JMM Profile: West Nile virus.

This research article is about the West Nile virus (WNV), an RNA virus that typically spreads between mosquito vectors and bird hosts, but can also infect mammals including humans and horses. The article describes the disease symptoms which can range from mild fever to severe encephalitis, and mentions that there are currently no licensed vaccines for human protection.

West Nile Virus and Its Cycle

• West Nile Virus (WNV) is a type of RNA virus that falls under the Flaviviridae family.
• The virus is maintained primarily in a cycle between avian hosts and mosquito vectors. This cycle involves the virus being transmitted from infected birds to mosquitos who then go on to infect other birds, continuing the cycle.
• Mammals including humans and horses can also be infected by the virus, however they are referred to as “dead-end hosts”.
• This is because these mammals, after getting infected, do not produce enough of the virus in their blood to contribute to the transmission cycle, making them a kind of biological “dead end” for the virus.

Clinical Signs and Symptoms

• The symptoms of West Nile Virus in humans and horses can vary greatly in severity.
• It can cause mild fever in some cases, but in severe cases it could lead to encephalitis, a type of brain inflammation that can increase morbidity rates.
• Morbidity refers to the number of people who have a disease compared to the total number of people in a population. In this context, it means that encephalitis can increase the number of people who are ill in a population.

Availability of Vaccines

• Currently, there are no vaccines available that are licensed for protection against the West Nile Virus in humans.
• However, in certain regions such as parts of Europe, North America, Africa, and Australia, vaccines are commercially available for horses.