Chikungunya Virus (CHIKV)
Chikungunya is a mosquito-borne viral disease that causes symptoms such as fever and severe joint pain [1]. “The disease was first recognized in 1952 during an outbreak in southern Tanzania [1]. It is a ribonucleic acid (RNA) virus that belongs to the alphavirus genus of the family Togaviridae” [1]. Chikungunya virus is transmitted to humans by the bites of infected female mosquitoes (Aedes aegypti and Aedes albopictus) [1]. These two species of mosquitoes also transmit other mosquito-borne viruses such as dengue[1]. They bite throughout daylight hours, although there may be peaks of activity in the early morning and late afternoon [1].
CHIKV is transmitted when an uninfected mosquito feeds upon a viremic person (someone who has the virus circulating in their blood), the mosquito can pick up the virus as it ingests the blood [2][3]. The virus then undergoes a period of replication in the mosquito, which then is transmitted to a healthy human when the mosquito feeds next [3]. If a mosquito feeds on a person during the time he/she has a virus circulating in their blood, the mosquito can pick up the virus, and the transmission cycle begins again [3].
After the bite of an infected mosquito, the onset of illness usually begins 4-8 days later (but can range from 2-12 days) [2][3]. Chikungunya is characterized by an onset of fever, frequently accompanied by joint pain [3]. Other common signs and symptoms include muscle pain, joint swelling, and stiffness, headache, nausea, fatigue and rash [3]. Most people recover fully from this infection, however, the joint pain is often very debilitating; it usually lasts for a few days, but may persist for months or even years [3]. Hence, the virus can cause acute, subacute or chronic disease [3].
The infection from the Chikungunya virus may go unrecognized or may be misdiagnosed as the symptoms in infected individuals are usually mild [3]. Fortunately, unlike dengue, chikungunya rarely progresses to become life-threatening [3]. Once an individual is recovered, they are likely to be immune from future infections [3].
Although the Chikungunya virus is rarely fatal, the socioeconomic burden that comes with the massive number of people missing work and school as a result of the disease is large [2]. This society burden had been experienced in other Pacific Island countries that have dealt with the epidemic [2]. “Chikungunya outbreaks have occurred in the past in the Pacific region in New Caledonia (2011), Papua New Guinea (2012), Yap State in Micronesia (2013), and in Samoa, Tonga and Tokelau islands (since June 2014) [4]”.
Several methods can be used for the diagnosis of chikungunya virus infection:
Serological tests, such as enzyme-linked immunosorbent assays (ELISA)- may confirm the presence of IgM and IgG anti-chikungunya antibodies [3]. “IgM antibody levels are highest 3 to 5 weeks after the onset of illness and persist for about 2 months” [3].
Serological and virological methods (particularly reverse transcriptase-polymerase chain reaction (RT–PCR))- the virus may be directly detected in the blood during the first few days and can be detected in this test [3].
Unfortunately, there is no specific antiviral drug treatment for chikungunya [3]. The clinical management aims at relieving the symptoms, including the joint pain using antipyretics, optimal analgesics, drinking plenty of fluids, and taking rest [3]. Paracetamol or acetaminophen are recommended for pain relief and reducing fever [3].
Due to the similarity of symptoms between chikungunya and dengue, suspected chikungunya patients should avoid using aspirin or Non-steroidal anti-inflammatory drugs (NSAIDs) until a dengue diagnosis is ruled out [3]. In the case of dengue, these medicines can increase the risk of bleeding [3].
The proximity of mosquito vector breeding sites to the human population is a significant risk factor for chikungunya [3]. The main method to control or prevent the transmission of the chikungunya virus is to combat the mosquito vectors [3]. This relies heavily on reducing the number of water-filled container habitats that support the breeding of the mosquitoes [3].
The mobilization of affected and at-risk communities efforts are required to empty and clean containers that contain water on a weekly basis, hence serving as an effective tool in inhibiting mosquito breeding [3]. Furthermore, the Ministry encourages all individuals, government sectors, and corporate entities in Fiji to work together with the Ministry of Health in destroying mosquito breeding grounds through frequently organized clean-up campaigns [2].
For protection during outbreaks of chikungunya, clothing which minimizes skin exposure is advised [3]. “Repellents can be applied to exposed skin or to clothing in strict accordance with product label instructions [3]. Repellents should contain DEET (N, N-diethyl-3-methylbenzamidej), IR3535 (3-[N-acetyl-N-butyl]-aminopropionic acid ethyl ester) or icaridin (1-piperidinecarboxylic acid, 2-(2-hydroxyethyl)-1-methylpropylester)” [3]. Furthermore, insecticide-treated mosquito nets afford good protection for those who take naps during the day since mosquitoes that transmit chikungunya feed primarily during daylight [3].
Basic precautions should be taken by individuals traveling to or living in risk areas. These include the use of repellents, wearing long sleeves and pants, and ensuring rooms are fitted with screens to prevent mosquitoes from entering are recommended [3].
Reference
1. World Health Organization. Chikungunya Virus. Available at: https://www.who.int/health-topics/chikungunya/#tab=tab_1
2. Ministry of Health and Medical Services. Media Release. Chikungunya Alert. Riaz Hassan. 2015
3. World Health Organization. Chikungunya. Fact Sheet. 2020
4. European Centre for Disease Prevention and Control. Chikungunya in Pacific Region. 2014