Outbreak of Yellow Fever declared in Uganda.

On 6 March 2022, the World Health Organization received notification from the Uganda Ministry of Health of four suspected yellow fever cases, according to a press release. As of 25 April 2022, a total of seven suspected cases tested positive for yellow fever antibodies by plaque reduction neutralization test. However, further investigations identified only one laboratory confirmed case of yellow fever reported from Wakiso district, Central Region. The Ministry of Health declared an outbreak, and a rapid response team was deployed to the affected districts. Due to the potential of epidemic spread in Uganda and the risk of spread to neighboring countries, the World Health Organization assesses the risk to be high at the national and regional levels.

Cases presented with symptoms including fever, vomiting, nausea, diarrhoea, intense fatigue, anorexia, abdominal pain, chest pain, muscle pain, headache, and sore throat. None of the cases presented with severe yellow fever symptoms of acute jaundice. Six of the seven cases were female.

Yellow Fever is a Flavivirus (the group of RNA Viruses that also includes the West Nile, Zika and Hepatitis C Viruses) transmitted to humans by the bites of infected Aedes and Haemagogus Mosquitoes.. The Virus causes a mild fever, accompanied loss of apatite, nausea and muscle pains, which passes within about 15 days. However, in about 15 % of cases a more severe infection attacks the liver and kidneys, which can lead to their failure, and therefore the death of the patient.  It originated in tropical Africa and but was carried to South America and the Caribbean during the trans-Atlantic slave trade. Outbreaks of the disease have also been recorded in parts of tropical Asia and the Pacific in recent years, and many countries in tropical regions require visitors to carry a certificate proving they have been vaccinated against the Virus.

 

The Yellow Fever Virus. Erskine Palmer/Centers for Disease Control and Prevention/Wikipedia.

Forty countries globally, 27 in Africa and 13 in Central and South America are classified as high-risk for yellow fever. Since September 2021, 13 countries in the World Health Organization African Region have reported probable and confirmed yellow fever cases and outbreaks, including an ongoing outbreak under close investigation in neighbouring Kenya. These outbreaks are occurring in large geographic areas of the Western, Central and Eastern regions of Africa. They have affected areas that have previously conducted large-scale mass vaccination campaigns but with persistent and growing gaps in immunity due to lack of sustained population immunity through routine immunization and/or secondary to population movements (newcomers without history of vaccination). These reports indicate a resurgence and intensified transmission of the yellow fever virus.

After the Uganda Ministry of Health declared a yellow fever outbreak in the country they activated the Public Health Emergency Operation center. They are also deploying a rapid response team to affected districts where all cases were reported to determine the extent of the outbreak, identify the at-risk population, conduct a risk assessment, initiate risk communication and community engagement activities and implement integrated vector control measures.

Yellow fever vaccine has not been introduced into the Uganda routine immunization schedule; however, the country has an imminent plan to introduce it in mid-2022, followed by phased mass vaccination campaigns. Pending the evolution of the situation and response planning, a request maybe submitted to the International Coordinating Group on Vaccine Provision for preventive yellow fever vaccination in areas as indicated by ongoing investigations.

Uganda is endemic for yellow fever and is classified as a high-risk country in the Eliminate Yellow Fever Epidemics (EYE) Strategy. The country has history of outbreaks reported in 2020 (Buliisa, Maracha and Moyo districts), 2019 (Masaka and Koboko districts), 2016 (Masaka, Rukungiri, and Kalangala districts) and in 2010 when ten districts were affected in Northern Uganda.

The confirmed case is reported from Wakiso District, close to the greater Kampala metropolitan area. The district also includes Entebbe, where the international airport is located.

Uganda has not introduced the yellow fever vaccine into routine immunization and the estimated overall population immunity is low (4.2%), and attributable to past reactive vaccination activities supported by International Coordinating Group in focal districts including Yumbe, Moyo, Buliisa, Maracha, Koboko, Masaka, and Koboko, in limited scope in the Greater Kampala area, Masaka, Rukungiri, and Kalangala districts.

Epidemic spread of yellow fever is a risk in Uganda as there could be onward amplification if the virus is introduced in crowded urban areas that are known hubs for travel. There is the risk for further amplification and international spread because of frequent population movements (e.g., between Uganda, Democratic Republic of Congo and South Sudan), coupled with the low population immunity in some neighbouring countries.

