Calming West Nile fears

Although children appear to be at low risk for the virus, pediatricians should be on lookout for the mosquito-borne disease

Kristy Kennedy
Correspondent
AAP News - September, 2002

When West Nile virus broke out in New York City, callers flooded public health phone lines asking questions such as whether children should play outdoor soccer. Those bitten by mosquitoes rushed to emergency departments. Schools canceled outdoor field trips.

Anxiety was high in 1999, when the disease made its first appearance in the Western Hemisphere, said Kristine Smith, who fielded many of the calls as associate director of public affairs for the New York State Department of Health.

“Wherever you see an outbreak, you will see a great deal of public concern, especially among parents. Because doctors are the most trusted communicators with their patients, they need to be prepared to answer questions,” said Smith, who chaired a statewide West Nile virus risk communications workgroup.

Pediatricians, however, need not scare parents about mosquitoes, added Larry K. Pickering, MD, FAAP, editor of the 2000 and 2003 AAP Red Book: Report of the Committee on Infectious Diseases. But parents of children with numerous mosquito bites should be reminded to rid their yards of standing water, dress their children in long sleeves and pants when outside at dawn or dusk, and to use bug spray appropriately.

For the few minutes pediatricians have with patients and parents, Dr. Pickering prefers they talk about seat belts. After all, children probably are at greater risk during the car ride to the soccer game than from contracting West Nile virus while playing soccer. But just as most parents buckle up their children to keep them safe, they also should take precautions against mosquitoes in infected areas, he said.

Virus spreading rapidly

West Nile virus, which causes encephalitis and meningitis in serious cases, likely will be found across North America at some point. A NASA-funded study is using satellite maps of bird migration, weather patterns and vegetation growth to track and help predict where outbreaks may occur.

Since the New York outbreak in 1999, the virus has been detected in 37 states as far west as Texas and in Canada.

“It has been relatively rapid as these things go,” said Stanford T. Shulman, M.D., FAAP, division head of infectious disease at Children’s Memorial Hospital in Chicago and professor of pediatrics at Northwestern University’s Feinberg School of Medicine.

Most cases are mild, with people showing no symptoms or having a fever, headache and body aches. Other symptoms include a mild rash, swollen lymph glands, severe headache, high fever, stiff neck, confusion, seizures, aversion to light, muscle weakness and loss of consciousness. It is thought that infected people develop a lifelong immunity to the disease.

In the New York outbreak, 67 people became ill. Symptoms of West Nile virus encephalitis seemed to include more muscle weakness than in other forms of encephalitis, said Dale Morse, MS, MD, director of the office of science and public health at the New York State Department of Health. In serious cases, patients had to be hospitalized about four days after the onset of symptoms.

Because most victims suffer symptoms that are common to other viruses, the disease is underreported, Dr. Pickering says. As of August 14, 156 human cases of West Nile virus encephalitis or meningitis had been reported and 9 people had died, according to the US Centers for Disease Control and Prevention (CDC). More cases were expected as the season progressed. Last year, 66 cases were reported in the United States.

West Nile virus was discovered in the West Nile District of Uganda in 1937 and has been detected in Africa, Europe, the Middle East and west and central Asia.

Most of the serious US cases to date have involved the elderly, according to the CDC. Only 1% of people bitten by infected mosquitoes become seriously ill and of that group, 3% to 15% of cases are fatal.

Put risk in perspective

So far, children appear to be at low risk for the disease, although the youngest person in New York to become seriously ill was 5 years old, Smith said.

Despite the low risk, pediatricians need to be on alert for the disease. One reason is it is too early to tell how the disease will behave as it spreads, said Dr. Morse, who oversaw the lab that first recognized the West Nile outbreak in New York. “It likely will be different in different parts of the country,” he said.

For example, mosquitoes most likely to carry the disease bite primarily at dawn and dusk. But if the disease were to spread to mosquitoes that bite all day long, more people, including children, could become infected, Dr. Morse said.

Pediatricians should put that risk in perspective, experts caution. The hype over West Nile virus has been “somewhat out of proportion,” Dr. Pickering said, noting other arboviruses that cause encephalitis and meningitis are more serious.

West Nile virus is in the family of arboviruses affecting the central nervous system. Others include California encephalitis (primarily La Crosse virus), Eastern equine, Powassan, St. Louis, Venezuelan equine and Western equine. All are spread by mosquitoes except Powassan encephalitis virus, which is tick-borne. After biting an infected bird, a mosquito transmits the virus to humans or domestic animals. People and animals can’t spread the disease to each other (2000 AAP Red Book, pp. 170-175).

“It is not surprising that there is a lot of attention focused on (West Nile virus),” said Dr. Shulman, chair of the AAP Section on Infectious Diseases. “But to keep it in perspective, this is one of many causes of encephalitis that we encounter particularly in the warmer months of the year. Physicians need to have a great deal of respect for the potential seriousness of the arboviral infection. Within that group, there are several that are quite serious, and some are more common in children than adults.”

Eastern equine is the most deadly of this group of arboviruses, and La Crosse is the most common in children.

Importance of surveillance

Because there is no cure for encephalitis, it does no good to determine the exact cause of the illness in an individual patient. But Drs. Pickering and Shulman encourage doctors to pinpoint the cause of arboviral encephalitis to help public health officials track and control outbreaks.

“Reliable reporting is the cornerstone of any epidemiological investigation,” said Shaffiq Essajee, MD, assistant professor of pediatrics at New York University.

States where the virus has been found are counting birds, most commonly crows, that have died from the disease. However, reports of dead birds in New York are down, said Smith. “Now we have to be concerned about public complacency,” she said.

Still, cases of the disease have plummeted in New York over the last two years. Only 14 cases were reported in each of 2000 and 2001.

“This is a testament to the success of the city’s mosquito control program,” Dr. Essajee said. “Although we need to be vigilant and certainly we should be concerned about the rapid spread of West Nile virus, this does not necessarily imply an inevitable plague of human West Nile virus disease.”

Updated information is available at www.cdc.gov/ncidod/dvbid/westnile/index.htm