Los Angeles County health officials have reminded physicians to report new measles cases immediately.
In a communication distributed to medical workers at the end of last month, the county's department of public health said "a significant number" of residents had been exposed to measles when doctors delayed reporting illnesses in two county residents in January.
One man developed measles a week after returning from a trip to Asia; the second man, after exposure to a "foreign traveler."
Neither man, who have since recovered, had been vaccinated.
According to Department of Public Health Director Dr. Jonathan Fielding, 90% of people who are susceptible to measles -- a group that includes people who are not immunized -- will develop the illness after close contact with a person with the disease. Measles can be serious, causing complications such as pneumonia and even death.
"Immediate reporting is critical so we can go and prevent the spread," Fielding said Tuesday in an interview with The Times.
When the county learns of a measles case, he said, it consults with the reporting doctor, then identifies all people who have had contact with the sick person while they were contagious -- from four days before to four days after measles' telltale rash appeared.
If public health workers can intervene with contacts within three days of exposure, they can prevent disease onset; within six days, they can lessen the severity of the illness, Fielding said.
This time around, more than 40 people were exposed to the sick men, and two of them were at high risk for complications.
The disease did not spread, but the county alert to doctors noted that an infant was among the contacts and that health officials almost missed the window for administering treatment because of the reporting delay.
The U.S. Centers for Disease Control and Prevention recommends that children get their first measles-mumps-rubella vaccine when they are 12 to 15 months old, which puts infants at particular risk of infection.
By law, physicians are required to report measles cases immediately, before getting lab confirmation of measles infection. But Fielding said it wasn't surprising that doctors may not be aware of that rule, since most haven't seen measles cases in recent years.
In the last four years, he said, Los Angeles County had between three and eight cases annually. But measles cases in California are on the rise, he added, so he expects the number of local incidents to increase.
According to news reports, the Bay Area patient, a student at UC Berkeley, rode a BART train while he was sick, potentially exposing thousands of other riders to the virus.
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