October 21, 2021

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chikungunya fever

What is chikungunya fever and its causes?

Chikungunya fever, caused by a virus transmitted by mosquitoes, is an illness that causes an acute feverish picture. Originally from Africa, it has spread throughout Asia and the Americas.

Chikungunya fever is a disease by a virus of the same name, infected through the bite of an infected mosquito, which causes an acute febrile illness that usually resolves without complications. It was described for the first time in 1952 in Tanzania. Shortly afterward, it was discovered that it was an endemic disease in Africa (in the Makonde language – from ​​Tanzania and Mozambique – it means ‘twisting’ or ‘bending over in pain’ ). Since then, cases have been described worldwide, mainly in India and the rest of Asia.

The chikungunya virus belongs to the group of arboviruses, a type of virus transmitted by arthropod bites. It is a virus known for decades, which mainly affects tropical countries where there is no record of the number of cases. However, it is estimated that the involved people reach millions in 40 different countries in Africa and almost two million since 2013 in America, initially in the Caribbean area. In Europe, most of the cases are imported. However, some autochthonous transmission cases have been described in France, Croatia, and Italy (where there was an outbreak in the Emilia-Romagna region in 2007).

The main symptoms caused by this disease are very high fever and painful inflammation of the joints. Affected people present a significant decay, similar to the flu, which forces them to remain on bed rest for about a week. Treatment is symptomatic since there are no specific drugs to eliminate the responsible virus.

It has not been shown that it can be transmitted from person to person (except mother to fetus) but through the bite of certain mosquitoes. These mosquitoes are Aedes aegypti and Aedes albopictus, common insects in tropical and subtropical countries, and transmit other diseases such as dengue or yellow fever. The mosquito bites infected people, absorbs the virus and then spreads it to other healthy people by transmitting it to them with a bite. Preventing the bite of this mosquito is essential to avoid infection.

Since the 1950s, most cases have occurred in Africa, with small outbreaks in the rest of the world always in relation to travelers from that continent. Starting in 2004, the epidemic spread to islands in the Pacific, India, China, Southeast Asia, and Australia. Since 2013, the number of cases has multiplied, mainly due to the epidemic that has spread in the Dominican Republic (a frequent tourist destination) and other Caribbean areas. Currently, there is circulation and transmission of Chikungunya throughout Central America and in the tropical and subtropical parts of South America. There have also been cases in the United States, Italy, Spain, France, and England.

For all these reasons, chikungunya fever is already considered a global infectious disease. Despite being a pathology that most of the time does not involve serious complications, health authorities around the world are already on alert.

Causes of chikungunya fever

The person responsible for this disease is a virus, chikungunya, from the Togaviridae family. These viruses have been known for decades to cause conditions that are transmitted by arthropod bites. The chikungunya fever virus cannot be transmitted from person to person. Its contagion is always through specific types of mosquitoes, Aedes aegypti and Aedes albopictus. 

The Aedes aegypti cannot live in any climate, require climates tropical or subtropical to reproduce, so the Chikungunya fever has been limited in specific geographic regions. However, global warming is one of the causes that may contribute to its expansion and explain why the number of cases increases in other latitudes. 

The Aedes albopictus or tiger mosquito is an invasive species from Asia that is currently also found in more temperate areas on all continents (except Antarctica), extending from the east coast and southeastern states of the United States to the northern provinces from Argentina, in addition to areas of Mediterranean Europe, such as the Spanish Levantine coast. Its circular white stripes can recognize this annoying black mosquito on its legs. When some of these mosquitoes bite a person with chikungunya, the transmission cycle begins.

The tiger mosquito bites mainly during the day, and the Aedes aegypti can do it at any time, although preferably at dusk or dusk. Only the female bites because she needs human blood that favors the synthesis of sex hormones to produce eggs.