What you need to know about yellow fever

Africa has for a long time fought an unending war with mosquitoes. Commonly known to cause the leading cause of death in Uganda, malaria, mosquitoes also transmit zika virus which makes women deliver children with smaller heads (microcephaly) and cause yellow fever in humans and monkeys.
Yellow fever is a hemorrhagic viral disease that is transmitted by mosquitoes infected with the virus. Transmission is carried from monkeys to humans and between fellow humans.

Status of Uganda
According to Dr Julius Lutwama, the head of arbovirology emerging and re-emerging viral infections at the Uganda Virus Research Institute, Uganda is one of the countries living in the yellow fever belt although it is rated at medium risk.
“We have a favourable environment and the mosquitoes that transmit the virus found in forests. However, these mosquitoes do not normally bite human beings so there are occasional outbreaks in the country despite having a high percentage of the population not immunised” Dr Lutwama explains.
Sources say ministry of Health is organising a mass vaccination campaign against yellow fever in Masaka region.

Transmission
According to Centre for Disease Prevention, mosquitoes acquire the virus by feeding on infected primates (human or non-human) and then can transmit the virus to other primates.
People infected with yellow fever virus are infectious to mosquitoes (referred to as being “viremic”) shortly before the onset of fever and up to five days after onset.
Yellow fever virus has three transmission cycles: jungle (sylvatic), inter­mediate (savannah), and urban.
CDC explains that jungle (sylvatic) cycle involves transmission of the virus between non-human primates (such as monkeys) and mosquito species found in the forest canopy. The virus is transmitted by mosquitoes from monkeys to humans when humans are visiting or working in the jungle.
The savannah cycle predominantly in Africa involves transmission of virus from mosquitoes to humans living or working in jungle border areas. In this cycle, the virus can be transmitted from monkey to human or from human to human via mosquitoes, primarily Aedes aegypti.

Treatment
Dr Lutwama says treatment of yellow fever is asymptomatic which means it is treated depending on the symptoms.
“In case a person has fever, paracentamol or panadol can be administered to help, if renal problems occur, the necessary steps should be offered,” Dr Lutwama explains.
He adds that if a patient survives to the 12th day of infection, there is a likelihood he or she will survive.
“Not everyone who gets the fever dies; 20 to 40 per cent of those who get infected die,” he says.
CDC, however, warns of administering certain medicines such as aspirin, ibrufen and other non-steroidal anti-inflammatory drugs which may increase the risk of bleeding.

Signs and symptoms
Explaining the disease, Dr Stuart Musisi the district health officer Masaka, says it is transmitted by Aedes mosquitoes which bites people during the day. The mosquitoes are usually found in jungles; the affected sub-counties are surrounded by thick forests along Lake Victoria shores.
“People who become ill usually present with rapid onset of fever that does not respond to malaria treatment. One can also develop symptoms like nausea, vomiting, kidney failure, jaundice and bleeding,” Dr Musisi says.
WHO adds that the yellow fever virus hatches in the body between three and six days before translating into infection. At the start of the infection, the person will get fever, muscle pain centered on the back, headache, shivers, loss of appetite and nausea. However, 15 per cent of the infected later on present with severe symptoms a day after the first symptoms disappear.

“High fever returns and several body systems are affected. The patient rapidly develops jaundice and complains of abdominal pain with vomiting. Bleeding can occur from the mouth, nose, eyes or stomach. Once this happens, blood appears in the vomit and faeces. Kidney function deteriorates,” WHO says.
Dr Lutwama adds that it takes four days for the symptoms to start appearing although he says it depends on different people, the climate and the amount of virus in the body. He adds yellowing of the eyes, tongue and hands as other signs of the disease. This happens due to the infection on the liver where the virus attacks; which is in advanced stages of the fever.

The patient can also present bloodshot eyes, bleeding may occur in the nose, the faeces and the urine. He also cites renal symptoms such as failure to pass urine as another probable symptom. He continues that when the bleeding and renal or kidney related symptoms start, there is a high possibility the patient will die.
WHO say it is hard to identify the fever in its early stages as it can easily be confused with severe malaria, dengue hemorrhagic fever and other fevers although blood tests can detect the yellow fever antibodies produced in response to the infection.
Centers for Disease Control (CDC), says infected people should be protected from mosquitoes since they can cause re-transmission of the disease from person to person for at least five days.

Previous attacks

This, however, is not the first fever outbreak recorded in the country. Dr Lutwama lists outbreaks in 1939 and 1940 which took place in Bundibugyo District although the magnitude was not recorded. He also cites individual case recordings in 1952, 1959, 1964 and 1971; 158 people were also reported to be infected with the fever in 2010-2011. He adds that in 1970-1971, an outbreak took place in monkeys in the Zika forest.
“Currently, the outbreak has been contained although investigations are still taking place to determine the origin of the fever. We have found out that Buwunga sub-County where the first case was recorded holds the vectors for transmission but we are still conducting more research,” Dr Lutwama shares.

Prevention

Due to the absence of a single form of treatment, vaccination is the best way to prevent infection of yellow fever, Dr Lutwama says. However, he states that Uganda at the moment has very few vaccination centres with most of them being found in private clinics.
WHO advises vaccination coverage to reach at least 60 per cent of the populations at risk for effectiveness or prevention in addition to routine infant immunization, one-time mass campaigns to increase vaccination coverage and for travelers to yellow fever endemic areas.
In 2010, Ministry of Health planned to vaccinate 2.5 million people in the northern region following a yellow fever outbreak that killed 45 people and 183 afflicted. The targeted districts were Abim, Agago, Kitgum, Lamwoo and Pader. The 2010 outbreak was the first in 40 years but was later on followed by three confirmed cases in 2011.

Dr Lutwama says currently, Ministry if Health is in the process of getting the vaccine which is in short supply because of the more urgent outbreaks in Angola and Congo.
“We usually vaccinate depending on the availability of the vaccine and the outbreaks. If we procure the vaccines this year, we will only vaccinate the surrounding areas of Buwongo where cases have been reported,” Dr Lutwama explains.
Once vaccination occurs, WHO says 90 per cent of those vaccinated will get protection within 10 days and 99 per cent within 30 days. One shot of the vaccine offers life-long protection. Experts add that serious side effects are rare.
Even though WHO offers mosquito prevention as a probable method of prevention, Dr Lutwama says it is unlikely to prevent mosquito bites or reduce the number of mosquitoes.

“It is not a sure deal to prevent mosquito bites or have complete mosquito control. All these depend on the environment but you cannot be so sure. So the only sure way to protect yourself is through vaccination.”
WHO cites epidemic preparedness and response saying countries susceptible to outbreaks or infections should be ready to carry out emergency vaccination campaigns. In addition to this, there is need to have laboratories which can carry out confirmatory tests and thorough investigations. Currently, all tests are carried out by the Uganda Virus Research Institute.
However, it adds that the number of registered cases have been decreasing since 2006 after the launch of the Yellow Fever Initiative.

Statistics
According to World Health Organisation (WHO), 800 million people living in 44 countries in Africa and Central and South America are prone to the fever. There are between 84,000 and 170, 000 cases recorded every year and up to 60 000 related deaths.
Uganda is one of the countries recording new cases. Outbreaks have been confirmed in Angola where hundreds have been reported dead and Democratic Republic of Congo where 21 deaths have so far occurred. In Uganda, more than 10 cases have been confirmed in Masaka district, 10 dead and 13 suspected cases showing signs of the fever.
According to Dr Stuart Musisi, the Masaka district health officer, the fever has spread to more sub-counties within the district surrounding Buwunga Sub-county where the first cases were recorded.

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