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Measles Resurgence in 2024: What You Need to Know

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On Behalf of the Emerging Infectious Disease Taskforce

Measles is having a resurgence in the United States. The CDC has documented 139 measles cases as of May 16, 2024. This is almost two and a half times the total number of cases reported for the entire year of 2023. There have been a record 10 outbreaks of measles in the United States so far this year. The majority of reported measles cases thus far are associated with these outbreaks.

What is Measles?

Measles is a dangerous paramyxovirus infection presenting with a high fever – around 105°F (40.55°C) and the triad of cough, coryza, and conjunctivitis. This is accompanied by a maculopapular red rash starting on the face before spreading to the trunk and extremities.

The Contagious Nature of Measles

Measles is one of the most contagious viral diseases known with an estimated Basic Reproductive Number (Ro) from 14 to 18. A Ro of 14 to 18 means that a single case of measles in an unprotected population can cause 14 to 18 new cases of the disease. The virus is spread by contact, droplet, and aerosol mechanisms. Vaccines and public health measures are highly effective in preventing measles.

Effectiveness of Measles Vaccines

A safe and effective vaccine for measles is FDA-licensed, approved, and available. After being introduced in 1963, vaccines dramatically dropped global measles death rates from four million yearly to about 100,000 currently. Before the measles vaccines, the United States had 500 deaths, 50,000 hospitalizations, and 1,000 encephalitis cases yearly. Since the vaccine, the United States has seen a 99% reduction of measles cases. The last death from measles in the United States was reported in 2015. More basic information on the measles vaccine is found in the references and resources of this post.

Measles Prevention is Essential

As noted before, measles is not a benign childhood disease. Although death is rare in economically developed nations, the disease is capable of producing serious long-term effects. The primary complications of measles include:

  • Pneumonia (primary measles pneumonia and secondary bacterial pneumonia)
  • Laryngotracheobronchitis (LTB)
  • Otitis Media
  • Encephalitis
  • Subacute Sclerosing Panencephalitis (SSPE)

Subacute sclerosing panencephalitis (SSPE) is a progressive degenerative CNS disorder in children and young adults. It is a persistent viral infection related to measles resulting in devastating neurological deficits. More information on SSPE and other impacts of measles is provided in the references for this post.

An Eradicated Disease?

Measles was declared eradicated from the United States as an endemic disease in 2000. This was based on the fact that the virus had not been continuously transmitted in the U.S. population for the previous six years. Only sporadic outbreaks of measles have been seen since that time.

Unfortunately, a consistently increasing number of outbreaks – defined as three or more related measles cases – are now being seen in the United States. Since 2020, there have been 20 measles outbreaks in the United States. A total of 10 (50%) of these outbreaks happened in the first five months of 2024. This trend of increasing outbreaks threatens to return measles to an endemic disease in this country.

Why is Measles Increasing in the United States?

Measles is a vaccine-preventable disease. Despite unsupported opinions to the contrary, the available measles vaccine in the United States is safe and effective. Vaccine hesitancy and vaccine non-compliance are the primary reason measles is on the increase.

Along with its socioeconomic and political impacts, the pandemic also caused parents and caregivers to forego the vaccination of adults and children in some communities. This has been exacerbated by a failure of public health professionals to adequately educate both the community and political leaders regarding the proven positive impacts of vaccinations. Each of us should make efforts to educate our patients regarding the safety and effectiveness of vaccines during each patient encounter. This should include documenting, considering, and counseling when needed the patient or caregiver regarding that immunization history.

Vaccine-preventable diseases represent a clear and present danger to the lives and well-being of children and adults. Clinicians should educate and promote appropriate vaccination practices to policy-makers and their communities.

Pockets of Risk

All these root causes for vaccine hesitancy result in pockets of unvaccinated individuals within larger communities. Such concentrated pockets of unvaccinated individuals eliminate the protection of primary vaccination and negate any herd immunity effects within that pocket population. The higher number of cases developing in the unvaccinated pocket population then places susceptible individuals in the larger surrounding community at risk for that disease.

Measles Vaccine Threshold Levels

To keep measles under control, population vaccination compliance needs to be close to 95%. In recent years, pediatric vaccination rates in many states have dropped to 90% or less for all childhood immunizations. This includes declining vaccination rates for several diseases including measles, mumps, rubella and even polio. At the same time, the risk of importation of all diseases into the United States is increasing.

Closing Points

Vaccine-preventable diseases – particularly measles, are making a comeback in the United States. The impacts of the social and economic forces of the pandemic coupled with a general decline of public health support by many political decision-makers have helped promote a decline in vaccination compliance rates. These influences have resulted in vaccine compliance for measles dropping below the 95% level needed to prevent the disease from becoming endemic in the United States once again.

Clinicians need to be vigilant for cases of measles seen in the clinic and emergency department. These patients need to be isolated when measles is suspected. Management depends on the severity of the illness. Pediatric (for children) and infectious disease consultation should be obtained. Public health professionals should be consulted for reporting and assistance with community health impacts. All healthcare providers need to be vaccinated against measles.

Education of healthcare providers, parents and political decision-makers is paramount in decreasing vaccine hesitancy and protecting our communities.

Learn more about TeamHealth’s Emerging Infectious Disease Taskforce (EIDT) and see a full list of references