Rise in measles and other infectious diseases has U.S. public health experts on alert

A Swiss woman who had been traveling in Mexico arrived at a Tucson, Ariz., emergency room with symptoms that included a rash and difficulty breathing. Two days passed before she was diagnosed with measles and placed in isolation. By that time, she had transmitted the disease to another woman who was in the emergency department at the same time. That woman then passed the measles infection to a hospital staffer who had not been vaccinated, as well as to an 11-month-old child who was too young to get vaccinated.

In all, 14 confirmed cases and 363 suspected cases resulted from the Swiss traveler's case of measles. Of the confirmed cases, seven people got the disease while in the care of two hospitals for other medical conditions. A 2011 study in the Journal of Infectious Diseases calculated the cost of the hospitals' responses to the 2008 outbreak at more than $799,000.

That Arizona outbreak illustrates the potential costs associated with the recent rise in the number of cases of Americans diagnosed with infectious diseases that experts thought had been virtually eliminated in the U.S. This has prompted public health experts to examine new methods of addressing outbreaks of vaccine-preventable illnesses. And in the face of unfounded claims that vaccines cause autism and other disorders, public health authorities also are searching for better ways to convince Americans that the benefits of getting their children vaccinated far outweigh any risks.

Yearly vaccinations of the nation's schoolchildren have resulted in the elimination of or vast reduction in the number of reported cases of diseases including measles, pertussis, polio, mumps, diphtheria and rubella that once were responsible for killing hundreds of children annually. But cases of diseases such as measles and pertussis have been rising in recent years in areas of the country where child immunization rates have fallen below rates considered acceptable by public health authorities to maintain public safety against infection.

“We have seen more measles recently, and it has been attributed mainly to parents who aren't vaccinating their kids,” said Dr. Daniel Salmon, deputy director of the Institute for Vaccine Safety at Johns Hopkins University. “We have also seen more pertussis, and it's primarily been attributed to the waning of the vaccine.”

According to the Centers for Disease Control and Prevention, the growth in pertussis cases can be traced to the 1990s when the whole cell vaccine, or DTP, was replaced by the acellular pertussis vaccine, DTaP. It is believed the DTaP vaccine does not provide protection as long as the DTP vaccine does. In 2012, more than 48,000 pertussis cases were reported—the highest number since 1955.

As for measles, the disease was declared “eliminated” in the U.S. in 2000. But 911 cases have been reported between 2001 and 2011, according to the CDC. As of Nov. 2, there have been 161 measles cases reported across 16 states this year, the highest number of cases since 2011, when 220 were reported.

Experts say the spread of measles can be traced to people who contracted the disease outside the U.S. and brought it into this country. They in turn spread the disease to people who were not vaccinated.

Salmon said while the number of reported cases of measles and pertussis does not suggest a return to the nationwide outbreaks of those diseases that were seen before the widespread adoption of vaccines, the growing incidence could strain state and local public health systems, which have faced substantial budget cuts in recent years. “While I think generally the medical and public health systems are very well set up to identify and respond to disease outbreaks, the shrinking budgets at the state and local level have made that more challenging,” he said.

Stopping such outbreaks can be a logistical challenge. It requires rapid mobilization to identify the source of the disease to contain its spread. “If we find out about the first case quickly, we can often limit the amount of contact that that person may have with others while they are infectious,” said Dr. Gregory Wallace, team leader of the domestic measles, mumps, rubella and polio epidemiology team with the CDC's National Center for Immunization and Respiratory Diseases. “And if you're able to do that, the costs usually are not very high.”

Wallace, who investigates measles outbreaks for the CDC, said every case or suspected case of measles gets inspected to limit the spread of the disease. That requires checking every person who may have come in contact with an infected individual within four days after a rash appears.

All contacts are checked to make sure they have proof of immunity—either through health records that show their vaccinations are up-to-date or through a blood test result that shows they are immune or have had the disease before. The costs go up as the number of people who need to be checked increases. Once all those who were exposed have been identified, health personnel provide vaccinations or immune globulin and ensure quarantines are conducted.

“The costs really come in if the first case is not diagnosed or is diagnosed late,” Wallace said. “Then the number of contacts you have to investigate can be quite high.”

One way hospitals can speed up their response time to an outbreak and save on costs is to make sure their staffers are up-to-date on their vaccinations and their records showing their immunization information are electronically stored for immediate access. “Hospitals and their staffers are realizing that the cost associated with not being vaccinated and all of the trouble that it causes are not worth it,” Wallace said.

