AMG BRIEFING NOTE
Chikungunya (CHIKV) was detected for the first time in the western hemisphere in December 2013 and has since swept across the Caribbean causing increasing sickness and economic disruption. More than 13,180 people across the Americas have been infected, with an additional 739,400 suspected cases. Here’s what you should know.
CHIKV is caused by a virus belonging to the alphavirus genus of the family Togaviridae and is made up of a single strand of RNA (rather than the familiar DNA double helix). This means it’s able to replicate inside human and mosquito cells and causes sickness by corrupting their regular DNA. CHIKV is genetically similar to Ross River Virus (RRV) and O’nyong’nyong virus (ONNV) and has been diagnosed in almost 40 countries mainly in tropical and subtropical regions across the world.
It resembles dengue fever in that it has similar clinical features and is transmitted by mosquitoes; however it belongs to a different genus of viruses. There are four different types of dengue fever meaning that a person would need to become infected by all four types before they develop immunity, whereas only one type of Chikungunya is currently known. It is possible for a person to be infected with both dengue fever and CHIKV at the same time.
The word Chikungunya originates from the Kimakonde language spoken in Tanzania and northern Mozambique and translates as “to become distorted,” referring to the pain people feel when suffering the disease.
It was first detected in 1952 on the border between Mozambique and Tanzania and most likely originated in Central or East Africa. The virus may have arrived in Latin American and the Caribbean with travellers who had become infected in other regions or by mosquitoes arriving with imported goods.
The majority of people infected with CHIKV go on to develop symptoms within 3-7 days. The most common signs and symptoms include;
- Sudden high fever
- Joint pain and swelling – primarily in the wrists, knees, ankles and small joints
- Muscle pain
- Enlarged lymph glands
CHIKV is rarely fatal and is far less likely than dengue fever to cause complications such as hemorrhagic fever. The distinction between the two viruses is important as proper clinical management of dengue can improve the patient’s outcome. Newborn babies, people over the age of 65 and those with existing medical conditions such as diabetes and high blood pressure are at greater risk of developing complications.
It is possible to diagnose CHIKV through a range of different types of blood tests depending on the stage of infection. Practically, in many healthcare settings this isn’t always possible or deemed necessary, which is one explanation as to why the number of suspected cases is often far greater than those confirmed. Without laboratory confirmation CHIKV is often misdiagnosed as dengue.
The main vectors for CHIKV in the Caribbean are two types of mosquito called Aedes aegypti and Aedes albopictus. The mosquito first bites and feeds on an infected person who is able to transmit the disease within their first few days of infection. After an average of 10 days, CHIKV makes its way to the salivary glands of the mosquito where it is injected into another person as the mosquito feeds again.
Aedes aegypti and Aedes albopictus are the same species of mosquito that transmit dengue fever and bite mainly in the day time. In rare cases the virus can pass from mother to baby around the time of birth, although direct person-to-person transmission doesn’t happen in any other way. The virus is not airborne and cannot be transmitted through skin-to-skin or sexual contact.
Infected individuals can introduce CHIKV into receptive areas, like Latin America and the Caribbean, as most people are not immune and can become infected. Those people continue to transmit the virus to other people through the mosquito vector. There is evidence that in some parts of the world the reservoir harboring CHIKV has included non-primates, rodents, birds and small mammals.
There is no medication or vaccine for CHIKV. Advice for those who believe they are infected is to rest, drink plenty of fluids to avoid dehydration and to take medication such as paracetamol to relieve fever and pain.
What can be done to prevent CHIKV?
There is no cure or vaccine for CHIKV. There are, however, a number of things that can be done to control the outbreak and protect against infection.
- Clear away mosquito breeding sites by draining areas of still water near residential areas and removing standing buckets or vases of water from the home.
- Avoid mosquito bites by using insect repellants, wearing clothing that covers arms and legs and sleeping under mosquito nets.
- People with CHIKV should take extra precautions to avoid being bitten for the first days after the onset of symptoms as they are infectious to mosquitoes during this period.
Mosquito facts & Epidemiological terminology
- Over 3,000 mosquito species in the world
- Found on all continents apart from Antarctica
- Only female mosquitoes transmit CHIKV, dengue and malaria
- Males live five to seven days while females can live several months
- Don’t fly more than a mile from where they hatch
- Reservoir – A host of an infectious disease that often doesn’t experience symptoms
- Incubation – The period of time between infection and the onset of symptoms
- Vector – An organism that transmits a disease from one animal or plant to another
- Suspected CHIKV case – Patient with sudden fever >38°C (101°F) and severe joint pain not explained by other medical conditions, and who resides or has visited epidemic or endemic areas within two weeks prior the onset of the symptoms
- Confirmed CHIKV case – A suspected case with any specific CHIKV test
- Epidemic – A widespread occurrence of an infectious disease in a community at a particular time
- Endemic – A disease or infection regularly found among particular people or in a certain area
Although rarely fatal, CHIKV could have serious consequences for small island states. The full extent it has had – and continues to have – on the economy due to worker absenteeism is yet to be determined. Oneil Grant, Head of the Civil Service Association in Jamaica, estimates that approximately 20 percent of the public sector labour force has been affected in the country. The epidemic also underscores the vulnerability of small island states to external shocks, like epidemic disease.
|Rank||Country||Number of cases||Incidence Rate per 100,000|
|3||Saint Martin (French part)||4,240||793||5,033||14102|
|8||US Virgin Islands||902||55||957||911|
|9||Sint Maarten (Dutch part)||0||360||360||900|
|10||Antigua and Barbuda||679||18||697||774|
|13||Saint Vincent and the Grenadines||329||67||396||385|
|17||Saint Kitts and Nevis||31||28||59||116|
|19||British Virgin Islands||0||20||20||63|
|22||Turks and Caicos Islands||0||10||10||21|
|28||Trinidad and Tobago||0||43||43||3|
Number of reported cases of Chikungunya fever in the Caribbean 2013-2014
Updated October 10th, 2014 by CARPHA