What is ... Chikungunya disease?
Chikungunya is a viral disease transmitted to people by mosquitoes.
How dangerous is Chikungunya?
Chikungunya disease does not often result in death, but the symptoms can be severe and disabling.
Most patients feel better within a week. In some people, joint pain may persist for months.
Who is at risk?
In endemic countries (see below), all people exposed to mosquitos carrying the virus are at risk.
People at risk for more severe disease include newborns infected around the time of birth, older adults ≥65 years, and people with medical conditions such as high blood pressure, diabetes, or heart disease.
How many people are affected by Chikungunya?
Millions of people living or traveling in endemic countries (see below) are at risk to acquire the disease by the bite of an infected mosquito.
Where is Chikungunya found?
Outbreaks of Chikungunya have occurred in over 60 countries in Africa, Asia, Europe, and the Indian and Pacific Oceans.
In late 2013, the first local transmission of chikungunya virus in the Americas was identified in Caribbean countries and territories.
Since then, local transmission has been identified in 45 countries or territories throughout the Americas with more than 1.7 million suspected cases reported to the Pan American Health Organization from affected areas.
SYMPTOMS AND COURSE
What are the signs and symptoms of Chikungunya?
Symptoms of Chikungunya usually begin three to seven days after being bitten by an infected mosquito.
The most common symptoms are fever and joint pain. Joint symptoms are usually bilateral and symmetric, and can be severe and debilitating.
Other symptoms may include headache, muscle pain, joint swelling, or rash.
These symptoms are similar to those of Dengue and Zika, diseases spread by the same mosquitoes that transmit Chikungunya.
How is the disease developing?
Chikungunya is characterized by an abrupt onset of fever frequently accompanied by joint pain.
Other common signs and symptoms include muscle pain, headache, nausea, fatigue and rash.
The joint pain is often very debilitating, but usually lasts for a few days or may be prolonged to weeks. Hence the virus can cause acute, subacute or chronic disease.
Most patients recover fully, but in some cases joint pain may persist for several months, or even years.
Once a person has been infected, he or she is likely to be protected from future infections.
DIAGNOSIS AND TREATMENT
How is Chikungunya diagnosed?
Chikungunya is diagnosed by performing blood tests to look for Chikungunya viruses.
More in-depth information:
Laboratory diagnosis is generally accomplished by testing serum or plasma to detect virus, viral nucleic acid, or virus-specific immunoglobulin (Ig) M and neutralizing antibodies. Viral culture may detect virus in the first 3 days of illness; however, chikungunya virus should be handled under biosafety level (BSL) 3 conditions. During the first 8 days of illness, chikungunya viral RNA can often be identified in serum. Chikungunya virus antibodies normally develop toward the end of the first week of illness. Therefore, to definitively rule out the diagnosis, convalescent-phase samples should be obtained from patients whose acute-phase samples test negative.
PREVENTION, CONTROL AND EDUCATION
How can I prevent infection?
There is no vaccine to prevent or medicine to treat Chikungunya virus infection.
The most effective way to avoid Chikungunya virus infection is to prevent mosquito bites.
The mosquitoes that spread the Chikungunya virus bite during the day and at night.
- Use insect repellent in strict accordance with product label instructions. Repellents should contain DEET, IR3535 or icaridin.
- Wear long sleeves and pants, and stay in places with air conditioning or that use window and door screens.
- Treat items, such as boots, pants, socks, and tents, with permethrin or buy permethrin-treated clothing and gear.
- Dress your child in clothing that covers arms and legs.
- Cover crib, stroller, and baby carrier with mosquito netting.
- Use screens on windows and doors.
- Repair holes in screens to keep mosquitoes outside.
- Use air conditioning when available.
- Sleep under a mosquito net
- Because mosquitoes lay eggs near water, empty and scrub, turn over, cover, or throw out items that hold water, such as tires, buckets, planters, toys, pools, birdbaths, flowerpots, or trash containers once a week.
TRANSMISSION, VECTOR AND VECTOR CONTROL
How is Chikungunya transmitted?
Chikungunya virus is primarily transmitted to humans through the bites of infected mosquitoes, predominantly Aedes aegypti and Aedes albopictus.
