A Deceptive Disease

Physicians Urged to Be Alert for Chickenpox in Vaccinated Kids

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Public Health Feature -- August 2004

By  Ken Ortolon
Senior Editor

Summer is the time for bug bites and rashes, but state public health officials warn physicians not to jump to conclusions if a child comes in with red, itchy bumps. That child just might have chickenpox, even if he or she has been vaccinated against the disease.

Officials at the Texas Department of Health (TDH) say an informal survey of school nurses, health aides, and principals shows that up to half of the state's public schools responding to the survey saw cases of "breakthrough" varicella this spring.

Breakthrough varicella is a mild case of chickenpox that occurs even if a person has been vaccinated against the disease. While it usually is less severe than chickenpox in unvaccinated people, public health officials say it is still contagious and poses a risk to unvaccinated classmates, pregnant teachers, or immunocompromised people who have never had chickenpox.

To make sure these people are not unduly exposed to varicella , pediatricians and family physicians who encounter patients with the breakthrough disease should make sure the patients stay home from school or child care centers until the lesions dry up, fade, or disappear. And, TDH officials urge physicians to be diligent about providing the varicella vaccine to all susceptible patients aged 12 months or older.

Texas officials became concerned about breakthrough varicella in May when school nurses in Denton , Arlington , and elsewhere reported that some physicians were dismissing suspected cases of chickenpox as bug bites and sending the children back to school.

"A lot of it is because the physicians see the vaccine history and, like with other diseases, once they see a history of vaccination, they automatically rule out the disease," said Rita Espinoza, MPH, an epidemiologist with the TDH Bureau of Immunization and Pharmacy Support. "It doesn't present as typical varicella so they're not recognizing it. There aren't as many lesions and they don't look like typical varicella or chickenpox lesions."

TDH officials say typical varicella consists of 250 to 500 lesions, with the rash lasting five to seven days. Breakthrough varicella has 50 or fewer lesions that last three days or less.

Monica Gamez , TDH immunization compliance coordinator, says TDH rules require any child suspected of having chickenpox to be excluded from school or day care for at least seven days.

Bug Bites or Chickenpox?

In 2000, Texas began requiring all children in public schools or child care centers to get the varicella vaccine, developed in Japan in the 1970s. However, it is not 100-percent effective.

Reported cases of chickenpox in Texas have dropped dramatically, from 20,484 in 1998 to 5,465 in 2003. Of those cases last year, 1,786 were the breakthrough variety, says TDH epidemiologist Julie Townsend , MS. The number of deaths from complications of chickenpox in Texas also has declined, dropping from 63 deaths between 1990 and 1998 to 11 from 1998 to 2003.

Breakthrough varicella has been reported also in Michigan , Oregon , New Hampshire , and Illinois . But Ms. Townsend says it is difficult to determine the number of cases nationwide because varicella is not a reportable condition in all states.

It is a reportable condition in Texas , and all suspected cases should be reported to local or regional health offices or to TDH.

"Very mild breakthrough varicella cases may not be recognized as varicella and therefore may not be reported," Ms. Townsend said. "We have a passive surveillance system, and it's likely a significant proportion of cases are never reported."

A varicella reporting form is available on the TDH Web site . The completed form can be faxed at the end of every week to TDH at (512) 458-7544.     

Dallas pediatrician Molly Ann Droge , MD, says she sees breakthrough varicella fairly frequently in her practice and admits it is sometimes hard to diagnose.

"With typical chickenpox you see a variety of different stages," she said. "You see the small red bump going to the vesicle, and then it pops open and crusts over. So everyday you get a new crop of that sequence of lesions. With the post-vaccine chickenpox disease, it's not always as clear-cut that they are different varieties of lesions. There may be only a couple of different looking kinds. The fact that they are itchy does not seem to help because bug bites can be itchy, too."

Dr. Droge says the best way to tell if it is chickenpox rather than bug bites is to look for lesions inside the mouth or ear. "There may be some misdiagnosis, but if you see lesions in the mouth or inside the ear or on the scalp under the hair, then it's much more likely to be chickenpox."

Inquiring about possible recent exposure to chickenpox may also tip a physician to a potential case of breakthrough varicella .

Researchers at Yale University School of Medicine have been conducting a case-control study of breakthrough varicella since 1997. In an article published in the Feb. 18 issue of the Journal of the American Medical Association , they concluded that it's virtually impossible to distinguish clinically between breakthrough varicella and other types of bumps or rashes.

The Yale group concluded that persons who suspect that they or their children have chickenpox should seek medical attention or stay home until the rash disappears.

Ken Ortolon can be reached by telephone at (800) 880-1300, ext. 1392, or (512) 370-1392; by fax at (512) 370-1629; or by email at Ken Ortolon.

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