Overview of Yellow Fever
Yellow fever is a viral infection caused by a flavivirus (Aedes aegypti mosquito), which is spread in Africa and South America, particularly in areas with dense forests or jungles. These mosquitoes thrive in and near human habitations where they breed in even the cleanest water. Most cases of yellow fever occur in sub-Saharan Africa and tropical South America. This is largely dependent on the climate and the presence the environment.
Humans and monkeys are most commonly infected with the yellow fever virus. Mosquitoes transmit the virus back and forth between monkeys, humans or both.
When a mosquito bites a human or a monkey infected with yellow fever, the virus enters the mosquito's bloodstream and circulates before settling in the salivary glands. When the infected mosquito bites another monkey or human, the virus then enters the host's bloodstream, where it may cause illness.
In mild cases, yellow fever causes a fever, headache, nausea and vomiting. But yellow fever can become more serious, causing heart, liver and kidney problems along with bleeding (hemorrhaging). Up to 50 percent of people with the more-severe form of yellow fever die of the disease.
However, for about 10 percent to 15 percent of those infected, it can become serious, resulting in high fever, jaundice, and other concerns. Yellow fever can be fatal.
Yellow Fever Epidemic in Nigeria
In Nigeria, yellow fever is an endemic and seasonal disease, occurring often in areas with poor sanitation, thus making its outbreaks not being unusual.
Although, issues relating to yellow fever in Nigeria haven’t been frequently reported, thus making the disease look quite dynamic in nature, yet the existence of such disease in our communities (especially rural areas) can’t be undermined.
On the 23rd of October, 1969, the virus research laboratory of the University of Ibadan, Oyo State, was notified of a suspected case of Yellow fever occurring in Jos, Plateau State; where the diagnosis was confirmed and the widespread of the disease made it to be recognized as the first epidemic case of Yellow fever in Nigeria since 1953. Between September and the end of December 1969, an estimated total of 252 patients with yellow fever were hospitalized. The case — fatality ratio for hospitalized patients was approximately 40%. The diagnosis of yellow fever was confirmed by virus isolation, serology, or pathology in 55 patients. It is estimated that up to 100,000 cases of yellow fever may have occurred during the epidemic.
After this major outbreak, Nigeria has witnessed more outbreaks in various States across the nation (2011, 2016, and 2017), more recently in five States (Bauchi, Borno, Kano, Gombe, and Katsina).
According to recent reports by the Nigeria Centre for Disease Control (NCDC) as at 18th September 2019, about 2,000 suspected yellow fever cases have been reported in Nigeria to the World Health Organization (WHO) during the year 2019.
Two hundred and forty – three (243) new cases have been reported in 42 LGAs in these five states (Bauchi (84), Borno (82), Gombe (7), Kano (4) and Katsina (66). Samples have been collected from 195 cases and total death tolls of 34 deaths have been recorded among these suspected cases (Bauchi (10), Kano (1), and Kaduna (23).
According to World Health Organisation operatives in Nigeria, there is currently a moderate risk at these affected regions level due to the possible movement of the individuals of affected States to adjacent areas and neighboring countries, particularly if there is the arrival of unvaccinated visitors to the State.
Also to combat this deadly outbreak, a 4-year national yellow fever Preventive Mass Vaccination Campaign plan is currently being implemented.
[Next Week: How Yellow Fever Presents – Signs and Symptoms]