JIDC is introducing a new section of our Blog, Outbreaks. Outbreaks will report on current infectious outbreaks worldwide and will include a summary of scientific information and /or epidemiology concerning the pathogen. If you have an outbreak to report or a summary you would like to see posted, please contact me at email@example.com.
Outbreak: Chikungunya Outbreak in the Republic of Congo
Chikungunya fever is a crippling disease caused by an arthropod-borne virus (arbovirus) transmitted to humans through mosquitoes. Although Chikungunya virus is not often associated with mortality, the effects of virus outbreaks are often devastating, causing significant economic loss. The recent outbreak of Chikungunya fever in the Republic of Congo has reported thousands of people affected.
Outbreak of Chikungunya in the Republic of Congo
It was reported by IRIN, the UN’s humanitarian news and analysis service, on June 15th, 2011 that a large outbreak of possible Chikungunya fever (CHIKF) is affecting the Republic of Congo (http://www.irinnews.org/Report.aspx?ReportID=92989). In Brazzaville, the Republic of Congo’s largest city, an estimated 1,000 cases of CHIKF is suspected since the beginning of June. CHIKF in humans is caused by infection of the chikungunya virus (CHIKV) which is transmitted by mosquitoes to people (arbovirus). Testing of patients who presented with CHIKF symptoms in the Republic of Congo have resulted positive for the CHIKV.
IRIN reported “More than 900 people are showing symptoms of chikungunya, which is transmitted by mosquito,” Director-General of Health Alexis Elira Dokekias told a news conference on 14 June.
By the end of June (June 28, 2011) an IRIN representative reported there were approximately 8,000 CHIKF affected people with no associated deaths.
Although historically CHIKV is found in tropical regions of the globe, outbreaks have been reported in temperate regions suggesting the expanding tropism of the virus.
JIDC and CHIKV
JIDC has published 3 articles on CHIKV that can be found Open Access on the JIDC website:
- A Review of Chikungunya by Cavrini F. et al., JIDC 2009 entitled Chikungunya: an emerging and spreading arthropod-borne viral disease .
- Antiviral therapy for Chikungunya by Ravichandran R. and Manian M. JIDC 2008 entitled Ribavirin therapy for Chikungunya arthritis .
- A Case Report of Chikungunya in India by Kumari R. et al., JIDC 2010 entitled The first Chikungunya case from Sonipat district near the national capital city of Delhi, India.
CHIKF not only a disease of the tropics
Historically CHIKV was only found in tropical regions. In 2007, an outbreak of CHIKV occurred in Emilia Romagna region of Northern Italy. The Italian outbreak of CHIKV spread through communities surrounding the city of Ravenna during August to October 2007 and also involved the major Italian city of Bologna [5,6]. In Italy, 254 people were determined to be infected with CHIKV which was transmitted by Ae. albopictus mosquito. The mosquito has been found in the Emilia Romagna region since 1990 [7–9]. The virus was brought to the Emilia Romagna region by a traveller returning from a CHIKV affected country. The virus was of the Central/East African virus genotype [7,8]. Genomic sequencing showed that the amino acids sequence included a substitution mutation in the E1 envelope protein (E1-A226V)  which is important for viral entry into host cells. This mutation was acquired during the large 2005-2006 Indian Ocean CHIKV outbreak and enabled the virus to infect the Ae. albopictus mosquito where previously it only infected the Ae. aegyptii . Importantly, from this outbreak, it was shown that temperate regions are also susceptible to the CHIKV infections and not only tropical regions.
CHIKV Outbreak in Emilia Romagna region of Northern Italy. Cavrini F. et al., JIDC 2009
History of CHIKV
Interestingly, CHIKV has been shown to infect and be transmitted by 2 species of mosquitoes: Ae. aegyptii and Ae. albopictus mosquitoes. Chikungunya was identified in East Africa in the early 1950s and since then has caused epidemics in continental Africa, the Indian Ocean region, and countries of Southeast Asia such as India where there has been an estimated 1.39 million cases (since 2006) [4,12–15] . The only reported outbreak outside of these areas was in Italy in the Emilia Romagna region in 2007. Small non-epidemic imported cases have been reported in other regions such as North America, France and Japan which were caused by travellers returning from affected areas [16–18].
The epidemic which occurred on La Reunion Island, Indian Ocean in 2005-2006 was a devastating CHIKV outbreak where over one-third of the population was affected . During this outbreak, the CHIKV acquired a genetic mutation permiting the Ae. albopictus mosquito to carry the CHIKV. Previously CHIKV only circulated in Ae. aegyptii mosquitoes [19,20]. CHIKV is now of global health concern since expansion of mosquito vectors has created potential for the Chikungunya virus to spread to temperate areas as Ae. albopitcus inhabits regions in North America and Europe [21,22].
CHIKV Clinical Manifestations
The defining symptom of CHIKF is severe joint pain and as the severe joint pain increases the patient often takes a bent posture. Chikungunya, a word originating from the Tanzanian and Mozambique region meaning that which bends up, describes this distorted posture. Other symptoms of CHIKF include sudden appearance of high fever, rash, headache, nausea, vomiting, myalgia and arthalgia or severe joint pain. Symptoms start 4 to 7 days following infection which defines the acute phase of CHIKF. Importantly, the acute phase lasts approximately 2 weeks, joint pain can persist for months or years following initial infection [6,7,23].
CHIKV Immune Response and Treatments
Currently, the immune response for CHIKV infection remains largely uninvestigated and there is no specific treatment available. Reported in 2010, Ravichandran R. and Manian M. investigated the use of the antiviral agent ribavirin in patients suffering from severe joint pain attributed to CHIKV infection . The ribavirin treated patients had a faster resolution of joint pain and joint inflammation compared to a control patient group.
Cytokines have also been investigated as possible therapeutic drug targets and or biomarkers for CHIKF [24,25]. Importantly, Cytokines are immune mediators that direct immune responses during infection. Ng and colleagues found that IL-1b, IL-6 and RANTES were correlated with severe acute phase CHIKF during the Singapore 2007 CHIKV outbreak . Recently it was reported the acute phase of CHIKV infection is characterized by a strong innate immune response leading to CD8 T cell adaptive immunity. It is clear that the immune response toward CHIKV needs to be further investigation and the cytokine signatures validated as possible biomarkers and/or drug targets for CHIKF.
Chikungunya Virus Phylogenetics
Chikungunya virus (CHIKV) is a single-stranded positive-sense RNA virus where there are three genotypes transmitted by mosquitoes. The virus is of the Alphavirus genus in the Togaviridae family [21,23].
Thanks to the IRIN!
Do you have questions? Or would you like to report and outbreak in your area? Please contact JIDC and let us know! firstname.lastname@example.org
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2. Cavrini F, Gaibani P, Pierro AM, Rossini G, Landini MP, Sambri V (2009) Chikungunya: an emerging and spreading arthropod-borne viral disease. J Infect Dev Ctries 3: 744-752.
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