If vaccination rates continue to fall in the United States, vaccine-preventable diseases will become more prevalent. Many vaccine-preventable diseases may be unfamiliar to healthcare providers and families. To prepare for the more frequent appearance of diseases that are now uncommon, over the next few months, the Vaccine Update feature article will review key reminders about specific vaccine-preventable diseases for healthcare providers and include resources available for sharing with families.
The February article will focus on measles. Measles is a highly contagious respiratory virus. It is so contagious that someone can be infected simply by occupying the space an infected person was in two hours earlier. As described by VEC Director, Dr. Paul Offit, “… very, very tiny droplets … hang in the air like a ghost …”
Before the vaccine was introduced in 1963, virtually everyone was infected by 15 years of age. The virus sickened 3 million to 4 million people in the U.S. each year, but with the introduction of the vaccine, measles was eliminated by 2000. Unfortunately, this elimination status remains tenuous. In 2024, the U.S. had 285 cases of measles and 16 outbreaks. This compared to 59 cases and four outbreaks in 2023. By the second week of February 2025, the U.S. has had two outbreaks and at least 61 cases as reported by state and local health departments.
While two doses of measles vaccine are protective (97% effectiveness), as soon as population vaccination rates drop below 95%, cases and outbreaks increase.
Recognizing measles
Patients with measles initially have symptoms that look like many upper respiratory infections. The most classic description is a high fever (104°F or 40°C) and the “three Cs”: cough, coryza (runny nose), and conjunctivitis (red, watery eyes). Another symptom that can occur is the development of Koplik spots, which are tiny, white “grains of sand” inside the mouth, particularly inside the cheeks and lips. Koplik spots typically appear 1–2 days before the body rash; however, while these spots are well described, they are rare, so their absence does not help rule out measles. The classic body rash appears 2-4 days after these initial symptoms. The period before development of the body rash is when virus in the bloodstream is at its peak. By the time the rash appears, an immune response is developing, and quantities of virus in the blood are declining. This presence of virus prior to and after rash development explains the defined transmission period of four days before to four days after appearance of the rash. Notably, the rash begins at the hairline and spreads downward. Once described by a senior clinician as “a bucket of rash” poured over a child’s head, this pattern of appearance can help with diagnosis. A classic measles rash has a mix of flat and raised red lesions. The rash tends to fade in the same order it appeared. Symptoms typically resolve over the period of about a week.
Making a measles diagnosis
Because measles starts off like many other infections, clinicians need to maintain a high level of suspicion. One of the first moments to consider measles is if a child arrives with high fever, especially if they are unvaccinated. While vaccinated children are much less likely to get measles, it’s still possible, especially in an environment with several cases of the virus. Recent international travel or living in or visiting a domestic area where measles is circulating should also sound warning bells for consideration of measles.
Measles is a nationally notifiable disease, so if you suspect the disease, contact your local public health department. They can assist with determining whether testing is warranted and provide information regarding what resources are available locally. Likewise, once a case of measles has been identified in their jurisdiction, they begin the work of limiting the spread in the community by working with the family, healthcare providers in the area, and the media to determine and communicate potential exposures.
Although you would likely be working with the health department, a few notes related to testing are worth mentioning:
- A nasopharyngeal (NP) PCR test is the primary and preferred diagnostic as it is more sensitive than urine, particularly early in illness.
- Urine PCR tests can be useful in prolonged cases or when NP swabs are not available.
- An IgM blood test is useful 3-5 days after rash onset. A positive IgM result in an unvaccinated person is highly suggestive of a recent measles infection.
- Because IgG levels will rise in blood samples 7-10 days after rash onset, this test is less useful for immediate diagnosis but can be helpful for confirming immunity.
- Because not all labs offer all tests, public health officials can be helpful in advising which local resources are available to establish a diagnosis of measles.
