Public health officials on Thursday warned of a sharp increase in viral meningitis this summer, mostly afflicting children, in three of Southern California's inland counties.
More than 400 cases have been reported in San Bernardino, Riverside and Imperial counties so far this year, compared with 114 over the same period last year.
Health experts so far have not pinpointed a cause of the outbreak. Meningitis most often causes headaches, fevers and stiff necks and rarely causes serious or permanent health complications or death.
Some experts speculated that greater awareness of the West Nile virus, which can cause viral meningitis, has made some health care providers more cognizant of the illness and thus there has been increased reporting. However, a San Bernardino County health officer said the reason may be linked to the virus itself.
"I really think, more than likely, it may be caused by a virus circulating that has not been common in the area before," said Dr. Tom Prendergast. "People therefore haven't had a chance to build an immunity to it."
Whatever the reason, the increase has astonished some health officials.
"Every summer there's an increase, but this dramatic a jump is unexpected," said Dr. Eric Frykman, chief of San Bernardino County's disease control and prevention division. The San Bernardino County Department of Public Health has recorded 176 cases of the disease through Tuesday, compared with 68 cases last year during the same time period.
Riverside County has had 91 cases of viral meningitis through July of this year, compared with 27 last year.
In Imperial County, with a sparse population of about 150,000, 140 cases have been reported so far this year, a massive jump from only 19 last year, and only a dozen the year before.
Although officials said there has been an increase in hospitalizations because of the illness, no deaths or serious health complications have been reported.
Until June, monthly reports of viral meningitis in San Bernardino County were about the same as they had been for the past two years. But those numbers doubled this June. In July, the difference was much greater: 97 cases were reported, compared with 14 cases last July. During the first five days of August, 19 cases were reported in the county. Only five cases were reported during all of August last year.
Viral meningitis is rarely fatal. The illness causes an inflammation of the tissues surrounding the brain and spinal cord. Common symptoms are fever, severe headache, sensitivity to light, drowsiness, nausea and a stiff neck. Unlike bacterial meningitis, it's almost unheard of for viral meningitis to cause severe brain damage or death, Prendergast said.
The symptoms are similar to those of the West Nile virus, caused by infected mosquito bites. But no West Nile virus cases have been detected in California this year, officials said.
But because viral meningitis can be a sign of West Nile virus, some health officials fear that the outbreak is an indication that West Nile has arrived.
"The real concern is because there have been projections that West Nile will hit Southern California sometime this year," said Barbara Cole, director for disease control for the Riverside County Department of Public Health. "West Nile can cause viral meningitis."
Most people with viral meningitis completely recover in seven to 10 days, authorities said.
Viral meningitis is most often spread through unsanitary conditions, such as failure to wash hands. Children sharing drinking containers and using non-chlorinated wading pools are also at risk. Babies with the virus are difficult to wake up and suffer a loss of appetite.
"Hand-washing, hand-washing, hand-washing: that's what we're trying to reinforce to the community," said Paula Kriner, an epidemiologist for the Imperial County Public Health Department.
Although some of the cases have been linked to a patient's family members, the outbreak in Imperial County has mostly been scattered, she said.
The National Center for Infectious Diseases also recommends thorough hand-washing to help prevent the spread. Child care centers and other institutions where children share confined spaces can wash objects and surfaces with a diluted bleach solution.
The affected counties are working to get the word out about the rise in viral meningitis cases to health providers, the public and other institutions.
Christine McGrew, spokeswoman for San Bernardino County superintendent of schools, said, "We'll be working with the health department to issue information to districts, school administrators and school nurses to alert them to the heightened number of cases so they can be watchful of students who exhibit symptoms."