Measles 101

Introduction

Measles was once a potentially life-threatening disease prior to the introduction of preventive vaccines. Subsequent to the advent of vaccinations, this highly contagious disease was thought to be eradicated in the United States by 2000 [1,2]. Now, there is a new measles epidemic. As of 5 September 2019, the Centers for Disease Control and Prevention reported 1241 cases of measles since the beginning of 2019 [3]. This is the highest number documented in a single year since 1994, when 963 cases occurred [3]. Being clinically up-to-date about measles should be helpful, especially for American physicians who completed their training and/or practiced only in recent years.

Vaccine

The first measles vaccine was licensed in 1963. The measles-mumps-rubella (MMR) vaccine was licensed for use in 1971. Since then there was dramatic decline in the number of reported cases of measles in this country.

Anti-vaxxers

There are many people who refuse vaccinations for their children and/or themselves. This seems often to be based on an erroneous belief that the MMR vaccine causes autism [4]. Some others have religious or philosophical views that support vaccine refusal [5]. For example, objections are sometimes because of the use of aborted fetal tissue in the rubella component of the combined vaccine and the animal-derived gelatins are utilized in its production.

Pathophysiology

Measles is a single-stranded RNA virus of the Paramyxoviridae family. A highly infectious disease, measles is transmitted by aerosol-borne respiratory droplets [6]. This allows viruses to enter the body and infect dendritic cells in the alveoli [7]. These drain into lymph nodes and involve lymphocytes, leading to viral replication. Infected cells circulate in the blood and spread throughout the body, delivering viruses to the skin, lung, liver, spleen, and brain [6].

Clinical

The incubation period is between 6 and 19 days. Based on the duration, signs, and symptoms, measles is divided into two stages: a prodrome and an exanthematous phase.

The prodromal phase appears approximately 10–12 days after incubation [8]. Fever increases in step-wise fashion up to 104°F, or higher. The prodrome also includes cough, tracheobronchitis, conjunctivitis, rhinitis, and coryza [8,9]. Koplik spots occur and are a pathognomonic sign. They are a cluster of bluish-white areas on the buccal mucosa, at the second molar [10–12]. The whitish portion is likely due to the destruction of glandular epithelial cells and the bluish-red halo around it is caused by vasodilation near the duct of the submucosal gland. In some persons of darker skin color, Koplik spots often appear more as depigmented areas. As the rash on the skin progresses, Koplik spots disappear and buccal mucous membrane return to their baseline [10,11].

The exanthematous phase is evident approximately 14 days after exposure and lasts for 2–4 days [12]. It initially includes macules and papules on the face and behind the ears, spreading to the neck and then to the torso and extremities. Later, these cutaneous eruptions become confluent. The rash may even desquamate and fades in the same order as it emerged [13].

Differentials

There are other causes of fever and maculopapular eruptions. These include rubella, parvovirus B19, enterovirus, scarlet fever, human herpesvirus 6 and 7, Kawasaki disease, meningococcemia, toxic shock syndrome, dengue, human immunodeficiency virus (HIV 1 and 2), secondary syphilis, and drug eruptions [14].

Diagnosis

The clinical diagnosis of measles usually requires a three-day history of fever, with at least one of the following: cough, coryza, or conjunctivitis. Koplik spots are also diagnostic. Measles should be considered in the differential of any erythematous rash with fever in a child [15].

Diagnosis can also be confirmed by serological tests, cultures, and viral isolation or genome detection by real-time polymerase chain reactions (RT-PCR). The IgM enzyme-linked immunosorbent assay has sensitivity of over 80% and specificity about 95% from samples collected 3–28 days after the appearance of the rash. Newer immunoassays document better sensitivity. Cultures of blood, urine, conjunctival swabs, and respiratory secretions can provide diagnostic assistance [16].

Complications

About 30–40% of patients with measles develop complications [17]. These are usually more severe in young children, geriatric patients, and malnourished individuals.

The leading cause of measles-associated death is respiratory tract involvement, including pneumonia [17]. Other complications include otitis media, stomatitis, diarrhea, and keratoconjunctivitis [12,17,18]. Measles can induce premature delivery, spontaneous abortions, and/or serious neonatal infections [17–19].

Measles also causes severe neurologic complications including seizures, primary measles encephalitis, acute post-infectious encephalomyelitis, and subacute sclerosing panencephalitis [18].

Treatment

There is no specific antiviral treatment for measles. Management involves supportive care by managing fever and hydration, identification and treatment of complications, and preventing the spread of disease by precautions against infection. Patients and/or caregiver illness-education is stressed [17,19].

Oral vitamin A is prescribed for children. The dose for those under 6 months of age is 50,000 IU on two consecutive days, for those from 6 to 12 months prescribe 100,000 IU on two consecutive days, and for older children administer 200,000 IU over two consecutive days [20]. Dosing is repeated in 4 weeks whenever there is evidence of vitamin A deficiency [20].

Discussion

A better understanding of measles pathophysiology and other findings would improve clinical diagnostic precision. High levels of population immunity should be sustained to prevent a resurgence of measles. To counter anti-vaccination fears, measles disease-burden should be addressed, especially regarding its life-threatening potential. Always encourage up-to-date vaccine administrations and answer any questions or concerns about immunizations. When most of the population is measles protected, the whole society is safer from what is termed ‘herd immunity’.

Declaration of financial/other relationships

Authors and peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Declaration of interest

No potential conflict of interest was reported by the authors.

Acknowledgments

None reported.

Additional information

Funding

This paper was not funded.