The Centers for Disease Control and Prevention held its second media briefing in as many weeks to provide an update on this year’s surge in West Nile virus cases.
As of Aug. 28, the CDC had received reports of 1,590 cases of West Nile virus disease in people, including 66 deaths. The number of reported cases is the highest through the last week in August since the virus first was detected in the United States in 1999. More than 70% of reported cases have been in Texas, South Dakota, Mississippi, Oklahoma, Louisiana and Michigan, with nearly half in Texas.
Of the reported cases, 889 (56%) were classified as neuroinvasive disease, such as meningitis, encephalitis or acute paralysis. The numbers represent about a 40% increase over last week’s report of 1,118 total cases, 629 neuroinvasive disease cases and 41 deaths.
Only about 2% to 3% of people with non-neuroinvasive West Nile virus illness are diagnosed and reported to national surveillance, said Lyle Peterson, MD, MPH, director of the CDC’s Division of Vector-Borne Illnesses. The CDC does not recommend routine testing for non-neuroinvasive disease because there is no specific treatment. "There are a number of logistical problems that have made clinical trials for treatment very, very difficult in practice," Peterson said.
Peterson said that because cases of non-neuroinvasive disease — West Nile fever — are substantially underreported, cases of neuroinvasive disease are the best measure of the severity of the epidemic.
"Based on current reports, we think the numbers may come close to or even exceed the total number reported in the epidemic years of 2002 and 2003, when about 3,000 cases of neuroinvasive disease and more than 260 deaths were reported each year," he said.
Peterson said Hurricane Isaac, which hit the Gulf Coast on Tuesday and Wednesday, likely will have no noticeable effect on the current West Nile epidemic. He did say small increases in the number of cases were noted in some areas of Louisiana after Hurricane Katrina in 2005. "These were thought to be due to increased outdoor exposure that occurred when houses were severely damaged and during recovery efforts," Peterson said.
The CDC has no evidence to suggest this year’s outbreak was caused by a genomic change in the virus. However, it continues to investigate that possibility, Peterson said.
"We encourage everyone to use insect repellent when you go outdoors, wear long sleeves and pants," Peterson said. "Use air conditioning if possible. Empty standing water from items outside your home, such as gutters, kiddie pools and birdbaths."
People with kidney disease, cancer or other immune-compromising conditions face a higher risk of contracting West Nile virus disease, as do people who take immunosuppressants after an organ transplant or because of rheumatoid arthritis or other conditions.
More information about West Nile virus from the CDC is available at www.cdc.gov/ncidod/dvbid/westnile/index.htm.
As of Aug. 28, the CDC had received reports of 1,590 cases of West Nile virus disease in people, including 66 deaths. The number of reported cases is the highest through the last week in August since the virus first was detected in the United States in 1999. More than 70% of reported cases have been in Texas, South Dakota, Mississippi, Oklahoma, Louisiana and Michigan, with nearly half in Texas.
Of the reported cases, 889 (56%) were classified as neuroinvasive disease, such as meningitis, encephalitis or acute paralysis. The numbers represent about a 40% increase over last week’s report of 1,118 total cases, 629 neuroinvasive disease cases and 41 deaths.
Only about 2% to 3% of people with non-neuroinvasive West Nile virus illness are diagnosed and reported to national surveillance, said Lyle Peterson, MD, MPH, director of the CDC’s Division of Vector-Borne Illnesses. The CDC does not recommend routine testing for non-neuroinvasive disease because there is no specific treatment. "There are a number of logistical problems that have made clinical trials for treatment very, very difficult in practice," Peterson said.
Peterson said that because cases of non-neuroinvasive disease — West Nile fever — are substantially underreported, cases of neuroinvasive disease are the best measure of the severity of the epidemic.
"Based on current reports, we think the numbers may come close to or even exceed the total number reported in the epidemic years of 2002 and 2003, when about 3,000 cases of neuroinvasive disease and more than 260 deaths were reported each year," he said.
Peterson said Hurricane Isaac, which hit the Gulf Coast on Tuesday and Wednesday, likely will have no noticeable effect on the current West Nile epidemic. He did say small increases in the number of cases were noted in some areas of Louisiana after Hurricane Katrina in 2005. "These were thought to be due to increased outdoor exposure that occurred when houses were severely damaged and during recovery efforts," Peterson said.
The CDC has no evidence to suggest this year’s outbreak was caused by a genomic change in the virus. However, it continues to investigate that possibility, Peterson said.
"We encourage everyone to use insect repellent when you go outdoors, wear long sleeves and pants," Peterson said. "Use air conditioning if possible. Empty standing water from items outside your home, such as gutters, kiddie pools and birdbaths."
People with kidney disease, cancer or other immune-compromising conditions face a higher risk of contracting West Nile virus disease, as do people who take immunosuppressants after an organ transplant or because of rheumatoid arthritis or other conditions.
More information about West Nile virus from the CDC is available at www.cdc.gov/ncidod/dvbid/westnile/index.htm.
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