus, which can usually be detected from the day the rash appears for about 1 month · testing too early, in the first days, may give a negative result even when the disease is present.
Testing for the virus's genetic material — from a throat or urine sample, used for confirmation and for investigating outbreaks.
Measles is a notifiable disease under the Ministry of Public Health surveillance system. Confirmation is therefore not only about one patient but also about controlling the outbreak around them.
For a pregnant woman who has been in contact with a rubella patient, immunity must be tested as soon as possible and an obstetrician consulted. Do not wait to see whether symptoms develop.
How is measles treated, and the vitamin A many people do not know is a treatment
There is no antiviral drug that treats measles directly. The main treatment is supportive care to help the body get through the infection, but there is one specific treatment that the World Health Organization recommends for every child with measles: vitamin A, which significantly reduces deaths and eye complications.
Oral vitamin A — given once a day for 2 consecutive days
Under 6 months — 50,000 international units per dose
6–11 months — 100,000 international units per dose
12 months and over — 200,000 international units per dose
If there are clear signs of vitamin A deficiency, such as dry eyes or a cloudy cornea, a third dose is given again 2–4 weeks later.
The rest of the supportive care
Paracetamol reduces fever and body aches. The dose for children is 10–15 milligrams per kilogram of body weight per dose, every 4–6 hours, no more than 5 times a day.
Give enough fluids — a high fever together with diarrhoea causes dehydration faster than you might expect. Check that the child passes urine at least every 6–8 hours.
Antibiotics are used only when a secondary bacterial infection develops, such as a middle ear infection or pneumonia. They are not given "just in case" in measles without complications, because they do not reduce infection but do increase drug-resistant bacteria.
Eye care — red eyes and sensitivity to light are a normal part of the illness. Keep the child in a room without glaring light, and see an eye doctor if the eyes hurt a lot or vision is abnormal.
Signs that care is going well are a fever that falls within 2–3 days after the rash covers the whole body, and eating, drinking and passing urine well. Signs that it is not working are a fever that stays high, a fever that comes back, fast or laboured breathing, drowsiness or seizures. The choice of medicines and the decision to admit to hospital always belong to the doctor.
Medicines to be careful with, and common myths about measles
Do not give aspirin to children and teenagers with a viral fever, because of the risk of Reye syndrome, which seriously damages the liver and brain.
Do not give antibiotics on your own, thinking they will help recovery — measles is caused by a virus, and antibiotics have no effect on the disease.
"You must not bathe when you have measles" is not true — bathing normally with warm water and mild soap is fine. Clean skin helps reduce secondary bacterial infection.
"You must take a medicine to push all the rash out" does not exist in medicine — the rash will come out fully and fade by itself according to the stages of the illness.
"If you have had measles you cannot get rubella" is not true — they are different viruses with different immunity. Having had one disease gives no protection against the other.
"A vaccinated child cannot get measles" is not entirely right — two vaccine doses protect about 97%, and the small number who are still infected usually have milder illness and are much less contagious.
The MMR vaccine — one injection protects against both measles and rubella
The measles–mumps–rubella (MMR) vaccine is a live attenuated vaccine that protects against both diseases in this article at the same time.
Effectiveness — one dose protects against measles about 93% · two doses about 97% · for rubella, one dose protects about 97%.
Schedule in Thailand's national immunization programme — the first dose at 9–12 months and the second at 1 year 6 months. Always check with the vaccination record and your regular doctor, because the schedule is adjusted from time to time.
Adults who were never vaccinated or are unsure — can receive 2 doses at least 4 weeks apart, or have immunity tested first.
Important contraindications — it must not be given during pregnancy, and pregnancy should be avoided for at least 1 month afterwards · people with severely weakened immunity need individual assessment by a doctor.
Possible side effects — a low fever and a faint rash around day 5–12 after the injection, which clear on their own and are not contagious · the MMR vaccine does not cause autism. The original study that claimed this was retracted and shown to be based on false data in 2010, and studies following several hundred thousand children since then have found no link.
What to do after contact with a measles patient
Prevention after exposure has a very strict time window, and being late by just a few days means it no longer works.
