Young child diagnosed with measles in northern Virginia

Liz Szabo | USA TODAY

Doctors are investigating whether a small child hospitalized for measles in northern Virginia early this month infected others, local health officials said.

Health department staff want to know how the child contracted the disease, said John Silcox, a spokesman for the Fairfax County Health Department in the suburbs of Washington, D.C. Measles is one of the most contagious of all viruses and spreads easily through the air when people cough or sneeze.

"There's never just one measles case," said William Schaffner, a professor and infectious disease specialist at the Vanderbilt School of Medicine in Nashville, who is not involved with the investigation.

As of Sept. 18, there have been 189 measles cases in the USA, according to the CDC, with 117 of them related to a nationwide outbreak that originated at Disneyland in late 2014. A woman in Washington state died of measles in July, the first measles death in the United States in 12 years. There were 667 measles cases in the USA in 2014, mostly due a large outbreak among the Amish in Ohio. Many of the measles cases last year were linked to the Philippines, which had a massive outbreak.

In many cases, Americans are exposed to measles when they travel overseas or have contact with an unvaccinated person who returns from overseas, said Paul Offit, chief of the division of infectious diseases at Children's Hospital of Philadelphia.

The child had not traveled overseas, Silcox said, suggesting that the youngster was exposed to measles in the United States.

Virginia health officials did not reveal the age of the child, but said the youngster may have exposed others at a local daycare center Sept. 30 or a Costco Wholesale Club and pediatrician's office the next day. The child also may have exposed people at Inova Fairfax Medical Campus in Falls Church, Va., when the child went to the emergency room. The child was later admitted to the hospital.

The child had received one measles vaccine, which is recommended at ages 12 to 15 months. The child is apparently too young to have received the second recommended dose, typically give at ages 4 to 6 years.

While it's relatively unusual to see measles in a vaccinated child, Schaffner noted that "no vaccine is 100% effective." The vast majority of measles occurs in people who haven't had any vaccine.

One dose of measles vaccine is about 92% effective, Schaffner said. About 91% of Virginia children ages 19 to 35 months received a first dose of the combined measles-mumps-rubella vaccine in 2014, according to the Centers for Disease Control and Prevention.

Public health officials are increasingly concerned about the rise in measles cases, which have grown as more parents choose not to vaccinate their children because of a mistaken belief that vaccines cause autism. Multiple studies have found no link between autism and any vaccine.

Schaffner said the Virginia child's case is typical, in that people with measles often expose many others when they go to a doctor's office. Few parents today are familiar with measles, whose early symptoms include fever, runny nose, cough and red, watery eyes. A red rash breaks out three to five days after symptoms begin, according to the CDC. Schaffner notes that even many doctors and nurses may not recognize measles.

The virus can be serious, killing one to two out of every 1,000 children infected, according to the World Health Organization. One in 20 children who contract measles also get pneumonia. Those most at risk from measles are people with weakened immune systems, such as those undergoing cancer treatment, as well as babies too young to have received their first measles vaccine, Offit said.