Treatment & management of measles
Supportive care for measles includes adequate hydration and fever management. Vitamin A supplementation is recommended for all children with measles. Prescribed doses range from 50,000 to 200,000 international units (IU) based on age. Because measles is so contagious, having patients recover at home is preferred over admission to a healthcare facility or hospital. However, complication rates are high, and children should be referred to a hospital if they develop:
- Signs of pneumonia, the most common cause of measles-related death
- Encephalitis, which occurs in approximately 1 in 1,000 cases
- Severe diarrhea and dehydration
Of every 1,000 children infected, one will die.
Long-term impact
Measles has health impacts beyond the immediate infection. For example, after a measles infection, people are at increased risk for other infections, including some they previously had immunity against, due to immune amnesia. Essentially, the measles virus attacks and kills some immune memory cells, depleting pre-existing immunity to infections like influenza and pneumococcus. As a result, the person is at increased risk for infections they were previously protected against. This increased susceptibility can last for 2-3 years.
Another rare but scary outcome of measles infection is known as subacute sclerosing panencephalitis (SSPE). SSPE is thought to result when measles virus infects cells of the brain, causing a long-term, undetectable, infection. Years later (on average 2-10 years), symptoms begin to appear in the form of decreases in school performance or increases in sleeplessness, forgetfulness or distractibility before worsening to outbursts, hallucinations, seizures and loss of intellect and speech. The disease is fatal and has no treatment. Children infected with measles virus before 2 years of age are at increased risk for this complication, which is more common in males but can occur in females as well.
Check out the VEC’s Parents PACK website for two families’ experiences with SSPE.
Infection control: Reducing the spread of measles
Measles is feared not just because of the severity of the illness but also its contagiousness. If a person with measles encounters a group of 10 susceptible people, most — if not all 10 — will get infected.
Because measles virus can hang in the air for up to two hours after an infected person leaves, the virus can easily spread in the community. It also spreads quickly in healthcare environments. For this reason, healthcare providers will want to be prepared for the possibility that an infected individual arrives at their facility:
Protecting patients
Anytime measles is being considered as a diagnosis, the patient should be immediately isolated. Ideally, if a family calls for an appointment and describes symptoms concerning for measles, plans should be made for the patient to arrive masked and not enter through the common waiting room. This protects other patients in the office, especially infants too young to have yet received the measles vaccine.
If available, patients suspected of having measles should be placed in an airborne isolation room, which is a room that has unique air handling, so air is directly removed from the healthcare facility. If such a room is unavailable, a standard room can be used with the door shut, keeping in mind that after that patient leaves, no other patients should be placed in that room for at least two hours.
Protecting staff
Healthcare workers should have documented immunity to measles and should use personal protective equipment, including an N95 mask.
Post-exposure measures
If susceptible individuals are exposed to measles, they should either receive MMR vaccine within 72 hours of the exposure or immune globulin within 6 days, depending on their medical history. As there are nuances related to their medical history (prior vaccination status, age, and time from exposure), consult your local public health officials or a detailed resource, such as this one from the New York City Health Department, when determining the best option for your patient. Following either vaccine or immune globulin, they should still isolate to monitor for symptoms. As a reminder, both unvaccinated and immune-compromised individuals can be considered susceptible.
Measles: Key clinical takeaways
As rates of measles vaccination fall below 95%, we are likely to see sporadic cases of measles, which can quickly lead to outbreaks. Prompt recognition by individual healthcare providers is critical as is partnership with local public health authorities. Not only can this ensure quick diagnosis and guidance for the family, but it can also ensure early intervention by public health officials to prevent further spread in the community.
Resources
- Measles: What You Should Know (Q&A)
- MMR (Infographic)
- Is the MMR Vaccine Safe? (video)
- Do I need a measles vaccine booster during an outbreak? (video)
- Doctors Talk: Measles (video)
- Vaccines on the Go: What You Should Know (mobile app)
- Rashes: What You Should Know (booklet)
Contributed by: Lori Handy, MD, MSCE , Charlotte A. Moser, MS, Paul A. Offit, MD
If vaccination rates continue to fall in the United States, vaccine-preventable diseases will become more prevalent. Many vaccine-preventable diseases may be unfamiliar to healthcare providers and families. To prepare for the more frequent appearance of diseases that are now uncommon, over the next few months, the Vaccine Update feature article will review key reminders about specific vaccine-preventable diseases for healthcare providers and include resources available for sharing with families.
