US Measles Cases Keep Increasing, Highest in 25 Years, CDC Says

Troy Brown, RN

April 29, 2019

The number of confirmed measles cases has grown to 704 in 22 states as of April 26, and Washington state has declared its measles outbreak over, according to information presented by the Centers for Disease Control and Prevention (CDC) at a media teleconference today.

The CDC held the teleconference to address the continuing outbreak of a vaccine-preventable disease, why it is happening, and what can be done to stop it.

"Vaccine-preventable diseases belong in the history books, not our emergency rooms," said Alex Azar, secretary, Department of Health and Human Services.

"The good news is that last night the Washington state department of health declared their outbreak over. However, the outbreaks in New York City and New York state are the largest and longest-lasting since measles elimination in 2000. The longer these outbreaks continue, the greater the chances that measles will again get a foothold in the United States," said Nancy Messonnier, MD, director, NCIRD, CDC.

The CDC continues to focus on increasing immunization, widely accepted as the best strategy for containing the disease. To that end, Azar announced that today marks the beginning of National Infant Immunization Week, which celebrates its 25th anniversary this year.

The CDC also reported on the latest measles cases in an article published April 29 in MMWR.

The number of measles cases is the highest it has been since 1994 when there were 963 cases, Manisha Patel, MD, Division of Viral Diseases, NCIRD, CDC, and colleagues write.

Among the 704 confirmed cases, 503 (71%) occurred in unvaccinated individuals and 689 (98%) were US residents. Most (88%) of the 704 cases occurred in close-knit communities.

Imported Cases Fueled Outbreaks

"The recent outbreaks started through what we call importation," Messonnier said. "Measles is imported when an unvaccinated traveler visits a country where there is widespread measles transmission, gets infected with measles, and returns to the United States. That traveler then exposes people in their community who are not vaccinated."

"Cases are considered to be internationally imported if at least part of the exposure period (7-21 days before rash onset) occurred outside the United States and rash occurred within 21 days of entry into the United States, with no known exposure to measles in the United States during the exposure period," Patel and colleagues explain.

Forty-four measles cases were directly imported from other countries. Of those, 34 (77%) occurred in US residents who traveled internationally and brought measles back with them. Forty (91%) of the imported cases occurred in unvaccinated individuals or those with unknown vaccination status. All 40 cases were in individuals old enough to receive the measles-mumps-rubella (MMR) vaccine.

The three countries responsible for the highest numbers of imported cases were the Philippines (14 cases), Ukraine (eight), and Israel (five), followed by Thailand (three), Vietnam (two), and Germany (two). One case was imported from each of the following countries: Algeria, France, India, Lithuania, Russia, and the United Kingdom.

Four individuals had traveled to multiple countries during their exposure period, including Italy/Singapore, Thailand/Cambodia, Ukraine/Israel, and Cambodia/Thailand/China/Singapore.

Of the imported cases, 23 did not result in any known secondary cases.

"High two-dose measles vaccination coverage in the United States has been critical to limiting transmission. However, increased global measles activity poses a risk to US elimination, particularly when unvaccinated travelers acquire measles abroad and return to communities with low vaccination rates," Patel and colleagues write.

Children aged 6 through 11 months who are traveling abroad with their families should get one dose of MMR vaccine before travel. Children aged 12 months or older need two doses separated by at least 28 days. Adolescents and adults who have not had measles or who have not been vaccinated should receive two doses separated by at least 28 days.

Those who are traveling internationally should try to be fully vaccinated at least 2 weeks before they travel; however, "even if your trip is less than 2 weeks away, you should still get a dose before you depart," Robert Redfield, MD, director, CDC, said.

CDC Renews Call for Vaccination

Of cases in 2019, 9% have been hospitalized and 3% have had pneumonia, Redfield said. Measles is incredibly contagious and an individual can spread it 4 days before developing a rash.

"If an infected person enters a room with 10 unvaccinated people, nine of them will get measles," Redfield explained.