Humans are the primary host of chikungunya virus during epidemic periods.
Whereas Ae. aegypti is confined within the tropics and sub-tropics, Ae. albopictus also occurs in temperate and even cold temperate regions. In recent decades Ae. albopictus has spread from Asia to become established in areas of Africa, Europe and the Americas.
The species Ae. albopictus thrives in a wider range of water-filled breeding sites than Ae. aegypti, including coconut husks, cocoa pods, bamboo stumps, tree holes and rock pools, in addition to artificial containers such as vehicle tyres and saucers beneath plant pots.
Ae. aegypti is more closely associated with human habitation and uses indoor breeding sites, including flower vases, water storage vessels and concrete water tanks in bathrooms, as well as the same artificial outdoor habitats as Ae. albopictus.
In Africa several other mosquito vectors have been implicated in disease transmission, including species of the A. furcifer-taylori group and A. luteocephalus.
There is evidence that some animals, including non-primates, rodents, birds and small mammals, may act as reservoirs.
How can the vector be controlled?
The proximity of mosquito vector breeding sites to human habitation is a significant risk factor for Chikungunya as well as for other diseases that these species transmit.
Prevention and control relies heavily on reducing the number of natural and artificial water-filled container habitats that support breeding of the mosquitoes.
During outbreaks, insecticides may be sprayed to kill flying mosquitoes, applied to surfaces in and around containers where the mosquitoes land, and used to treat water in containers to kill the immature larvae.
What are the difficulties and challenges in combating Chikungunya?
The proximity of mosquito vector breeding sites to human habitation is a significant risk factor for Chikungunya as well as for other diseases that these species transmit.
It is very difficult to control or eliminate Ae. aegypti mosquitoes because of adaptations to the environment that make them highly resilient. Additionally they have the ability to rapidly bounce back to initial numbers after natural phenomena like droughts or human control measures.
One such adaptation is the ability of the eggs to withstand desiccation (drying) and to survive without water for several months. If, for instance, all larvae, pupae, and adult Ae. aegypti were eliminated at once from a site, its population could recover two weeks later as a result of egg hatching following rainfall or the addition of water to containers harboring eggs.
Ae.aegypti seem to continually adapt to environmental change. For example, it was recently found that Ae. aegypti is able to undergo immature development in broken or open septic tanks, resulting in the production of hundreds or thousands of Ae.aegypti adults per day.
In general, it is expected that control interventions will change the spatial and temporal dispersal of Ae. aegypti and perhaps the pattern of habitat utilization.
For these reasons, entomological studies should be included to give support before and throughout vector control operations.
Aedes albopictus, a secondary Chikungunya vector, has spread to North America and more than 25 countries in the European Region, largely due to the international trade in used tires, which are a breeding habitat, and other goods e.g. lucky bamboo.
Ae. albopictus is highly adaptive and, therefore, can survive in cooler temperate regions of Europe. Its spread is due to its tolerance to temperatures below freezing, hibernation, and ability to shelter in microhabitats.
INITIATIVES AND PARTNERS
What programs exist against Chikungunya?
WHO responds to Chikungunya by:
- formulating evidence-based outbreak management plans
- providing technical support and guidance to countries for the effective management of cases and outbreaks
- supporting countries to improve their reporting systems
- providing training on clinical management, diagnosis and vector control at the regional level with some of its collaborating centers
- publishing guidelines and handbooks on case management and vector control for Member States
- encouraging countries to develop and maintain the capacity to detect and confirm cases, manage patients and implement social communication strategies to reduce the presence of the mosquito vectors
What does Bayer contribute to the fight against Chikungunya?
Bayer has been successfully developing vector control products for decades (see below).
- Currently, the two most relevant Vector Control methods for fighting Chikungunya outbreak are Space Spray applications and breeding sites management. Bayer is a major supplier of Space Spray products since decades.
- A major issue is the build-up of mosquito resistance to the different active ingredient they have been exposed to. Most products used since many years are now facing this situation.
During the last six years Bayer researchers have developed an innovative approach for fighting resistance build-up. They are bringing to market a range of mosquito insecticides that combine two different modes of action, In particular, the new Fludora™ Co-Max Space Spray includes also a new chemistry family. This solution will associate robustness to resistance build up as well as excellent efficacy.
