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A number of chikungunya outbreaks have occurred since 2005. An analysis of the chikungunya virus's genetic code suggests that the increased severity of the 2005–present outbreak may be due to a change in the genetic sequence, altering the virus' viral coat protein, which potentially allows it to multiply more easily in mosquito cells and utilise the Asian tiger mosquito (an invasive species) as a vector in addition to the more strictly tropical main vector, Aedes aegypti. In July 2006, a team analyzed the virus' RNA and determined the genetic changes that have occurred in various strains of the virus and identified those genetic sequences which led to the increased virulence of recent strains.
An outbreak was recorded on the French island of Réunion in the Indian Ocean between 28 March 2005 and 12 February 2006. 1722 cases of chikungunya were reported, but estimates reach 110,000 infected people. Other nearby countries in the southwest Indian Ocean reported cases as well, including Mauritius and the Seychelles. Cases were also reported in Madagascar, the Comoros, and Mayotte.
2006: India and Bangalore
In 2006, there was a large outbreak in India. States affected by the outbreak were Andhra Pradesh, Andaman & Nicobar Islands, Tamil Nadu, Karnataka, Maharashtra, Gujarat, Madhya Pradesh, Kerala and Delhi. The initial cases were reported from Hyderabad and Secunderabad as well as from Anantpur district as early as November and December 2005 and is continue unabated. In Hyderabad alone an average practitioner saw anywhere between 10 and 20 cases every day. Some deaths have been reported but it was thought to be due mainly to the inappropriate use of antibiotics and anti-inflammatory tablets. The major cause of mortality is due to severe dehydration, electrolyte imbalance and loss of glycemic control. Recovery is the rule except for about 3 to 5% incidence of prolonged arthritis. As this virus can cause thrombocytopenia, injudicious use of these drugs can cause erosions in the gastric epithelium leading to exsanguinating upper GI bleed (due to thrombocytopenia). Also the use of steroids for the control of joint pains and inflammation is dangerous and completely unwarranted. On average there are around 5,300 cases being treated every day. This figure is only from public sector. The figures from the private sector combined would be much higher.
There have been reports of large scale outbreak of this virus in Southern India. At least 80,000 people in Gulbarga, Tumkur, Bidar, Raichur, Bellary, Chitradurga, Davanagere, Kolar and Bijapur districts in Karnataka state are known to have been affected since December 2005.
A separate outbreak of chikungunya fever was reported from Malegaon town in Nasik district, Maharashtra state, in the first two weeks of March 2006, resulting in over 2000 cases. In Orissa state, at most 5000 cases of fever with muscle aches and headache were reported between February 27 and March 5, 2006.
In Bangalore, the state capital of Karnataka (India), there seemed to be an outbreak of chikungunya in May 2006 with arthralgia/arthritis and rashes. As well as in the neighbouring state of Andhra Pradesh. In the 3rd week of May 2006 the outbreak of chikungunya in North Karnataka was severe. All the North Karnataka districts specially Gulbarga, Koppal, Bellary, Gadag, Dharwad were affected. The people of this region are hence requested to be alert. Stagnation of water which provides fertile breeding grounds for the vector (Aedes aegypti) should be avoided. The latest outbreak is in Tamil Nadu, India - 20,000 cases have been reported in June 2006. Earlier it was found spreading mostly in the outskirts of Bangalore, but now it has started spreading in the city also (Updated 30/06/2006). More than 300,000 people are affected in Karnataka as of July 2006.
Reported on 29/06/2006, Chennai—fresh cases of this disease has been reported in local hospitals. A heavy effect has been reflected in south TN districts like Kanyakumari and Tirunelveli. Residents of Chennai are warned against the painful disease.
June 2006—Andaman Islands (India) chikungunya cases had been registered virtually for the first time in the month of June 2006. In the beginning of the September cases have gone as much as in thousands.As reported in a local news magazine it has taken the state of epidemic in Andamans. Health authorities are doing their best to handle the situation. Relapsed cases have been noticed with severe pain and swelling in the lower limbs, vomiting and general weakness.
As of August 2006, nearly 100,000 people were infected in Tamil Nadu. Chennai, capital of Tamil Nadu is one of the worst affected.
On 24 August 2006, The Hindu newspaper reported that the Indian states of Tamil Nadu, Karnataka, Andhra Pradesh, Maharashtra, Madhya Pradesh, Gujarat and Kerala had reported 1.1 million (11 lakh) cases. The government's claim of no deaths is questioned.
On 28 May 2009 in Changwat Trang of Thailand where the virus is spreading throughout many parts of the country, especially amongst the military troops in the southern region; the provincial hospital made a decision to prematurely deliver a male baby from his chikungunya-infected mother—Khwanruethai Sutmueang, 28, a Trang native—in the hopes of preventing mother-foetus virus transmission. Upon having delivered the baby by section, the physicians discovered that he has also been infected with the chikungunya virus, and put him into an intensive care. One impact of the virus is that the baby cannot breathe (respiration) on his own and cannot drink milk. The Thai physicians gave a preliminary presumption that chikungunya virus might be able to be transmitted from a mother to her foetus. However, there is no laboratory confirmation.
An outbreak occurred in Cambodia with at least 1500 confirmed cases. Provinces for which affection was confirmed were: Preah Vihear, Battambang, Kampong Thom, Kampong Chhnang, Kandal, Kampong Speu and Takeo.
2013–14: The Caribbean
In December 2013, it was confirmed that chikungunya was being locally transmitted in the Americas for the first time in the French Caribbean dependency of St. Martin, with 66 confirmed cases and suspected cases of around 181. It is the first time in the Americas that the disease has spread to humans from a population of infected mosquitoes.
By mid-January 2014, a number of cases had been confirmed in five countries: St. Martin, St. Barthelemy, Martinique, Guadeloupe, and the British Virgin Islands. At the start of April, at least ten nations had reported cases. By the start of May, there were more than 4,100 probable cases, and 31,000 suspected cases spanning 14 countries, including French Guiana, the only non-island nation with at least one reported case. On May 1, the Caribbean Public Health Agency (CARPHA) declared a Caribbean-wide epidemic of the virus.
As of 21 January 2014, no cases had been reported in Puerto Rico. But by 15 July 2014, over 400 cases had been reported and health authorities believed the number of actual cases (i.e., including unreported cases) was much higher. By November 2014 the Pan American Health Organization reported about 800,000 suspected Chikungunya cases in the Caribbean alone. 
2014: United States
On July 17, 2014, the first chikungunya case acquired in the United States was reported in Florida by the Centers for Disease Control and Prevention in a man who had not recently traveled outside the United States. Shortly after another case was reported of a person in Florida being infected by the virus, not having traveled outside the U.S.
These were the first two cases where the virus was passed directly by mosquitoes to persons on the U.S. mainland. Aside from the locally acquired infections, there were 484 other cases reported in the United States as of 5 August 2014.
In September 2014, Health Minister Nancy Pérez stated that only 400 Venezuelans were infected with Chikungunya while the Central University of Venezuela stated that there could be between 65,000 and 117,000 Venezuelans infected. The Venezuelan government has announced a three stage plan to counter the outbreak, with Health Minister Pérez stating that the key function is to eliminate areas of mosquito breeding.
2014: Costa Rica
As of December 2014, Costa Rica had 47 reported cases of Chikungunya. 40 of these originated abroad, while 7 were locally acquired.
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