What is Yellow Fever? Promoting awareness in Ghana

On 4^th June, 2016, the Ghana Health Service reported four confirmed cases of yellow fever in the country: three cases in Brong-Ahafo region and one case in Volta region. A press release by the Director General of the service, Dr. Ebenezer Appiah-Denkyira, stated there is no need to panic since the 2011 vaccination exercise has provided most people with immunity against the disease [1].

This short article seeks to educate the public about Yellow Fever, common signs and symptoms, preventive measures and treatment for the disease.

Yellow Fever is a viral disease characterized by rapid onset of severe symptoms that may disappear within 3 to 4 days. The common symptoms include fever chills, loss of appetite, nausea, headache, tiredness and muscle pain [3]. The second phase of the disease, the toxic phase, may be accompanied by jaundice due to liver damage, abdominal pain, bleeding in the mouth, nose and eyes, and bloody vomit [3, 4]. Patients who enter the second phase are likely to die within 7 – 10 days [3].

Yellow Fever is caused by a virus that belongs to the family Flaviviridae. The disease is mainly transmitted by infected mosquitoes and its origin is traced to West Africa [2]. Tropical and subtropical areas are mostly prone to the disease.

The transmission of yellow fever occurs through three types of transmission cycles: 1) sylvatic or wild, 2). intermediate and 3) urban cycles [3]. The first cycle mainly occurs among monkeys in tropical rainforests, which are the primary host of yellow fever. Wild mosquitoes transmit the disease to other monkeys after biting infected monkeys. Humans who visit the forest may become infected when bitten by infected wild mosquitoes. The intermediate cycle involves transmission among animals and humans by mosquitoes that breed both in the wild and around households. In densely populated human settlements (i.e. urban areas), yellow fever transmission occurs among humans via infected anthropophilic mosquitoes such as Aedes aegypti [5].

When an infected mosquito bites a human, the yellow fever virus enters the bloodstream and invade the vessels of the lymphatic system. The viruses settle in the lymph nodes where they multiply and infect antigen-presenting cells (particularly dendritic cells) [6]. When liver cells are infected by the viruses, the liver may be damaged leading to jaundice.

Yellow fever can be prevented through routine vaccination of people living in endemic areas. About 99% of the people administrated with the vaccine acquire protection within 30 days [3]. It is highly recommended for people travelling to affected areas to get yellow fever vaccination. Severe symptoms are commonly reported among non-natives of affected areas.

The spread of yellow fever can be controlled by taking measures that will reduce breeding of the yellow fever mosquitoes (i.e. the Aedes species). They are likely to breed in areas with accumulated water. Treated mosquito nets and treated paints (such as inesfly paint products) are recommended for households to prevent mosquito bites.

Currently, there is no cure for yellow fever disease. Infected patients are normally hospitalized and treated with drugs for fever, dehydration, pain and liver failure [8]. Yellow Fever can be very deadly and preventive measures, including vaccination and control of mosquitoes, must be taken in affected areas.

References

1. Ghana News – Yellow Fever strikes in Brong Ahafo, Volta regions [Internet]. [Cited 2016 Jun 18]. Available from: http://www.myjoyonline.com/news/2016/June-4th/yellow-fever-strikes-in-brong-ahafo-volta-regions.php
2. Cliff, A., Haggett, P. and Smallman-Raynor M. (2004). World Atlas of Epidemic Diseases. Arnold London.
3. WHO | Yellow fever [Internet]. WHO. [Cited 2016 Jun 18]. Available from:http://www.who.int/mediacentre/factsheets/fs100/en/
4. Monath TP. Yellow fever: an update. The Lancet Infectious Diseases. 2001 Aug; 1(1):11–20.
5. Rogers DJ, Wilson AJ, Hay SI, Graham AJ. The Global Distribution of Yellow Fever and Dengue. Adv Parasitol. 2006; 62:181–220.
6. Ryan,K.,J.and Ray.C.,G.(2004).Sherris Medical Microbiology,4^th Edition, Mc-Graw Hill publications ,ISBN 0-8385-8529-9.
7. Barret, A., D.and Tenwen,D.ME.(2009). Current Opinion in immunology, Yellow fever vaccine; 21(3):308-313’
8. Tolle M., A. (2009). Cuprprobl Pediatry Adolescence Health Care, Mosquito-borne-disease; (4):97-140.

By: Bright Oppong Afranie, (BSc. Biochemistry student, KNUST)