Since arriving in North America in 1999, West Nile virus (WNV) has infected tens of thousands of people, with the majority of cases taking place in August and September. The reason WNV appears more during the ‘Dog Days’ of summer is because those are the peak times for the infected mosquitoes who transport the virus.
However, while a simple mosquito bite may not seem like a big deal to many, around 15 percent of people infected will experience unpleasant symptoms, similar to a fever, but there are also some short and long-term effects which can be even more dangerous…
A viral infection is an infection caused by the presence of a virus in the body. The problem with viral infections is that they can infect almost any type of body tissue. That includes organs like the brain. West Nile fever is caused by such a viral infection, typically if not always transported by infected mosquitoes.
Signs of Infection
Only 15 to 20 percent of people affected will show symptoms, while the others wouldn’t notice anything out of the ordinary; other than an annoyingly itchy bite on the skin.
While roughly 75 percent of people infected will feel nothing and not even know they have WNV, the 15 to 20 percent of people that do develop symptoms may develop a bad headache, begin to vomit and in some cases, see a spreading rash on the skin.
The One Percent
Then there’s the rare one percent of people who can suffer from serious conditions as a result of being bitten, such as encephalitis or meningitis. Recovery from such conditions can take weeks or even months, but there’s also a risk of the virus affecting the nervous system long-term.
While mosquitoes are the culprits who carry the virus, it doesn’t originate from them. The mosquitoes become infected after they feed on infected birds (usually dead ones). However, if someone does display the more worrying symptoms of the virus, blood tests will be carried out to ascertain if it’s WNV or something else.
West Nile Virus has been found in more than 250 species of dead or dying birds. However, scientists have discovered that birds in the crow family are particularly susceptible to the virus.
Like humans, horses can become infected with the virus, however, they also do not typically spread the infection.
Other Forms of Transmission
While most cases are the result of a mosquito bite, the virus can also be transmitted through contact with other infected animals, their blood, or other tissue. Infections have also occurred through organ donation, blood transfusions, and breast milk.
While the whole subject of vaccines and immunizations is a controversial one in itself, there currently exists no vaccine to counteract the West Nile Virus. As such, the only way to ensure one doesn’t get infected is not to get bitten by a WNV carrying insect, which is difficult to control. For the time being, the only thing to do if you are bitten and affected badly is to take some anti-histamine and possibly some pain medication.
For patients who are hospitalized with neuroinvasive West Nile virus, doctors can only offer supportive treatments like intravenous fluids, respiratory support, and prevention of other infections.
Mosquitos are particularly attracted to people wearing dark clothes. The flying pests are also attracted to heat, lactic acid, and carbon dioxide, which is why people working out get bitten more.
How to Prevent a Bite
The World Health Organization recommends everyone protect themselves against mosquito bites by using mosquito nets, personal insect repellent, wearing light colored clothes, wearing long sleeves and pants, and to avoid outdoor activities around peak biting times.
Not Just Stateside
The West Nile Virus hasn’t just reached the shores of the United States. Europe, Africa, Asia, and Australia have also had their fair share of the virus, although due to population numbers, the U.S often leads the pack in terms of annual numbers. Having first been discovered in Uganda back in 1937, it took many years for the virus to make its way west, even if that eventuality was anticipated.
To get technical for just a moment, even patients with apparently mild cases of the virus can often suffer from subjective, somatic complaints. These complaints include but are not limited to limb weakness and neurological disorders which can in some cases be life-threatening. The emergence of the WNV epidemic in America is a reminder for science as to the ability of new viruses to emerge unexpectedly and even thrive in the most unlikely of settings.
At Risk Populations
Anyone exposed to the virus are at risk of serious illness, however, people over the age of 50 and people with compromised immune systems have a higher risk of getting severely ill from West Nile virus.
Back in 2006, when the virus was at a peak in the U.S., more than 23,500 cases of West Nile Virus were reported, including 904 cases which resulted in death, according to the Center for Disease Control and Prevention. But the issue is long-term effects of the virus on people who didn’t even know they were infected in the first place. While the long-term effects are more difficult to assess than the short-term effects, they represent a source of ongoing morbidity.
Outcomes of WNV
Interestingly, outcomes of human WNV infection in Africa and many parts of the Middle East have historically only resulted in mild symptoms, with only a small percentage (mainly children) noticing any more serious or long-term effects. While some outbreaks in Israel and some parts of Europe followed the U.S. model more closely, they have seen a more frequent development of neurological illness in those countries.
