EMS Primer: Understanding Measles: A Guide for EMS Clinicians

During the recent measles outbreak in Texas, the fact that there has been a second death has drawn attention to the fact that childhood illnesses are not benign.¹ Measles is a highly contagious viral disease and poses significant public health challenges, especially during outbreaks. For EMS professionals, understanding the epidemiology, transmission, clinical manifestations, and prevention strategies of measles is essential, not only to protect themselves and their patients, but also to play a pivotal role in preventing further spread in the community. Despite measles being declared eliminated in the United States in 2000, recent years have seen a resurgence of measles cases, largely due to international travel and declining vaccination rates.² Let’s focus on a comprehensive overview of measles, concentrating on transmission, prevention, and the EMS provider's role in early identification and containment.

Etiology and Epidemiology

Measles is caused by the virus measles morbillivirus, a member of the Paramyxoviridae family. It is one of the most contagious infectious diseases, with a basic reproduction number (R₀) between 12 and 18, meaning one infected person can transmit the virus to up to 18 susceptible individuals in a fully susceptible population.^3–5

In 2024, measles outbreaks were reported in several U.S. states, often linked to unvaccinated international travelers or communities with low vaccination coverage.² These outbreaks underscore the importance of vaccination and early recognition in high-risk populations.

Complications

The most common complications associated with measles exposure are ear infections and diarrhea. One in five unvaccinated people in the U.S. who get measles is hospitalized and as many as one out of every 20 children with measles gets pneumonia, the most common cause of death from measles in young children. Encephalitis (swelling of the brain) will develop in one child out of every 1,000 who get measles, which can lead to convulsions and leave the child deaf or with intellectual disability. As we have seen in Texasm, nearly one to three of every 1,000 children who become infected with measles will die from respiratory and neurologic complications.^3-6

Modes of Transmission

Measles is primarily transmitted via respiratory droplets and airborne spread. Infected individuals can transmit the virus by coughing, sneezing, or simply breathing near others. The virus can remain viable in the air or on surfaces for up to two hours after an infected person has left an area.⁶ Transmission can occur before the onset of the characteristic rash, specifically from four days before to four days after rash onset, making presymptomatic carriers a significant concern.

EMS personnel are particularly at risk during patient encounters in enclosed spaces such as ambulances, which can facilitate airborne transmission. If we administer oxygen to a patient, that will further increase the chances of exposure. Additionally, because the early symptoms of measles mimic other viral illnesses, the disease may not be initially suspected, increasing the potential for unprotected exposure.

Clinical Presentation

Understanding the clinical stages of measles can aid EMS professionals in early identification. Measles progresses through the following stages:^3-5

1. Incubation Period: Lasts 10–12 days post-exposure. Patients are asymptomatic but contagious near the end of this phase.
2. Prodrome: Characterized by high fever (up to 104°F), cough, coryza (runny nose), and conjunctivitis, the “three Cs.” This stage typically lasts two to four days.
3. Enanthem: Koplik spots, small white lesions with red halos on the buccal mucosa, may appear one to two days before the rash and are pathognomonic for measles.
4. Exanthem: A maculopapular rash begins on the face and spreads cephalocaudally (from head to toe). It typically lasts five to six days and fades in the same order.
5. Recovery: Symptoms subside gradually, although complications can arise during or after the illness.

Complications such as pneumonia, otitis media, encephalitis, and subacute sclerosing panencephalitis (SSPE) are more common in young children, immunocompromised individuals, and pregnant women.⁸

Diagnosis in the Field

While EMS providers are not responsible for diagnosing measles, maintaining a high index of suspicion is crucial during outbreaks or in cases involving unvaccinated individuals with fever, rash, and upper respiratory symptoms. A focused history should include:

• Vaccination status
• Travel history or exposure to international travelers
• Known travel to an area where there is a current outbreak
• Known outbreaks in the community
• Contact with anyone exhibiting a rash illness

Infection Control and Prevention in the EMS Environment

Given the airborne nature of measles transmission, strict infection control practices are essential. The following are best practices for EMS professionals:

1. Vaccination

The most effective prevention strategy against measles is vaccination with the measles, mumps, and rubella (MMR) vaccine. The CDC recommends that all healthcare workers, including EMS personnel, have documented evidence of immunity, defined as:

• Two doses of MMR vaccine, or
• Laboratory evidence of immunity or prior infection

Unvaccinated or incompletely vaccinated EMS personnel are at high risk of both contracting and transmitting the virus.⁷

2. Use of Personal Protective Equipment (PPE)

During suspected measles cases, EMS professionals should:

• Have a high degree of suspicion for any and all patients, especially patients with fever or rash or respiratory complaints
• Wear a properly fitted N95 respirator or higher-level respiratory protection
• Use gloves and eye protection if in close contact
• Provide an N95 surgical mask to the patient, if tolerated
• If you transport any family or friends with the patient, they should wear a mask as well. They may be in that incubation period where they are asymptomatic.