"The majority of parents are making sure their children get vaccinated according to CDC's recommended immunization schedule," Redfield said. "Two doses of MMR vaccine are about 97% effective at preventing measles. One dose is about 93% effective. When you get vaccinated, you also protect others around you who are at high risk for complications but can't get vaccinated because they're too young or have a health condition," he explained.

The CDC recommends that children get two doses of MMR vaccine, with the first dose at age 12-15 months and the second dose at age 4-6 years. Older children and adults should be up-to-date with their immunizations.

When measles is imported into a community with high vaccination rates, outbreaks do not occur or are small. Once measles occurs in an undervaccinated community, it is difficult to control its spread, according to the CDC.

Misinformation about the vaccine is another reason the current outbreaks are occurring. "Sadly, these communities are being targeted with inaccurate and misleading information about vaccines," Messonnier said.

Measles can be very costly and disruptive to public health, she said; it can cost as much as $32,000 per case. "That does not capture cost from the community perspective and the cost to individuals and their families."

What CDC Is Doing

The CDC has implemented an "incident management structure" within the National Center for Immunization and Respiratory Diseases (NCIRD) to respond to the outbreak. They are reinforcing to healthcare providers the guidelines for recognition and prevention of measles. CDC has also developed a toolkit with resources pediatricians can use when talking to parents about vaccines.

CDC continues to reach out to rabbis and Jewish medical organizations to disseminate accurate information "through credible sources," Messonnier said, because some of the worst outbreaks are occurring in ultra-Orthodox Jewish communities.

"We have definitely seen myths and misinformation about vaccines being sent to susceptible communities; that is, communities susceptible to that misinformation," Messonnier said.

The reasons why those communities are chosen are unclear, she said, but "we definitely see that information targeted, and these vulnerable communities are the communities in which we're seeing these outbreaks right now."

It is also important to increase community vaccination numbers so that unvaccinated individuals will also be protected by herd immunity.

"The public health community, community organizers, and the rabbinical associations are all working together to correct misinformation and get folks vaccinated, and I think these outbreaks can end, with all of those groups working together. But I think we will see additional cases before this is over," Messonnier said.

Thirteen Outbreaks

Including the outbreak in Washington, there have been 13 outbreaks (663 cases; 94% of all cases) in the United States in 2019. Six of those were linked to underimmunized close-knit communities, accounting for 88% of reported cases.

Washington state had 72 confirmed cases; two individuals with measles moved from Washington to Georgia and the numbers from those two states have been revised accordingly.

In Rockland County, New York, there have been 202 cases as of April 29. In Brooklyn and Queens, New York City, there have been 390 cases as of April 24. In Michigan, there have been 43 cases as of April 17. In New Jersey, there have been 14 cases as of April 23.

In California, there have been 38 confirmed cases as of April 24. In Georgia, there have been six cases as of April 29. In Maryland, there have been four cases as of April 19. In Washington state, there have been 72 cases as of April 24.

The highest number of reported cases per week was 87 during the week ending March 23. The median age of patients was 5 years (interquartile range, 1-18.5 years); 25 (4%) cases were in infants aged < 6 months, 68 (10%) in infants aged 6-11 months, 76 (11%) in children aged 12-15 months, 167 (24%) in children aged 16 months - 4 years, 203 (29%) in children aged 5-19 years, 138 (20%) in adults aged 20-49 years, and 27 (4%) in adults aged 50 years or older.

There were no reports of death or cases of encephalitis.

Almost three quarters (503 cases; 71%) of patients with measles were unvaccinated; 76 (11%) were vaccinated (had received ≥ 1 dose of MMR vaccine), and 125 (18%) had unknown vaccination status.

"We know vaccines are safe because they are among some of the most studied medical products we have," Redfield said.

Patel and colleagues have disclosed no relevant financial relationships.

MMWR. Published online April 29, 2019. Full text

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