MMR vaccine within 72 hours of exposure — can prevent the disease or reduce its severity in people who can be vaccinated.
Immunoglobulin within 6 days of exposure — for people who cannot receive a live vaccine: babies under 12 months, pregnant women without immunity, and people with severely weakened immunity.
Watch for symptoms until day 21 after exposure, because the incubation period can last up to 2 weeks.
If symptoms appear, phone the healthcare facility before arriving so that an isolation room can be prepared. Do not walk in and sit in the general waiting room with other people.
Home care, and how many days to isolate
Isolate until 4 days after the rash appears in people with normal immunity · people with weakened immunity are contagious for much longer, and the doctor must set the period.
Keep the patient in a separate, well-ventilated room and keep people without immunity, especially babies and pregnant women, away.
Drink often and give soft, easy-to-eat food, because the mouth and throat are often sore during the high fever.
Rest fully and stay off school or work until the contagious period has passed.
Normal skin care — the measles rash needs no special medication. A moisturiser can be used as usual when the skin starts to peel, and there is no need to scrub or rub to make the scales come off sooner.
Danger signs that need hospital care immediately
Fast or laboured breathing, chest indrawing, or blue lips
Drowsiness, being hard to wake, confusion, or seizures
A fever that does not fall within 2–3 days after the rash covers the whole body, or a fever that falls and then returns
Severe ear pain, or pus draining from the ear
Severe diarrhoea, vomiting so much that the child cannot eat, a dry mouth, or clearly reduced urine
Severe eye pain, blurred vision, or a cloudy cornea
The rash turning into pustules, skin peeling in sheets, or mouth sores so painful that the person cannot eat
The patient is a baby under 1 year, a pregnant woman, or a person with weakened immunity — this group should see a doctor as soon as measles is suspected, without waiting for danger signs
When to see a dermatologist rather than wait and see
A rash all over the body where you cannot tell whether it is a viral fever-and-rash illness or a drug rash, especially when a new medicine was started 4–14 days earlier
A red rash all over the body with skin peeling in sheets, mouth sores, red eyes, or a swollen face — treat it as a skin emergency until proven otherwise
A rash that has not faded at all after more than 1 week, or that comes back after clearing
Dark marks after the rash that have not faded after 2–3 months
A rash all over the body in an adult with no preceding fever, which is usually not measles and needs another cause to be found, such as secondary syphilis rash, which appears on the palms and soles and does not itch
Clear fluid-filled blisters that appear at different times across the body, which point to chickenpox or hand, foot and mouth disease rather than measles
See other skin conditions at the Skin Conditions overview page.
In brief
Measles and rubella are different diseases caused by different viruses. The similar names are a matter of language, not of the germs.
Measles makes people sicker: a high fever, the three Cs for 3–4 days beforehand, Koplik spots in the mouth, and a deep red rash that merges into blotches and spreads from the hairline to the feet, then fades leaving dark marks and scaling.
Rubella is much milder: a low fever and a pale pink rash that clears in 3 days. The hallmarks are swollen lymph nodes behind the ears and at the back of the head, and joint pain in adult women.
The danger of the two diseases lies in different places: measles is dangerous through the patient's own complications, especially pneumonia, the leading cause of death · rubella is dangerous to the unborn baby, up to about 90% if the mother is infected before 11 weeks of pregnancy.
It can be fatal, but the chance is low with good care: about 1–2 per 1,000 cases in a good public health system, and many times higher in malnourished children or those lacking vitamin A.
Vitamin A is a specific treatment that many people do not know about: given once a day for 2 days in a row, at doses set by age, together with supportive care for fever and fluids.
The one thing to do right away: if there is a high fever with cough, runny nose and red eyes, and a rash starts at the hairline behind the ears while the fever is still high, isolate and phone the healthcare facility before going. And if a pregnant woman has been in contact with a rubella patient, have her immunity tested immediately without waiting for symptoms.
Frequently asked questions
What causes measles?