The February article will focus on measles. Measles is a highly contagious respiratory virus. It is so contagious that someone can be infected simply by occupying the space an infected person was in two hours earlier. As described by VEC Director, Dr. Paul Offit, “… very, very tiny droplets … hang in the air like a ghost …”
Before the vaccine was introduced in 1963, virtually everyone was infected by 15 years of age. The virus sickened 3 million to 4 million people in the U.S. each year, but with the introduction of the vaccine, measles was eliminated by 2000. Unfortunately, this elimination status remains tenuous. In 2024, the U.S. had 285 cases of measles and 16 outbreaks. This compared to 59 cases and four outbreaks in 2023. By the second week of February 2025, the U.S. has had two outbreaks and at least 61 cases as reported by state and local health departments.
While two doses of measles vaccine are protective (97% effectiveness), as soon as population vaccination rates drop below 95%, cases and outbreaks increase.
Recognizing measles
Patients with measles initially have symptoms that look like many upper respiratory infections. The most classic description is a high fever (104°F or 40°C) and the “three Cs”: cough, coryza (runny nose), and conjunctivitis (red, watery eyes). Another symptom that can occur is the development of Koplik spots, which are tiny, white “grains of sand” inside the mouth, particularly inside the cheeks and lips. Koplik spots typically appear 1–2 days before the body rash; however, while these spots are well described, they are rare, so their absence does not help rule out measles. The classic body rash appears 2-4 days after these initial symptoms. The period before development of the body rash is when virus in the bloodstream is at its peak. By the time the rash appears, an immune response is developing, and quantities of virus in the blood are declining. This presence of virus prior to and after rash development explains the defined transmission period of four days before to four days after appearance of the rash. Notably, the rash begins at the hairline and spreads downward. Once described by a senior clinician as “a bucket of rash” poured over a child’s head, this pattern of appearance can help with diagnosis. A classic measles rash has a mix of flat and raised red lesions. The rash tends to fade in the same order it appeared. Symptoms typically resolve over the period of about a week.
Making a measles diagnosis
Because measles starts off like many other infections, clinicians need to maintain a high level of suspicion. One of the first moments to consider measles is if a child arrives with high fever, especially if they are unvaccinated. While vaccinated children are much less likely to get measles, it’s still possible, especially in an environment with several cases of the virus. Recent international travel or living in or visiting a domestic area where measles is circulating should also sound warning bells for consideration of measles.
Measles is a nationally notifiable disease, so if you suspect the disease, contact your local public health department. They can assist with determining whether testing is warranted and provide information regarding what resources are available locally. Likewise, once a case of measles has been identified in their jurisdiction, they begin the work of limiting the spread in the community by working with the family, healthcare providers in the area, and the media to determine and communicate potential exposures.
Although you would likely be working with the health department, a few notes related to testing are worth mentioning:
- A nasopharyngeal (NP) PCR test is the primary and preferred diagnostic as it is more sensitive than urine, particularly early in illness.
- Urine PCR tests can be useful in prolonged cases or when NP swabs are not available.
- An IgM blood test is useful 3-5 days after rash onset. A positive IgM result in an unvaccinated person is highly suggestive of a recent measles infection.
- Because IgG levels will rise in blood samples 7-10 days after rash onset, this test is less useful for immediate diagnosis but can be helpful for confirming immunity.
- Because not all labs offer all tests, public health officials can be helpful in advising which local resources are available to establish a diagnosis of measles.