- Thanks to an innovative polymere formulation, Bayer has also launched a totally new type of intervention, Targeted Outdoor Residual Spray (TORS) . This type of application rolled out is South East Asia id particularly adapted to urban environment where Chikungunya, dengue and Zika strive. The product is marketed under the brand KOthrne™ Polyzone.
- Additionally Bayer has devised an education tool – Mosquito Control Learning Lab – an online learning platform that explains which diseases are transmitted by mosquitos, how they spread and how individuals can protect themselves against mosquito bites. The platform is interactive, testing users in their knowledge and skills in real life scenarios.
Bayer Mosquito Control Learning Lab can be accessed on any computer or tablet and is found here: https://www.environmentalscience.bayer.ph/Fight-Dengue
Besides this Bayer can look back on products that are still supplied in many parts of the world where resistance to pyrethroid insecticides is not yet established:
- Since 1990s: Aqua K-Othrine™ and Aqua Reslin™ Super are launched. These are the first space sprays to employ a new technology, Film Forming Aqueous Spray Technology (FFAST), and are used to combat adult mosquitoes in flight outdoors without releasing volatile hydrocarbons.
- Since 2015: DeltaGard™ launched in the United States. The space spray can be used at 80 times lower doses than comparable products. DeltaGard™ is currently the only product in its class that does not contain volatile organic compounds (VOCs) and is water-based. It was awarded the rarely conferred reduced-risk product classification by the U.S. Environmental Protection Agency (EPA).
What is the societal burden of Chikungunya?
In January 2016 Danielle Bloch Yale University published her article
The Cost And Burden Of Chikungunya In The Americas
in which she wrote:
Accounting for underreporting, we estimated a total of over 39.9 million cases in the Americas, imposing a burden of over 23.8 million disability adjusted life years (DALYs) lost and about US$185 billion from a societal perspective. Burden and cost varied substantially by region, with the Caribbean accounting for nearly half of the entire disease burden and costs. Over 90% of DALYs and 95% of costs were attributable to chronic inflammatory rheumatism.
In 2015 Cardona-Ospina, Villamil-Gómez, Jimenez-Canizales, Castañeda-Hernández, and Rodríguez-Morales published their article
Estimating the burden of disease and the economic cost attributable to chikungunya, Colombia, 2014
in which they wrote:
There were a total of 106 592 cases, with incidence rates ranging from 0 to 1837.3 cases/100 000 population in different departments. An estimate was made of total DALYs lost of 40.44 to 45.14 lost/100 000 population. The 2014 outbreak estimated costs were at least US$73.6 million.
Our estimates raise concerns about the effects of continued CHIK spread in Colombia and other Latin-American countries. The lack of transmission control for this disease and potential for spread means that there will be significant acute and chronic disability and related costs in the short and long term for Latin American health care systems.
In 2010 Donald S. Shepard of the Brandeis University, Waltham, MA., USA in Dengue Bulletin – Volume 34 published his article
Cost and burden of dengue and chikungunya from the Americas to Asia
where he wrote:
The ten studies in this special issue document the substantial and growing burden of dengue in the Americas, Africa and Asia, and the burden of a chikungunya outbreak in India. Luiz Tadeu Moraes Figuedo’s paper on dengue in Brazil confirms the country’s worsening trend from 1999–2009, where cases rose at 6.2% per year and dengue deaths at 12.0% per year. Carmen Perez and co-workers, reporting on dengue vector control in Puerto Rico, found that 83% of the costs (US$ 1.97 per person per year) were funded by the lowest and often the least financed level of government: municipalities. Examining dengue cases imported into France, Guy LaRuche documented the alarming increase in cases originating from Cote d’Ivoire from only one case in 2006–07 to six cases in 2008. Using modeling and Monte Carlo simulations, Tiina Murtola and co-authors estimated the “immediate” cost of chikungunya and dengue in India at US$ 1.48 billion (range US$ 0.64 billion to US$ 3.60 billion). Tapasvi Puwar and co-workers, reporting on a 2006 household survey in Ahmedabad, found that only 23% of chikungunya cases sought care in public facilities, so that under-reporting must be considerable. Extending the analysis of this chikungunyua outbreak, Dileep Mavalankar and co-authors placed its economic cost at US$ 8.6-US$ 17.3 million. Ami T. Bhavsar and co-authors, studying dengue cases hospitalized at a private hospital in Surat, India, found that the economic cost of a case averaged US$ 585.57 (US$ 439.44 for direct medical costs and US$ 146.13 for indirect costs). Lee Han Lim and coworkers, estimated the “immediate” cost of dengue to Malaysia and Thailand at US$ 133 to $135 million, respectively. Sukhontha Kongsin and co-authors found that on a per capita basis, costs of dengue in Thailand in 2005 averaged US$ 3.55, of which 28% was due to vector control and 72% due to dengue illness. Examining the burden of dengue on households in Cambodia, Jose A Suaya and co-authors found that and 53% needed to sell household property to fund dengue treatment. Effective methods to prevent the disease would, therefore, result in important economic benefits in many tropical countries.
