Arbovirosis

Viruses and mosquitoes: origin and differences of Dengue, Chikungunya and West Nile

In the past, these infections were referred to as 'exotic' or 'rare': there are no specific therapies, prevention remains the best weapon against infection

by Ernesto Diffidenti

31 July 2025

Disinfestazione in alcune aree di Panama City, Panama, nell’ambito di una "mega operazione interistituzionale contro la dengue". EPA/Carlos Lemos

4' min read

Key points

The different origins of viruses and names
Chikungunya in Italy since 2007
Symptoms triggered by Dengue
West Nile: Birds are the reservoirs of the virus
For all viruses, the main rule is to prevent infection.

4' min read

When in Rome, do as the mosquitoes do. But as a result of globalisation, i.e. the long and frequent journeys of people and goods to different continents, it also happens that you find them all in the same country. This is happening to Italy, which is hosting colonies of mosquitoes that transmit the dreaded Dengue, Chikungunya and West Nile viruses.

Once, not so long ago, these infections were referred to as 'exotic' or 'rare'. But today, with the complicity of climate change and the migratory movements of birds and insects, they occupy the front pages of newspapers and have entered by right among the concerns of citizens who have begun to learn about arboviruses.

But what are they? They are infectious diseases caused by viruses that are transmitted to humans and other animals through arthropod vectors such as mosquitoes, ticks, through the bite or sting. The virus is not transmitted from human to human.

The different origins of viruses and names

The names of the infections, Dengue, Chikungunya, West Nile, hark back to distant worlds and languages. Dengue is also known as 'bone-crushing fever' for the pains it causes precisely at skeletal level, while the term Chikungunya, of African origin, means 'that which bends or twists' for the particular joint pains that force one into a defensive and immobile position. The mosquito of the genus Aedes, the so-called 'tiger mosquito', is responsible for these two infections. It spread to Italy in the early 1990s, when it first landed in Genoa together with a load of tyres from the USA. The name 'West Nile', on the other hand, derives from the district in Uganda where the virus was first isolated in 1937, based on the whereabouts of a woman who presented with febrile symptoms. The virus, therefore, takes its name from the region where it was discovered, which is why in Italy it is also known as 'Nile fever'.

Chikungunya in Italy since 2007

With regard to Chikungunya, the first cases with local transmission in Italy date back to 2007. After being bitten by a mosquito carrying the virus - as reported on the Epicentre website of the Istituto Superiore di Sanità - the incubation period ranges from 3 to a maximum of 12 days. This is followed by sudden onset of fever and pain in the joints, such as to limit the movement of patients, who tend to remain absolutely motionless and in crouched positions. Symptoms also include muscle pain, headaches, fatigue and skin rash. In most cases, patients recover completely, but joint pain may persist for months and even years. Serious complications rarely occur, but in the elderly the disease can be a contributory cause of death.

To date, there is no cure and treatments are symptomatic, although a vaccine has recently been approved in the USA, which is not available in Europe.

Symptoms triggered by Dengue

The Dengue virus has humans as its main host, but there is no direct contagion between humans: it circulates in the blood of the infected person for 2 to 7 days, and if a mosquito bite occurs during this period, the mosquito can transmit it to others. 5 or 6 days after the bite, if the disease develops, one may experience a very high fever, acute headaches, pain around and behind the eyes, severe muscle and joint pain, nausea and vomiting, and skin irritations that may appear on most of the body 3-4 days after the onset of the fever. It usually heals completely within 2 weeks. Rarely, the infection can evolve into haemorrhagic fever - which occurs mainly in a second episode of infection - with severe haemorrhages that can cause actual collapse and, although in rare cases, prove fatal. For prevention, there are two vaccines: one indicated only for people who have already been infected, the other effective against different serotypes of the virus, the use of which must, however, be evaluated on a case-by-case basis.

West Nile: Birds are the reservoirs of the virus

Unlike the other two infections, it is not the tiger mosquito that transmits the West Nile virus, but the Culex type. Also in this case there is no human-to-human transmission and the 'viral reservoirs' are mainly birds. Longer - in relation to the other two arbroviruses - is the incubation period after the bite, as symptoms can occur up to 14 days later and can even take up to 21 days in people with an immune system deficiency. Most infected persons do not develop symptoms, but if they do occur, for about 20% of those infected it is a mild form: fever, headache, nausea, vomiting, enlarged lymph nodes, skin rashes. Eighty per cent are asymptomatic and only one per cent of cases risk aggravation due to age and already compromised health conditions. The most serious symptoms may be high fever, severe headaches, muscle weakness, disorientation, tremors, impaired vision, numbness, convulsions, up to paralysis and coma. Some neurological effects may be permanent. In severe cases, the virus can cause fatal encephalitis and there is no specific treatment.

For all viruses, the main rule is to prevent infection

Whatever the name of the virus or the mosquito vector, prevention remains the most effective weapon to prevent contagion. Here are the experts' recommendations: use mosquito repellents, wear clothes that cover the body, sleep under mosquito nets, and if possible, stay in places with air conditioning or mosquito nets on the windows. It is also important to eliminate mosquito breeding places, such as stagnant water (planters and paddling pools), and to talk to your doctor about vaccination prevention, especially if you plan to travel to endemic areas.