Treatment & management of measles
Supportive care for measles includes adequate hydration and fever management. Vitamin A supplementation is recommended for all children with measles. Prescribed doses range from 50,000 to 200,000 international units (IU) based on age. Because measles is so contagious, having patients recover at home is preferred over admission to a healthcare facility or hospital. However, complication rates are high, and children should be referred to a hospital if they develop:
- Signs of pneumonia, the most common cause of measles-related death
- Encephalitis, which occurs in approximately 1 in 1,000 cases
- Severe diarrhea and dehydration
Of every 1,000 children infected, one will die.
Long-term impact
Measles has health impacts beyond the immediate infection. For example, after a measles infection, people are at increased risk for other infections, including some they previously had immunity against, due to immune amnesia. Essentially, the measles virus attacks and kills some immune memory cells, depleting pre-existing immunity to infections like influenza and pneumococcus. As a result, the person is at increased risk for infections they were previously protected against. This increased susceptibility can last for 2-3 years.
Another rare but scary outcome of measles infection is known as subacute sclerosing panencephalitis (SSPE). SSPE is thought to result when measles virus infects cells of the brain, causing a long-term, undetectable, infection. Years later (on average 2-10 years), symptoms begin to appear in the form of decreases in school performance or increases in sleeplessness, forgetfulness or distractibility before worsening to outbursts, hallucinations, seizures and loss of intellect and speech. The disease is fatal and has no treatment. Children infected with measles virus before 2 years of age are at increased risk for this complication, which is more common in males but can occur in females as well.
Check out the VEC’s Parents PACK website for two families’ experiences with SSPE.
Infection control: Reducing the spread of measles
Measles is feared not just because of the severity of the illness but also its contagiousness. If a person with measles encounters a group of 10 susceptible people, most — if not all 10 — will get infected.
Because measles virus can hang in the air for up to two hours after an infected person leaves, the virus can easily spread in the community. It also spreads quickly in healthcare environments. For this reason, healthcare providers will want to be prepared for the possibility that an infected individual arrives at their facility:
Protecting patients
Anytime measles is being considered as a diagnosis, the patient should be immediately isolated. Ideally, if a family calls for an appointment and describes symptoms concerning for measles, plans should be made for the patient to arrive masked and not enter through the common waiting room. This protects other patients in the office, especially infants too young to have yet received the measles vaccine.
If available, patients suspected of having measles should be placed in an airborne isolation room, which is a room that has unique air handling, so air is directly removed from the healthcare facility. If such a room is unavailable, a standard room can be used with the door shut, keeping in mind that after that patient leaves, no other patients should be placed in that room for at least two hours.
Protecting staff
Healthcare workers should have documented immunity to measles and should use personal protective equipment, including an N95 mask.
Post-exposure measures
If susceptible individuals are exposed to measles, they should either receive MMR vaccine within 72 hours of the exposure or immune globulin within 6 days, depending on their medical history. As there are nuances related to their medical history (prior vaccination status, age, and time from exposure), consult your local public health officials or a detailed resource, such as this one from the New York City Health Department, when determining the best option for your patient. Following either vaccine or immune globulin, they should still isolate to monitor for symptoms. As a reminder, both unvaccinated and immune-compromised individuals can be considered susceptible.
Measles: Key clinical takeaways
As rates of measles vaccination fall below 95%, we are likely to see sporadic cases of measles, which can quickly lead to outbreaks. Prompt recognition by individual healthcare providers is critical as is partnership with local public health authorities. Not only can this ensure quick diagnosis and guidance for the family, but it can also ensure early intervention by public health officials to prevent further spread in the community.
Resources
- Measles: What You Should Know (Q&A)
- MMR (Infographic)
- Is the MMR Vaccine Safe? (video)
- Do I need a measles vaccine booster during an outbreak? (video)
- Doctors Talk: Measles (video)
- Vaccines on the Go: What You Should Know (mobile app)
- Rashes: What You Should Know (booklet)
Contributed by: Lori Handy, MD, MSCE , Charlotte A. Moser, MS, Paul A. Offit, MD