The recurrent outbreaks indicate the ongoing risk of zoonotic spill over of yellow fever and risk for disease amplification in both rural and densely settled urban areas in the largely unimmunized population. Despite the yellow fever vaccine being highly effective (99% effective within 30 days of vaccination), the risk of breakthrough cases exists.  These cases should be investigated to identify and address possible causes of vaccine failure.

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Yellow Fever reported in Senegal.

The World Health Organization has reported an outbreak of Yellow Fever in Senegal, West Africa, with seven cases reported since October 2020. The first case, in a 40-year-old female patient from Kidira in the east of the country, was reported on 18 October, and confirmed by tests carried out at the Institut Pasteur de Dakar on 29 October. On 31 October an eight-year-old boy, also from Kidira, was also reported to have contracted the Virus and subsequently died of the disease. On 5 November a second death occurred in Kidira, this time a 23-year-old patient. A fourth case, this time in a fifteen-year-old male patient, was reported from Kidira on 16 November. A further three cases have been reported in Matam, Tambacounda and Kedougou, although no further fatalities have been reported.

Senegal, West Africa. Google Maps.

Yellow Fever is a Mosquito-born Flavivirus (the group of RNA Viruses that also includes the West Nile, Zika and Hepatitis C Viruses). The Virus causes a mild fever, accompanied loss of apatite, nausea and muscle pains, which passes within about 15 days. However, in about 15 % of cases a more severe infection attacks the liver and kidneys, which can lead to their failure, and therefore the death of the patient.  It originated in tropical Africa and but was carried to South America and the Caribbean during the trans-Atlantic slave trade. Outbreaks of the disease have also been recorded in parts of tropical Asia and the Pacific in recent years, and many countries in tropical regions require visitors to carry a certificate proving they have been vaccinated against the Virus.

The Yellow Fever Virus. Erskine Palmer/Centers for Disease Control and Prevention/Wikipedia.

Senegal has caried out a national program of vaccinations against Yellow Fever since 2005, however the country, particularly the eastern regions, is still considered to be a high risk for the disease, due to the persistence of the disease in wild Primates, and there are concerns that the vaccination program may have been disrupted this year by the Covid-19 epidemic.

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Outbreak of Yellow Fever in Nigeria.

The World Health Organization has reported an outbreak of Yellow Fever, which has hit five states in Nigeria. The first case of sickness was reported in the Ute Okpu Community in the Ika North-East local government area of Delta State on 24 July, with the patient dying on the 28th. By 10 November 2020, at total of 65 cases had been reported in the state, with 33 fatalities, with death typically occurring a week after the first syptoms were reported, and being proceded by fever, vomiting (with or without blood), bleeding, seizures, and unconsciousness. The patients, who are mostly from farming communities, were tested for Yellow Fever, Lassa Fever and  Severe Acute Respiratory Syndrome Coronavirus 2, though all tested negative for the latter two conditions. In Early Novermber the first of a cluster of deaths was recorded in Enugu State, where 10 of 13 cases have died; patients here were tested for Yellow Fever, Lassa Fever, Cerebrospinal Meningitis and  Severe Acute Respiratory Syndrome Coronavirus 2, and again tested negative for all diseases other than Yellow Fever. The disease has now also been confirmed in Bauchi State, where eight patients have tested positive since 8 November, though no fatalities have been recorded,  Benue State, where three cases have been reported, and Ebonyi State, where is a single case has been reported.

 

Geographic distribution of affected states and local government areas in Nigeria. World Health Organization.

Yellow Fever is a Mosquito-born Flavivirus (the group of RNA Viruses that also includes the West Nile, Zika and Hepatitis C Viruses). The Virus causes a mild fever, accompanied loss of apatite, nausea and muscle pains, which passes within about 15 days. However, in about 15 % of cases a more severe infection attacks the liver and kidneys, which can lead to their failure, and therefore the death of the patient.  It originated in tropical Africa and but was carried to South America and the Caribbean during the trans-Atlantic slave trade. Outbreaks of the disease have also been recorded in parts of tropical Asia and the Pacific in recent years, and many countries in tropical regions require visitors to carry a certificate proving they have been vaccinated against the Virus.

The Yellow Fever Virus. Erskine Palmer/Centers for Disease Control and Prevention/Wikipedia.

Yellow fever can be prevented through vaccination, but uptake of this is considered to be dangerously low in Nigeria.  To this end the Nigerian Federal Ministry of Health and World Health Organisation have initiated a program to encourage immunisation within the country, with around 54% of the country vaccinated between 2004 and 2019. There are currently 30 million doses of the vaccine available in Nigeria, with Delta and Bauchi states among those been targetted for the next phase of immunisation. 

