Biology and Mode of Transmission
Chikungunya is a single stranded positive sense RNA virus
that belongs to the genus Alphavirus of
the Togaviridae family. It is an arthropod virus that is transmitted to humans
primarily by Aedes aegypi and Aedea albopictus mosquito species carrying
the virus1. It typically replicates in the fibroblasts, myofibers
and premature skeletal muscle cells of its hosts an eventually travels to the
blood stream. In the event that another mosquito bites the infected individual,
they can proceed to spread the virus to that mosquito. Once the mosquito has acquired
the virus it can then go on to perpetuate the infection2.
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| Chikungunya Virus http://www.saintbarth.com/chikungunya-virus-dengue-fever-st-barts-1180/ |
Origin
The word Chikungunya was primarily thought to have been
derived from the Swahili language spoken by habitants of South East Africa, but
it originated from the Bantu language which is spoken by the people of Mozambique
and Tanzania. The word translates to “that which bends up”, which refers to the
posture infected individuals assume due to severe discomfort in their joints1.
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| Worldwide distribution of chikungunya virus http://www.nature.com/nrmicro/journal/v8/n7/fig_tab/nrmicro2368_F1.html |
Initially, people mistook the virus for malaria but in 1953,
it was first isolated from an infected host after there was an outbreak in East
Africa. Since its isolation, the virus remained endemic until it re-emerged in
Kenya and caused millions of infections in Africa, South Asia and South-East
Asia3. Of late it has been seen to have spread to unexpected parts
of the world such as the Caribbean.
Symptoms and Treatment
Chikungunya is not always symptomatic but when it is,
symptoms typically include those similar to that of dengue fever. Sudden high fever
and joint pains are usually the major symptoms that are noticed but patients
may also experience joint stiffness, muscle pain, headaches, nausea and rashes.
Most infected individuals recover within 3 – 7 days after being bitten by an
infected mosquito. Though symptoms can create severe discomfort, the mortality
rate is relatively low, ranging from 1 to 2 percent. The majority of the deaths
occur in either the elderly or individuals with compromised immune systems4.
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| Symptoms of infection include pain in the joints http://www.specialistpainphysio.com/wp-content/uploads/2012/01/arthritis-lg.jpg |
There is currently no treatment or vaccine for the chikungunya virus
but medication can be prescribed to help alleviate the symptoms.
Why is it a public health problem?
The Chikungunya virus re-emerged in 2006 in areas
surrounding the Indian Ocean, infecting more 200 000 people in the Réunion
islands and more than 1.25 million cases in and around India over a six month
period. By 2007, the virus found its way into parts of France, Germany,
Switzerland, Italy and Norway1. Upon arrival in Europe, it was made
clear that this virus was able to travel to new ecological niches outside of
Africa and India. To date at least 18 countries found in Asia, Europe and North
America have documented imported cases of the virus5.
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| A map of areas where Chikungunya occurs http://gamapserver.who.int/mapLibrary/Files/Maps/Global_Chikungunya_ITHRiskMap.png |
It has also been recently reported that there has been a
drastic increase in the quantity of chikungunya fever cases in the Caribbean, particularly
on the island of St. Martin. As of December 28, 2013, the WHO confirmed that
there were 66 known cases and 167 suspected cases in this particular location.
In addition there have also been three reported cases on the nearby island of
Martinique and one new case on the Guadeloupe. The case in Guadeloupe is the
first known case of chikungunya in the history of the country and is found to
be quite intriguing because the infected individual has reported never traveling
anywhere that the disease was prevalent6.
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| Map of the Eastern Caribbean (Note: Guadeloupe, St Martin and Dominica) http://govia.files.wordpress.com/2010/04/eastern-caribbean-composite1.jpg |
Moreover, a news article was released on February 8, 2014
confirming that there are now 13 new cases on the island of Dominica. Health
authorities in the Caribbean are extremely concerned because this is a new
virus to the area, indicating that the population may be extremely susceptible7.
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| Aedes aegypti Mosquito https://www.vectorbase.org/image-gallery/Aedes%20Species/A.%20aegypti |
The major contributing factor as to why this outbreak has received
so much attention is because this virus has never been reported to have spread
to this area of the world before. Having it now present in the Caribbean, and its
prevalence continuing to steadily increase; it poses a threat to the United States,
seeing as though infected travellers returning to the US may introduce the
virus to local Aedes aegypti and Aedes alboptictus species of mosquitoes6,7.
At this current point in time the CDC has confirmed that there are presently no
known cases of chikungunya in the United States, but public health officials
continue to remain on high alert8.
What is being done to mitigate its impact?
Health care providers in the Caribbean are being encouraged
to increase vigilance concerning potentially new cases of the diseases through
early identification in order to be aware of latent cases returning to the US,
especially during periods of increased travels7.
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| Attentive health care workers are required for early diagnosis http://www.contractorrecruiting.com/remediation-recruiting/ |
In addition, those travelling to the Caribbean are
encouraged to wear mosquito repellent and take other measure to reduce their
likelihood of being infected (i.e. using a mosquito net). Furthermore the CDC
sees it important to control the vectors at the site of breeding. These
controls would include reducing the likelihood of standing water being present for
extended periods of time after rainfall (i.e. proper disposal of tires, putting
a lid on water tanks, etc)6.
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| CDC http://facefwd.com/tag/cdc/ |
One of the major reasons why mitigating this virus is challenging
for health care workers is that the incubation period for this virus ranges
from two to 12 days. This short incubation period creates an increased
likelihood that the infected individual will be unaware that they are carrying
the disease.
In the event an individual is experiencing symptoms similar
to those of the virus, Health Canada encourages them to see a health care
provider4.
For more information refer to links below:
http://www.who.int/mediacentre/factsheets/fs327/en/
http://www.cdc.gov/chikungunya/
References
References
- Taubitz, W., Cramer, J. P., Kapaun, A., Pfeffer, M., Drosten, C., Dobler, G., ... & Löscher, T. (2007). Chikungunya fever in travelers: clinical presentation and course. Clinical Infectious Diseases, 45(1), e1-e4.
- Ozden, Simona, et al. "Human muscle satellite cells as targets of Chikungunya virus infection." PLoS One 2.6 (2007): e527.
- Staples, J. Erin, Robert F. Breiman, and Ann M. Powers. "Chikungunya fever: an epidemiological review of a re-emerging infectious disease." Clinical infectious diseases 49.6 (2009): 942-948.
- Government of Canada. Chikungunya. Travel Health and Safety. Diseases. 2014-2-7. http://travel.gc.ca/travelling/health-safety/diseases/chikungunya
- Gould, E. A., et al. "First cases of autochthonous dengue fever and chikungunya fever in France: from bad dream to reality!." Clinical microbiology and infection 16.12 (2010): 1702-1704.
- Schnirring, L. Caribbean chikungunya outbreak grows, poses threat to US. Center for Infectious Disease Research and Policy, Dec 30, 2013. http://www.cidrap.umn.edu/news-perspective/2013/12/caribbean-chikungunya-outbreak-grows-poses-threat-us
- Jamaica Observer. Dominica records increase in Chikungunya disease. Feb 8, 2014. http://www.jamaicaobserver.com/latestnews/Dominica-records-increase-in-Chikungunya-disease
- Centers for Disease Control and Prevention. Chikungunya fever. Dec 12, 2013. http://www.cdc.gov/chikungunya/