More Significant Problems
During the early years of the WNV outbreak in the U.S., no one was overly worried about the long-term effects of a virus which appeared not to be affecting that many people that badly. However, more recent data suggests that the virus may be associated with more-significant ongoing problems than were initially found. While age is definitely a factor, many people may have no idea that they are suffering acute symptoms due to having been bitten by a WNV mosquito.
North Dakota Study
A study carried out on 49 North Dakotans who had suffered from at least one symptom after a West Nile viral infection revealed some interesting but worrying results. As already mentioned, only one in five people infected with the virus will notice it, enduring a flu-like illness known as West Nile fever. Doctors call the symptoms, a “benign, self-limited illness,” but this study showed that results could be a lot more negative.
One Year Later
Researcher Paul J. Carson, M.D., from the University of North Dakota, spoke to reporters about the worrying findings from the study. Carson noted, “Our patients continued to show clinical abnormalities one year after illness … Patients with ‘milder’ illness – that is, non-hospitalized patients with West Nile fever – demonstrated equivalent rates of these abnormalities.”
The year 2003 was a big one for the West Nile virus in the US. During that year, almost 10,000 new cases of the virus were reported, with 617 of them hailing from North Dakota. Carlson and his team attempted to track down the 122 infected North Dakotans known to the state. Carlson then persuaded 49 of those people to submit a number of tests, which included measuring psychological and neurological function.
While 80 percent of those patients had contracted West Nile fever at the time, the other 20 percent had suffered from a confirmed West Nile infection with symptoms. The scary part is that those people were all diagnosed with an infection of the brain or the lining of the brain and spinal cord. Fortunately, only one patient from the 49 had the most severe form of the virus, which caused a polio-like paralysis.
The issue here and the thing that Carlson was trying to figure out was why a year after being infected, around half of the patients reported poor physical health. Symptoms like fatigue, memory problems, weakness, headache, joint pain, and balance problems were among the bunch, while a third of those patients had been hospitalized. Interestingly, one in four of the respondents reported suffering from depression, which they believe was connected to WNV.
Possibly the most chilling and worrying results found by Carlson and his team were from the numerous psychological and neurological tests which were carried out. Of the patients tested who hadn’t even been admitted to a hospital after they were infected, at least 15 percent said they had, “moderate-to-severe impairment of executive function.” But the finger tapping test revealed even stranger results.
The subjects undertook a finger-tapping test along with the other tests to ascertain their motor speed. Worryingly, a massive 70 percent of the patients showed some form of abnormal results during the test, while in 43 percent, motor skills impairment was classed as “severe.” The researchers concluded that the people in the 43 percent were the most likely to suffer from depression.
Some Good News
Despite the issues with motor skills and depression, most of the patients tested were able to return to a “reasonable level of daily function.” And that explains why previous studies found better long-term results for WNV as they only looked at disabilities and not things like motor skills and mental impairment. As such, Carlson believes the WNV is a brain infection which leaves long-lasting damage in its wake.
Back to the present day and a recent report out of North Dakota, which notes that the head of the mosquito control program of the Grand Forks Public Health Department, Todd Hanson, said his department will be taking “aggressive action” this year when it comes to countering what they consider to be an “elevated threat of West Nile virus … We are finding mosquitoes and birds that are positive for West Nile virus on a weekly basis.”
Don’t be Fooled
Hanson warned residents not to be fooled by the lack of mosquitoes this year, as the ones which are around may well be carrying the virus, “We don’t have a lot of nuisance mosquitoes right now, so people tend to think that mosquitoes are not that bad,” he said. “But we are reaching peak season for West Nile virus, which is pretty much all of August. That’s generally when the highest number of human cases is reported.”
Hanson urged residents to take full precautions where possible, and not to assume that mosquitoes are only a threat at night. Hanson said that while residents “think they don’t have to take precautions, now is the time they need to be vigilant about this,” adding, “Personal responsibility is the most important part. Apply mosquito repellent and wear protective clothing.” Hanson concluded that “all it takes is one mosquito to bite you and transmit that virus to you.”
Mosquitos breed in standing water, so people should empty water from things like flower pots, buckets, and kiddie pools. People should also change the water in pet dishes and birdbaths regularly.