ویسٹ نائل اینکیفلائٹس کی وجہ ویسٹ نائل وائرس نامی جرثومہ ہے جو کے ڈینگی وائرس کے گروپ سے تعلق رکھتا ہے۔ یہ وائرس ابتدائی طور پر پرندوں میں پائے جاتے ہیں اور ان پرندوں کو کاٹنے والے مچھر اس وائرس کے انسانوں میں پھیلائو کا باعث بنتے ہیں۔ اس وائرس سے متاثرہ ستر سے اسی فیصد افراد میں کئی علامات ظاہر نہیں ہوتی جب کہ بیس سے پچیس فیصد لوگوں میں بخار کی شکایات سامنت آتی ہیں۔ صرف ایک فیصد لوگ ایسے ہیں جن میں یہ وائرس اعصابی بیماری ویسٹ نائل اینکیفلائٹس کا باعث بنتا ہے۔
The West Nile Virus causes the West Nile Encephalitis. The family that this virus belongs to also consists of viruses that cause other illnesses like Japanese encephalitis and the dengue fever. These viruses are known to be present primarily in birds; seventeen species of birds carry this virus. The Culex, Aedes, and Anopheles mosquitoes basically bite on and suck this infected blood from the birds and transmit the virus when they then bite a human being.
Mosquitoes are responsible for transmitting this virus from birds to mammals. However, mammals do not make ideal hosts. The disease, because of this, seldom transmits from one human being to the other. Around 70-80 % of those who have this virus display no symptoms at all and about 20-25 % show symptoms of a fever. However, around 1 % of people with the West Nile Virus end up developing a neurological disease, or WNE.
It is possible that WNE patients display several symptoms of varying levels of severity. They might exhibit characteristics of encephalitis and/or aseptic meningitis (meningoencephalitis). These symptoms will be most evident in either very young or very old people. The way the symptoms are expressed, and what symptoms are expressed, reflect the severity of the invasion of the virus in the CNS.
The symptoms observed are:
The main reasons for the transmission of West Nile Encephalitis are mosquito bites. Several patients are not aware, or are not able to provide a history of the mosquito bites that they have had, even though the period of incubation in 1-6 days for WNE. An important risk factor is the time of the year; WNE typically spreads in the season summer. This is because of the high influx of mosquito population and the presence of birds of migration. Humans staying outdoors also puts them in a closer proximity with the mosquitoes. More exposure to mosquito bites that occur especially frequently in the times of dusk and dawn can increase the risk for the transmission of WNE.
It is also possible that breast-feeding and organ transplant can spread WNE from one to another as well.
The most easy and simple way to prevent WME is to prevent the mosquito bites from occurring in the first place. This can be possible through a variety of ways, including measures such as covering oneself up properly, particularly in the times when mosquito bites are most likely to happen: evenings. Wearing of mosquito repellant and avoiding usage of perfumed products during the evening which can attract mosquitos can also help. Another important measure can be to not let water stagnate anywhere as mosquitos tend to lay their eggs there.
At the present moment, there are no vaccines which could stave off the West Nile virus, so it is important that the above mentioned measures be properly observed.