Florida fears massive outbreak of West Nile virus

2019-03-06 11:06:22

By Catherine Zandonella The discovery of West Nile virus disease in a Florida man has public health officials wondering if the state – which is heavily populated with mosquitoes and elderly people – could be the scene for a massive outbreak of the disease. A study of the 1999 outbreak in New York published in the Lancet on Friday shows that up to 13,000 people were infected. A similar infection rate in Florida’s elderly population could have severe consequences since the elderly are much more susceptible to the disease caused by the virus. Mosquitoes transmit the virus. Steven Wiersma, the state epidemiologist for Florida, says his staff is very concerned about the risk for the elderly. “We are definitely telling people over 50 years old to protect themselves from mosquitoes.” West Nile virus is entering its third year in North America after arriving in New York, presumably on an intercontinental flight or ship. The virus is especially lethal in crows and horses, but can also infect cats, reptiles and humans. The analysis of the 1999 outbreak found that between 3500 people and 13,000 people, or an average of 2.6 per cent of the population in the area, were infected. The majority never experienced symptoms, but approximately 20 per cent reported a flu-like fever and one per cent succumbed to a deadly brain-swelling disease called meningoencephalitis. Elderly and immuno-compromised people are most at risk of encephalitis, for which there is no cure or vaccine. Florida’s humid summers and mild winters make it attractive to retirees and mosquitoes alike, a potentially deadly combination. “The age distribution of the population definitely affects the likelihood of a patient progressing to encephalitis,” said Farzad Mostashari, the lead author of the New York study and an epidemiologist with the New York City Department of Health. Since the virus entered the continent, nine people have died from the disease, seven in 1999 and two last year. This year’s only case to date, 73-year old Seymore Caruthers of Madison County, Florida, remains in hospital in critical condition. The demographics of the 1999 outbreak are similar to previous outbreaks in Israel, the Czech Republic and other countries, says Mostashari. Scientists at the Centres for Disease Control and Prevention (CDC) are monitoring the virus for mutations that might indicate the virus is becoming more virulent, says Stephen Ostroff, a medical epidemiologist at the CDC headquarters in Atlanta, Georgia. So far detection of the virus in Florida has been confined to a rural area, but Thursday’s discovery of an infected bird in the county adjacent to the City of Orlando might indicate it is spreading to more populated areas. What might save Florida is the state’s active disease surveillance system, which includes sentinel chickens that periodically have blood drawn to check for virus. Already one chicken has tested positive. Across the US, states have set up monitoring programs, and several states are spraying for mosquitoes and advising individuals to report any dead birds they find. When asked if he thought the virus would spread to every state, Ostroff replied, “There is no reason that it can’t.” Journal reference: The Lancet (vol 358,