In the wake of last summer’s outbreak of deaths and illness from mosquito-borne Eastern equine encephalitis in Massachusetts, a new study by Boston researchers concludes that the risk for severe complications or death among infected children is greatest when symptoms come on quickly with little warning.
Eastern equine, a rare and virulent virus that has been on the increase in the Northeast, is often fatal and there are no specific treatments for the disease. Care focuses on relieving the symptoms, including including brain swelling and seizures.
Federal health records show that just 19 cases of Eastern equine in children were reported between 1970 and 2010 in Massachusetts and New Hampshire, and 15 of them were treated at Boston Children’s Hospital.
Dr. Asim Ahmed, an infectious disease specialist at Children’s who cared for six of the children, led a team of researchers that analyzed medical records for all 15 and found that youngsters who fared the best were those whose initial, nonspecific symptoms of illness appeared about five days before their first major neurologic problems, such as a headache or seizure.
When that time period was just two days or shorter, the outcome was much worse; all four of the deaths and those with the most severe, lingering disability occurred in this group, according to the study appearing Wednesday in Emerging Infectious Diseases, a monthly journal published by the US Centers for Disease Control and Prevention.
Ahmed said researchers hope their findings will help physicians more quickly pinpoint which patients may be more likely to suffer acute illness and death, so they can consider aggressive therapy, including surgery to relieve pressure in these patients’ swollen brains. Such pressure is common in Eastern equine infections.
He said researchers do not know why a longer time span produces more favorable outcomes, but said scientists theorize it may be related to a patient’s immune system.
“It is likely that that time represents the work of your immune system doing its thing fighting the infection,” Ahmed said. “That long phase may indicate the immune system working in a proper fashion to contain the infection.”
The length of this earliest phase of the illness appeared to be the only variable that made a difference in the children’s outcome, the researchers found. Age, symptoms, and even types of therapies used did not appear to alter the outcomes.
Ahmed noted that in 2004, he treated two children with the disease, a 13-year-old boy admitted in August of that year, and an 11 year-old girl, admitted in October. The girl, who had the longest phase of early symptoms among the 15 studied, made a full recovery. The boy, whose severe symptoms appeared to hit with no warning, died.
“The girl was as sick as the boy who died when they came in,” Ahmed said. “After waking up [from a coma] she had hemineglect, she didn’t recognize half her body. She wouldn’t know that her left hand was her, or what that even was, and who knows why.”
By the time the girl left the hospital, she had so fully recovered, you wouldn’t have been able to tell she had been sick,” Ahmed said.
“That to me,” he said “is the mystery.”
The children studied ranged in age from six months to nearly 15 years old. The findings also show that the children were as likely to die from the disease as they were to fully recover. There were four children in each category. Of the remaining seven, five were left with severe neurological deficits, often leaving them relying on wheelchairs, and two had mild to moderate problems such as learning difficulties.
Two of the children studied were from New Hampshire, which has had 11 documented Eastern equine infections since 2005, including three among children. New Hampshire public health officials said they typically send out notices in late spring to health care providers reminding them of the signs and symptoms of mosquito-borne diseases, including Eastern equine and West Nile virus, a less serious illness.
“Our infectious disease doctors will evaluate this new study and determine if we need to make any changes to our clinical messaging for 2013,” said Beth Daly, chief of infectious disease surveillance at the New Hampshire Division of Public Health.
Dr. Jose Montero, New Hampshire’s director of public health, said the study’s findings are intriguing and frustrating because some of the earliest symptoms of Eastern equine -- chills, fever, malaise -- are similar to those observed in a number of other illnesses, including stomach bugs and meningitis.Kay Lazar can be reached at email@example.com. Follow her on Twitter @GlobeKayLazar.