Proper donning and doffing techniques are vital to prevent contamination. Remember that a patient with a high viral load (the amount of virus in their body) will deliver a much higher viral dose to the people they infect. Masks are key to reducing viral exposure as they reduce the amount of viral dose you will be exposed to.

3. Scene and Transport Management

When transporting suspected measles patients:

• Minimize personnel exposure; only essential staff should be in the ambulance.
• Ventilate the patient compartment by using exhaust fans, air-conditioning, and opening windows if possible.
• Notify the receiving hospital of a suspected case before arrival.
• Wait outside the emergency department for direction where you will be placing your patient, then proceed directly to the room.
• Thoroughly disinfect the vehicle and equipment after transport using EPA-registered disinfectants.

Isolation precautions should be maintained during handoff until the patient is placed in an airborne infection isolation room (AIIR).

When treating suspected measles patients:^4-5

• Assess and re-assess. If your patient has waited a considerably long period of time before seeking treatment, their condition may serious or in danger of decompensating. Patients don’t suddenly crash; we suddenly notice.
• Airway, breathing, and oxygen administration are key.
• Venous access and fluids for patients who are dehydrated or in extremis.

Post-Exposure Protocols

If an EMS provider is exposed to a measles case and lacks evidence of immunity, post-exposure prophylaxis (PEP) with the MMR vaccine within 72 hours or immune globulin within six days may be indicated.⁷ Affected personnel may be excluded from work from the fifth to 21st day after exposure, depending on vaccination status and immune response.

EMS agencies should have protocols for:

• Prompt exposure reporting
• Contact tracing
• Post-exposure evaluation and work restrictions

Role of EMS in Public Health Surveillance

EMS professionals are often the first point of medical contact for contagious patients and play a critical role in public health surveillance. During measles outbreaks, accurate documentation and communication with public health departments can facilitate early identification, and isolation, reducing secondary transmission.

Key documentation elements include:

• Onset and progression of symptoms
• Rash description and location
• Runny nose
• Vaccination and exposure history
• Names and contact information of exposed individuals

Communication and Patient Education

EMS personnel can also help mitigate the spread of measles through public education. While in the field, opportunities may arise to:

• Encourage vaccination in unvaccinated individuals
• Explain symptoms and the importance of isolation
• Reinforce the need for medical follow-up in suspected cases

Given the increase in vaccine hesitancy, EMS professionals must communicate with empathy, providing factual and nonjudgmental information.

Organizational Preparedness

EMS agencies should proactively prepare for measles outbreaks by:

• Verifying staff immunity
• Stocking PPE and respiratory protection
• Training on airborne precautions and infection control
• Collaborating with local health departments and hospitals

A coordinated response minimizes risk to personnel and supports broader public health containment efforts. If you are not having monthly meetings with your public health department, now is a good time to begin them. They are vital resource for any EMS agency.

The National Emerging Special Pathogens Training and Education Center (NETEC) is a fantastic resource for all EMS providers. They provide free training and educational resources geared toward EMS agencies and healthcare systems. They should be the first stop for any EMS agency looking to train their staff or access the latest information regarding infectious diseases.

Conclusion

Measles remains a serious public health threat, and EMS professionals are on the front lines of response and containment. By understanding the transmission dynamics, recognizing early signs and symptoms, implementing appropriate infection control measures, and ensuring personal immunity through vaccination, EMS providers can safeguard their own health and that of the public. With increased vigilance and preparedness, the EMS community can play a vital role in controlling measles outbreaks and promoting community health resilience.

References

1. Texas Department of Health and Human Services, https://www.dshs.texas.gov/news-alerts/texas-announces-second-death-measles-outbreak
2. Centers for Disease Control and Prevention. (2024). Measles cases and outbreaks. https://www.cdc.gov/measles/cases-outbreaks.html
3. Paules, C. I., Marston, H. D., & Fauci, A. S. (2019). Measles in 2019 ,  Going backward. New England Journal of Medicine, 380(23), 2185–2187. https://doi.org/10.1056/NEJMp1905099
4. AMLS: Advanced Medical Life Support: Advanced Medical Life Support 3rd Edition by National Association of Emergency Medical Technicians (NAEMT), Jones and Bartlett, 2021
5. Chapleau, W., Burba, A., Pons, P. M., & Page, D. (2011). The Paramedic Updated Edition (1st ed.). McGraw-Hill Education
6. Centers for Disease Control and Prevention. (2023). Measles (Rubeola): Transmission. https://www.cdc.gov/measles/signs-symptoms/index.html
7. Centers for Disease Control and Prevention. (2025). Advisory Committee on Immunization Practices (ACIP). https://www.cdc.gov/acip/vaccine-recommendations/index.html
8. World Health Organization. (2023). Measles. https://www.who.int/news-room/fact-sheets/detail/measles