Focus – Arbovirus

The word “arbovirus” is an acronym for “arthropod-borne virus”, which describes a virus that comes from arthropods.

More than a million different arthropods, that is more than 80 % of all described living animal species, have already been described by scientists − and there may be millions more out there. Arthropods include mosquitoes, spiders, ticks, sandflies, mites, millipedes, centipedes, crabs, lobsters, crayfish and shrimps. More than a 100 arboviruses are known.

The following arboviruses are found in Africa: West Nile, sindbis, yellow fever, dengue, chikungunya and Rift Valley.

What happens?

An arbovirus lives inside a host (eg birds or monkeys). An arthropod (eg a tick, mosquito or sandfly) feeds on the host and now carries the virus, thus becoming the vector. This vector transfers the virus to other organisms by feeding on their blood. In turn the newly infected organism now becomes a host for the virus … and thus the cycle continues. However, humans are not good hosts because arboviruses usually cannot thrive in the human body and usually humans cannot transfer the viruses to other humans.

Symptoms

The symptoms of an arbovirus infection generally occur within three to five days (but in some cases up to 15 days) after exposure to the virus and last for three to four days. The symptoms range from acute slight fevers of short duration to serious viral fevers where bleeding occurs and death. The most common symptoms of infection are fever, headache, rash and feeling unwell.

Prevention

Apart from environmental campaigns to eradicate vectors such as mosquitoes, the only way of preventing arbovirus infection is to prevent being bitten by the vectors in the first place. The following tips will help:

• • Wear clothing with long sleeves and cover your ankles – especially at dawn and dusk when mosquitoes are most active.

• • Apply insect repellents directly to the skin.

• • Use long-lasting insecticide sprays inside homes and buildings.

• • Use mosquito netting over the beds – they can also be soaked in certain types of insecticide.

• • Treat blankets and even clothing with insect repellents.

• • Place wire or gauze screens on all doors and windows.

• • Keep a fan on in the room during the night – the current seems to ward off the mosquitoes.

• • Spend evenings indoors rather than outdoors – you are much less likely to get bitten by mosquitoes.

• • Get rid of discarded tires, cans or plastic containers left outside that may contain standing water.

• • Turn over plastic wading pools and wheel barrows when not in use so that the water cannot gather in them.

• • Regularly drain standing water from your pool or hot tub cover.

• • Replace the water in bird baths, pet dishes and wading pools every three to four days.

• • Keep drains, ditches and culverts clean of trash and weeds so water will drain properly.

• • Clean the gutters to ensure they drain properly.

• • Where appropriate, get a vaccine before visiting an area where there is an arbovirus outbreak, for example of yellow fever.

 

Sources

https://en.wikipedia.org/wiki/Arbovirus
https://www.dhs.wisconsin.gov/arboviral/index.htm
http://www.medicinenet.com/script/main/art.asp?articlekey=16556
Prinsloo, B. Arboviral diseases in southern Africa. SA Fam Pract 2006:48(8).
Retrieved from http://www.safpj.co.za/index.php/safpj/article/view/665/579
Rautenbach, PGD. Mosquito-borne viral infections in southern Africa: a public health perspective. Retrieved from ttp://cmej.org.za/index.php/cmej/article/viewFile/2103/1794

A 2016 outbreak of yellow fever in some regions of Angola, has led to renewed awareness of this disease. People in southern Africa want to know if they are at risk.

Yellow fever occurs in 34 countries in Africa and also in other countries such as China, Democratic Republic of Congo (DRC) and Kenya. Namibia and Zambia remain on high alert for imported cases.

In Angola an outbreak of yellow fever occurred in December 2015 in Luanda and since then the disease has spread to six of the country’s 18 provinces where it affected 450 and killed 178 people, according to the World Health Organisation (WHO). This situation is exacerbated by the fact that there currently is a shortage of vaccine against yellow fever.

What is yellow fever?

Yellow fever is an acute viral disease that causes bleeding. Some people suffering from the disease show signs of jaundice, hence “yellow” in the name of the disease. Unfortunately almost half of affected persons will die from yellow fever if they do not receive treatment.

How is yellow fever transmitted?

The yellow fever virus is one of the viruses that are transmitted by mosquitoes. Mosquitoes of the Aedes and Haemogogus species carry the virus from one host to another, usually between monkeys, from monkeys to humans, and also from humans to humans. The mosquitoes can breed around houses or in the jungle, that is, virtually anywhere.

Symptoms of yellow fever

Yellow fever takes between three and six days to incubate and grow in the body. Then the sufferer will have symptoms such as:

• • Fever

• • Muscle pain with prominent backache

• • Headache

• • Shivers

• • Loss of appetite

• • Nausea or vomiting.

These symptoms may disappear after 3 to 4 days.

After the initial remission phase, in 15% of sufferers a second and worse phase appears within 24 hours. The symptoms of this phase include:

• • High fever

• • Rapidly developed jaundice

• • Abdominal pain

• • Vomiting

• • Bleeding from the mouth, nose, eyes or stomach

• • Blood in the vomit and faeces

• • Deteriorating kidney function.

People who recover from this phase (about 50%) will have significant organ damage.

Yellow fever is difficult to diagnose, especially during the early stages. Blood tests can confirm the diagnosis by detecting yellow fever antibodies in the body.

Should you be concerned about yellow fever?

Unfortunately people living in Africa, travelling to Africa and especially those living near areas of outbreak are at higher risk of the disease. African data sources indicate that 84000–170000 cases of severe yellow fever occurred in 2013 and from these 29000–60000 people died.

There is no specific treatment for yellow fever. Only the symptoms are treated to make the sufferer more comfortable. The best way forward is to prevent the disease in the first place.

If you have been to a yellow fever area and you feel ill, or if you think you may have yellow fever, you are advised to consult a health professional immediately. Tell this person where you’ve been, if you’ve been bitten or if you think you may have been bitten by a mosquito. Do not take aspirin or ibuprofen as this may thin your blood.

What can you do to prevent yellow fever?

The most important prevention measure is the yellow fever vaccination. The WHO recommends routine infant immunisations (starting at 9 months of age) and mass vaccination campaigns in high-risk areas for all people of 9 months and older. People travelling to areas where the disease occurs, should also have the vaccination. The vaccine provides effective immunity within 30 days in 99% of persons vaccinated.

The vaccine is safe, affordable, and highly effective. A single dose of yellow fever vaccine is sufficient to give life-long protection against yellow fever.

Other preventative measures include the preventions of mosquito bites by:

• • Covering up exposed skin by wearing long-sleeved shirts, long pants, socks, boots and hats

• • Using an appropriate insect repellent as directed.

Sources

Yellow fever. Retrieved from http://wwwnc.cdc.gov/travel/diseases/yellow-fever
Yellow fever fact sheet, March 2016. Retreived from http://www.who.int/mediacentre/factsheets/fs100/en/
Yellow fever high alert for Southern Africa. Retrieved from http://www.medicalbrief.co.za/archives/yellow-fever-high-alert-for-southern-african/