It is caused by the measles virus, an RNA virus of the genus Morbillivirus, which has a single strain and only humans as its reservoir. The virus is in the nasal mucus, saliva and phlegm of patients and spreads through tiny airborne droplets that can hang in the air for up to 2 hours after the patient has left the room, so sharing a room at different times can still lead to infection. Measles is one of the most contagious diseases known: one patient can infect 12–18 people without immunity, and the chance of infection after exposure without immunity is above 90%. Patients are contagious from 4 days before the rash appears until 4 days after. The most contagious period is when it still looks like an ordinary cold.
Does measles go away on its own?
In healthy people without complications, measles clears on its own within about 7–10 days, because the body can clear the virus by itself and there is no antiviral drug for direct treatment. But "clears on its own" does not mean no care is needed. What kills measles patients is not the fever or the rash but the complications, especially pneumonia, middle ear infection, diarrhoea with dehydration, and encephalitis. In addition, the World Health Organization recommends vitamin A for every child with measles because it genuinely reduces deaths. Those who should not be left to recover at home are babies under 1 year, adults, pregnant women and people with weakened immunity.
How many days does the measles virus survive?
This needs to be split into two questions. The first is how long the virus lasts outside the body: it can hang in the air and stay on surfaces for up to about 2 hours after the patient coughs or sneezes, which is much longer than most respiratory viruses. The second is how many days a patient is contagious: from 4 days before the rash appears until 4 days after, about 8 days in all. People with weakened immunity may be contagious for much longer. The incubation period after exposure is 7–14 days, so watch for symptoms until day 21 after contact with a patient.
How many days does it take for a child to recover from measles?
The measles rash takes about 3 days to spread from the hairline down to the feet, stays on the body for about 5–6 days, then fades in the same order, with the face clearing first and the legs last. The fever usually falls within 2–3 days after the rash covers the whole body. From the first fever to full recovery takes about 7–10 days. After the rash fades, brownish marks and fine scaling remain for another 1–2 weeks, which clear on their own without treatment and are not a sign that the virus is still present. What to watch for is a fever that does not fall within 2–3 days after the rash is complete, or a fever that falls and then returns. That is a sign of a complication, and the child must go back to the doctor.
What are the symptoms of measles in a child?
It starts with a fever that gradually climbs to 39–40 °C, together with the symptoms easily remembered as the three Cs: a dry cough, a blocked or runny nose, and red eyes that are sensitive to light. This group of symptoms comes 3–4 days before the rash and is often mistaken for an ordinary cold. Toward the end of this period Koplik spots may appear, small white dots the size of a grain of salt on a red background inside the cheeks, which are seen only in measles. Then a deep red rash begins at the hairline and behind the ears while the fever is still high, and spreads down the face, trunk and feet within about 3 days. The measles rash itches little or not at all. If it itches a lot, think of a drug rash instead.
What are the symptoms of measles in adults?
The main symptoms are the same as in children: a high fever, the three Cs, Koplik spots, and a rash spreading from the hairline to the feet, but in adults it is usually clearly worse, with a higher fever, a heavier rash, longer exhaustion and more complications, especially pneumonia and hepatitis, which are more common in adults than in children. Those commonly affected in Thailand now are working-age adults who did not receive the full two vaccine doses, or who received only one dose in childhood and whose immunity has waned over time. Adults who should have immunity tested or receive a booster are healthcare workers, teachers and childcare staff, people travelling to outbreak areas, and women planning a pregnancy, who should finish vaccination at least 1 month before becoming pregnant.
References
World Health Organization. Measles fact sheet and Rubella fact sheet.
Centers for Disease Control and Prevention. Measles (Rubeola) and Rubella — Clinical Overview, Complications, Vitamin A treatment.
American Academy of Pediatrics. Red Book: Report of the Committee on Infectious Diseases — Measles, Rubella.
Pediatric Infectious Disease Society of Thailand. Measles.
Division of Epidemiology, Department of Disease Control, Ministry of Public Health. Guidelines for measles surveillance, investigation and control.
Bolognia JL, Schaffer JV, Cerroni L. Dermatology — Exanthematous Viral Diseases.
Written by Dr. Patara Voravutinon, Dermatologist · Last reviewed 18 September 2026
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