How did the history of the disease proceed?
Chikungunya is a mosquito-borne viral disease first described during an outbreak in southern Tanzania in 1952.
It is an RNA virus that belongs to the alphavirus genus of the family Togaviridae. The name “chikungunya” derives from a word in the Kimakonde language, meaning “to become contorted”, and describes the stooped appearance of sufferers with joint pain (arthralgia).
Chikungunya occurs in Africa, Asia and the Indian subcontinent.
Human infections in Africa have been at relatively low levels for a number of years.
In 1999–2000 there was a large outbreak in the Democratic Republic of the Congo.
In February 2005 a major outbreak of chikungunya occurred in islands of the Indian Ocean.
In 2006 a large number of imported cases in Europe were associated with this outbreak.
In 2006 and 2007 a large outbreak of chikungunya occurred in India. Several other countries in South-East Asia were also affected.
Since 2005, India, Indonesia, Maldives, Myanmar and Thailand have reported over 1.9 million cases.
In 2007 there was an outbreak in Gabon.
In 2007 transmission was reported for the first time in Europe, in a localized outbreak in north-eastern Italy. There were 197 cases recorded during this outbreak and it confirmed that mosquito-borne outbreaks by Ae. Albopictus are plausible in Europe.
In December 2013, France reported 2 laboratory-confirmed autochthonous cases in the French part of the Caribbean island of St Martin.
Since then, local transmission has been confirmed in over 43 countries and territories in the WHO Region of the Americas. This is the first documented outbreak of chikungunya with autochthonous transmission in the Americas.
As of April 2015, over 1 379 788 suspected cases of Chikungunya have been recorded in the Caribbean islands, Latin American countries, and the United States of America. 191 deaths have also been attributed to this disease during the same period. Canada, Mexico and USA have also recorded imported cases.
On 21 October 2014, France confirmed 4 cases of locally-acquired chikungunya infection in Montpellier, France.
In late 2014, outbreaks were reported in the Pacific islands. In 2015 a chikungunya outbreak took place in Cook Islands and Marshall Islands, while the number of cases in American Samoa, French Polynesia, Kiribati and Samoa has reduced. Also in 2015 WHO responded to small outbreaks of chikungunya in the city of Dakar, Senegal, and the state of Punjab, India.
Again in 2015 in the Americas 693 489 suspected cases and 37480 confirmed cases of chikungunya were reported to the Pan American Health Organization (PAHO) regional office, of which Colombia bore the biggest burden with 356 079 suspected cases. This was less than in 2014 when more than 1 million suspected cases were reported in the same region.
In 2016 there was a total of 349 936 suspected and 146 914 laboratory confirmed cases reported to the PAHO regional office, half the burden compared to the previous year. Countries reporting most cases were Brazil (265 000 suspected cases), Bolivia and Colombia (19 000 suspected cases, respectively).
2016 is the first time that autochthonous transmission of chikungunya was reported in Argentina following an outbreak of more than 1 000 suspected cases. In the African region, Kenya reported an outbreak of chikungunya resulting in more than 1 700 suspected cases.
In 2017, Pakistan continues to respond to an outbreak which started in 2016.