Francisco R. Velázquez: Measles in 2023 are eliminated, but not eradicated

By Francisco R. Velázquez, M.D., S.M., FCAP

Measles was declared eliminated in the United States in 2000 and in the Americas by 2015. But elimination does not mean eradication, and outbreaks continue to occur not only here, but globally.

Outbreaks can happen anywhere that people are either unvaccinated or under vaccinated.

Recently, a confirmed case of measles in an adult female was reported in King County. The patient is unvaccinated and has a recent history of international travel. Therefore, the infection was most likely acquired outside of the U.S. This is the second documented case in the U.S. in 2023.

For historical context, let’s take a look at the 2022 outbreak in Ohio where 85 patients younger than 18 were affected. The Ohio outbreak made up the bulk of the United States’ 121 cases reported that year in six jurisdictions. Prior to that, the most significant outbreak took place in 2019 when 1,274 individuals from 31 different states were confirmed to be infected. That year, we had two outbreaks in Washington and one isolated case for a total of 87 cases.

The measles virus, also known as rubeola, is an enveloped RNA virus that has been around since the 11th or 12th century. It causes an acute, highly contagious infection usually seen in children. Recovery from the infection is common, but severe complications can occur, particularly in those with impaired cellular immunity due to disease, therapies or severe malnutrition. Some of the complications can be severe diarrhea, ear infections, blindness, pneumonia and encephalitis. Pneumonia is the most common severe complication and accounts for most measles-associated deaths.

At the global level, measles continues to be a leading cause of death among young children despite the availability of a safe and effective vaccine. There is no specific antiviral treatment against the measles virus although several therapies have been utilized over the years. Worldwide, it is estimated that the frequency of cases is roughly 36 cases per 1 million in population, with more than 130,000 deaths. Mortality in children is estimated to be between 1 and 2 for every 1,000 children infected. The frequency of pneumonias as a complication can be as high as 1 out of every 20, and for encephalitis – one out of every 1,000. The latter can cause lifelong consequences, such as seizures, deafness or intellectual disabilities.

Before widespread vaccination began in the 1980s, measles caused 2.6 million deaths a year with 12,000 of those in the Americas. The World Health Organization estimates that measles vaccination prevented 17.1 million deaths between 2000 and 2014. Research suggests that without a vaccine, an epidemic of measles lasting three to four months could occur every two to five years in late winter and early spring depending on the geographical location.

Measles is seen in every country in the world, and humans are the only natural host for the natural, unchanged form of the virus. Occasionally, monkeys can also get infected. Measles is transmitted from person to person by respiratory droplets over short distances, but also by small particle aerosols that can remain suspended in the air for several hours. A single infected individual can infect as many as 18 other people.

Once infected, the incubation period is 10 to 14 days before the typical rash appears. During this time, the peak of viremia (when the virus enters the blood) coincides with the prodromal phase (before the typical symptoms appear). Once the incubation period has passed, a fever will appear accompanied by cough, coryza (runny nose, congestion and possible loss of smell) and conjunctivitis. Koplik spots (slightly raised, bluish-white lesions on a reddened base) usually appear one day before the typical rash and last for two to three days. The skin rash will last for three to seven days, and its clearing could indicate the end of the infection. However, intense desquamation (skin is scaly and peeling) can follow in severely malnourished children. Most patients will be infectious one to two days before the onset of fever, and three to five days before the onset of the rash.

Given its global presence, measles can enter the U.S. through travel to or from areas in which the disease is present. There are various types of vaccines around the world. The combined mumps, measles, rubella (MMR) vaccine is the most commonly administered in Europe and North America. A quadrivalent vaccine which includes varicella (MMRV) is also available. The recommended two-dose vaccination is highly effective, but evidence suggest that vaccination coverage (herd immunity) needs to be at roughly 95% to prevent outbreaks.

According to the Centers for Disease Control and Prevention, about 90% of children younger than 2, and 92% of those between 13 to 17 years of age have received the MMR vaccine. At the end of last year, the WHO and CDC issued a report stating that roughly 40 million children were at risk globally because during 2021, 25 million children missed the first dose and almost 15 million missed the second dose. In Spokane County, the Washington state Department of Health’s most recent data (2021) shows that only 75% of children ages 19 to 35 months received their first MMR dose, and only 62% of children ages 4 to 6 completed the two-dose series.

Lower vaccination rates leave our community at greater risk of a measles outbreak, but we have an opportunity to mitigate the risk. Vaccines, contact tracing and appropriate quarantine are effective tools against the spread of measles. Talk to your provider about appropriate coverage for you and your family.

Francisco R. Velázquez, M.D., S.M., FCAP, is health officer of the Spokane Regional Health District.