Yellow Fever re-emerged in Nigeria in 2017, with cases subsequently reported in all 36 states and the Federal Capital Territory. The World Health Organisation regards Nigeria as a high risk country for Yellow Fever, as the disease is able to spread epizotically (in wildlife), with Human infections being essentially a spillover from an unseen epidemic.

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Seven cofirmed deaths from Yellow Fever in northern Nigeria.

Seven people have been confirmed dead in an outbreak of Yellow Fever in northeastern Nigeria, according to the Nigeria Centre for Disease Control. The first death occurred in late August 2019, when a father and son arrived at a health centre in Kano showing symptoms of the disease. Both were given immediate treatment, but the father died of the infection, and the illness was later confirmed to be Yellow Fever by the Kano State Epidemiology Team. Six further deaths form the disease were reported among students at the Waka College of Education in Borno. All of the deceased are reported to have visited the Yankari National Park in Bauchi State, where they are thought to have contracted the Mosquito-born disease, with the father and son having visited the park as part of a family excursion, and the students having been part of a group of 95 students from the college that took part in an educational trip to the park, eight of whom subsequently developed Yellow Fever symptoms. Two other people are reportedly being treated for the disease after visiting the Yankari National Park, one of whom is described as a foreign tourist.

A health worker administering Yellow Fever innoculations in Nigeria. WHO.

Yellow Fever is a Mosquito-born Flavivirus (the group of RNA Viruses that also includes the West Nile, Zika and Hepatitis C Viruses). The Virus causes a mild fever, accompanied loss of apatite, nausea and muscle pains, which passes within about 15 days. However, in about 15 % of cases a more severe infection attacks the liver and kidneys, which can lead to their failure, and therefore the death of the patient.  It originated in tropical Africa and but was carried to South America and the Caribbean during the trans-Atlantic slave trade. Outbreaks of the disease have also been recorded in parts of tropical Asia and the Pacific in recent years, and many countries in tropical regions require visitors to carry a certificate proving they have been vaccinated against the Virus.

 The Yellow Fever Virus. Erskine Palmer/Centers for Disease Control and Prevention/Wikipedia.

Yellow fever can be prevented through vaccination, but uptake of this is considered to be dangerously low in Nigeria.  To this end the Nigerian Federal Ministry of Health and World Health Organisation have initiated a program to encourage immunisation within the country, with 8.7 million adults and children vaccinated in 2018, and plans to vaccinate a further 39.5 million by the end of 2019.

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Yellow fever outbreak kills 237 in Brazil.

A total of 237 people have been confirmed dead in an outbreak of Yellow Fever in Brazil which began in July 2017. A further 468 people have been infected by the disease, including ten foreign nationals visiting Brazil (three from Argentina, three from Chile and one each from France, the Netherlands, Romania and Switzerland). The majority of the infections, and fatalities, have been reported from densely populated urban areas of Minas Gerais, São Paulo, Rio de Janeiro, and Espírito Santo states in southern Brazil, where the disease is not usually present and vaccination is not widespread. It is thought that the disease has spread to this area, along with the Aedes Mosquitoes that carry it, due to unusually hot and wet weather in the region, which favours the spread of the disease. In addition to the Human cases, 4161 cases of the disease have been reported in non-Human Primates, although only 554 of these have been confirmed by laboratory tests. Yellow Fever is thought to present a particular threat to the (often endangered) Monkey populations of Espírito Santo and Minas Gerais states, which are not familiar with the disease and which appear to be particularly vulnerable to it.

 A Howler Monkey, Alouatta sp., killed by Yellow Fever in Brazil. Sergio Mendes/Projeto Muriqui.

  

Yellow Fever is a Mosquito-born Flavivirus (the group of RNA Viruses that also includes the West Nile, Zika and Hepatitis C Viruses), that originated in tropical Africa and appears to have been carried to South America and the Caribbean during the transAtlantic slave trade. Outbreaks of the disease have also been recorded in parts of tropical Asia and the Pacific in recent years, and many countries in tropical regions require visitors to carry a certificate proving they have been vaccinated against the Virus.

The Yellow Fever Virus. Erskine Palmer/Centers for Disease Control and Prevention/Wikipedia.

The Virus causes a mild fever, accompanied loss of apatite, nausea and muscle pains, which passes within about 15 days. However, in about 15 % of cases a more severe infection attacks the liver and kidneys, which can lead to their failure, and therefore the death of the patient.

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