So far this year, nine cases of West Nile virus have been proven. Experts in the disease say that it seems to be spreading faster than usual for this time of summer.
Up to June 25, the CDC had confirmed cases in people in at least seven states: Arkansas, Kansas, Maryland, Mississippi, Tennessee, and Northwest Arkansas. This year, the virus has been found in people, mosquitoes, birds, and other animals in at least 18 states.
Five of the cases involving humans were neuroinvasive, which means that the people got very sick, like having inflammation in the brain or the membranes that protect the brain and spinal cord. This can make you lose your balance, and your sight, go into a coma, or make you paralyzed. In the worst cases, it can even kill you.
Since there are no vaccines or treatments for West Nile, people who are very sick generally only get supportive care like fluids or painkillers.
About eight out of ten people who have the West Nile virus don’t have any signs. A smaller number of people may get a fever with headaches, body aches, joint pain, vomiting, diarrhea, or a rash. Because these signs are often mistaken for those of other viruses, most people who get West Nile are never actually identified.
The United States keeps track of between a few hundred and a few thousand cases every year. August and September are the months with the most cases.
A CDC press officer, Kate Fowlie, said in a statement, “We are seeing West Nile virus (WNV) activity a little earlier this year, so it’s really important that everyone take steps to protect themselves and their families from mosquito bites.” “WNV is hard to predict and changes from year to year, so it’s hard to say how this year will compare to others.”
Because of climate change, mosquitoes can breed faster, bite more, and stay alive for longer amounts of time. This makes people more likely to get the West Nile virus. Climate change has also made more places for mosquitoes to live.
Scott Weaver, head of the Institute for Human Infections and Immunity at the University of Texas Medical Branch, said, “There are pretty strong trends that populations are growing earlier in the year for a number of species than they would have decades ago.”
“More of them will make it through the winter if it’s warm,” he said. “Third, they will start to multiply earlier in the year if spring is warm.”
These things have also made it easier for mosquito-borne diseases like dengue fever to spread in the U.S. Late last month, the CDC warned that the country was seeing an unusually high number of cases of dengue fever: As of Tuesday, the office had seen almost 2,400 cases, down from about 3,000 cases all together last year.
Weaver said that mosquitoes that carry West Nile are most likely to be found in rural places with lots of farmland and in central states like Texas and Colorado. He also said that the Northwest and other cooler places don’t have as much West Nile activity.
Weaver said, “If it’s not warm enough, the virus moves too slowly in the mosquitoes to replicate and spread effectively.”
This year, the CDC’s number of West Nile cases is probably too low, since more human cases have been reported in several states in the last few weeks.
Since June 26, the Southern Nevada Health District has seen seven cases. On Wednesday, five of them were made public. Neuroinvasive cases made up four of the total cases. The health district said that as of June 27, more than 8,000 mosquitoes in Southern Nevada had tested positive for West Nile.
Vivek Raman, who is in charge of environmental health for the Southern Nevada Health District, said, “We had our first positive mosquitoes in May, which is pretty early because we usually see West Nile-positive mosquitoes in early July.”
Raman said that he is afraid that more West Nile will be spread during the monsoon season in the Las Vegas area, which will begin soon. Some mosquitoes do best in places that get a lot of rain or where water pools or storm drains don’t get used.
In a news release, Douglas County, Nebraska, said that the number of mosquitoes there also seems to be higher than normal for this time of year. The county said at the end of June that a blood donor had tested positive for West Nile virus.
Dr. Lindsay Huse, who is in charge of health in the county, said, “This report is worrying because it may mean that the West Nile season will start early.”
Also, the Texas Department of State Health Services reported that there was one case of West Nile virus in a person in the Houston area. Weaver told them that this summer there will be more cases in Houston.
“They’re finding a lot of virus in mosquitoes in Houston very early on,” he said. “I think that’s a bad sign of things to come.”
The woman told NBC 5 Dallas-Fort Worth that her husband died in late June from West Nile. Dranda Hopps, the woman, said that hospital workers told her that her husband had tested positive for the virus not long before he died.
The city of Springtown said on Friday that it had not yet heard from the state health department that there was a proven case. The Texas Department of State Health Services said that they may be looking into more cases that are thought to be connected.
Weaver said that West Nile surveillance is usually only done in big cities, which makes it hard to tell how common the virus is across the country.
“It’s really frustrating that we haven’t been able to figure out where West Nile infestations will happen faster so that we can put more resources there,” he said.
But some counties have come up with creative ways to find groups of infected mosquitoes. Clark County, Nevada, uses drones to find places where mosquitoes can breed, and the Scott County Health Department in Illinois has asked people to report seeing dead birds. Mosquitoes get the virus from feeding on sick birds, which is how birds naturally spread it. Illinois checks birds for West Nile to help figure out where and when people might be at risk.
Disease experts say that to lower your risk of getting sick, you should get rid of any pools or dirty flower pot saucers that hold water. You can also keep bugs out of your house by putting screens on your doors and windows.
When you’re outside, experts say to wear long-sleeved shirts and pants and use bug repellent. This is especially important at dawn and dusk, when mosquitoes are most active.