In 2011, the CDC's Advisory Committee on Immunization Practices published a list of recommended vaccines that all healthcare workers, including non-medical staff, should get to prevent exposure and transmission of an infectious disease. The list included vaccines for measles, pertussis and chicken pox.

Recent studies have looked at the possibility of using biosurveillance—automated monitoring systems originally designed to provide early detection of bioterror attacks—to help with early detection of natural disease outbreaks. The studies suggest that changes to the current alert systems, such as integrating primary-care physician data with data compiled from emergency rooms, could cast a broader net in identifying disease outbreaks.

In September, the U.S. Department of Homeland Security announced it planned to set up a real-time disease outbreak alert system that would search data from around the world each hour for any reports regarding cases of infectious diseases. Use of such systems might be better able to track a vaccine-preventable disease and send out early warnings to communities where immunization rates are lower and therefore are more at risk.

Immunization rates vary significantly by community, at least partly because of resistance to childhood vaccinations spurred by anti-vaccine groups that disseminate scientifically unfounded information about the risks of vaccines. Vaccination refusal is not a new phenomenon, however. Since mass immunization began in England in the early 19th century, resisters have questioned the safety and efficacy of vaccines, or have objected to their use based on the argument that requiring vaccination infringes on individual rights.

The most recent flare-up of vaccine resistance followed the 1998 publication in the Lancet of a now-discredited paper by former British surgeon Andrew Wakefield reporting evidence that the MMR vaccine (measles, mumps and rubella) was linked to an onset of autism spectrum disorders. The paper was retracted by the Lancet in 2010 because Wakefield's data were found fraudulent, and he was stripped of his medical license by the U.K.'s General Medical Council that same year.

Even though the article was discredited, since its publication the U.K. has seen a steady decline in MMR vaccinations and near-epidemic levels of measles cases. “I think people may have forgotten the original reason (for their fears), but it still casts a shadow over the vaccine,” said Stephen Morse, professor of epidemiology at Columbia University and global co-director for the U.S. Agency for International Development's Emerging Pandemic Threat Program.

Every American state requires children to get immunized by the time they are ready to begin public school. But 48 states allow exemptions based on religious beliefs, and 17 grant exemptions for philosophical beliefs. An increasing number of parents have opted to obtain an exemption for their child.

Still, vaccination coverage among children in the U.S. has remained high overall, close to the CDC's targeted rate of 95%. Vaccination rates for kindergarten-age children in 48 states and the District of Columbia during the 2012-2013 school year averaged 94.5% for MMR; 95% for diphtheria, tetanus toxoid and pertussis vaccine; and 93% for varicella (chicken pox), according to the CDC. Mississippi, which does not allow non-medical exemptions, has a rate of 99% for each of the three vaccines. Colorado, which allows exemptions, had the lowest rate, at 86%. Twenty-seven states were below the CDC target vaccination rate for at least one of the three vaccines.

Diseases such as measles with a high rate of transmission have been on the rise because of their incidence in communities where vaccination rates are low, many of them relatively affluent and well-educated. Salmon said the rise in measles and whooping cough cases has gone hand in hand with the increase in non-medical exemptions. Even though the overall rate of exemption in a state may be low, there often are communities with much higher rates.

Morse said the socioeconomic and educational status of parents seeking exemptions concerns him. “What worries me the most are the older, better educated people who for some reason think measles, mumps, rubella and other vaccines are somehow deleterious for their children,” he said.

In 2012, Washington State was hit by an epidemic of pertussis, with more than 2,500 reported cases by June of that year, the highest number in that state since 1942. Of children ages 3 months to 10 years who contracted pertussis, only about 76% had received the recommended vaccines, investigators found.

In 2010, a pertussis outbreak in California resulted in more than 9,100 reported cases and 10 deaths. A study co-authored by Salmon published in September in the journal Pediatrics found clusters of affluent, well-educated communities where the rate of non-medical exemptions was high, and that these non-medical exemptions were one of several factors behind that outbreak.

The California Department of Public Health's response to that outbreak included a public education campaign that focused on the importance of getting children and pregnant women vaccinated. Department spokesman Corey Egel said his agency worked with local health systems to better coordinate their efforts to control the outbreak, treat cases and provide post-exposure prophylaxis to those who were exposed.

“Immunization has been a victim of its own success, Morse said. “I think to some extent, people perceive the risk as being much less.”

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