Yellow fever is a disease caused by a virus that is spread by mosquito bites. Symptoms take 3-6 days to develop and include fever, chills, headache, back pain, and muscle aches. About 15% of people who contract yellow fever develop serious illnesses that can lead to bleeding, shock, organ failure, and sometimes death. Yellow Fever
Signs and symptoms
Once infected, the yellow fever virus stays in the body for 3 to 6 days. Many people do not experience symptoms, but when they do, the most common are fever, muscle aches with significant back pain, headache, loss of appetite, and nausea or vomiting. In most cases, the symptoms disappear after 3 to 4 days.
However, a small percentage of patients enter a second, more toxic phase within 24 hours of recovery from initial symptoms. A high fever returns and many body systems are affect, most commonly the liver and kidneys. In this stage, people are likely to experience jaundice (yellowing of the skin and eyes, hence the name ‘yellow fever’), dark urine and abdominal pain with vomiting. Half of the patients who enter the toxic phase die within 7 to 10 days.
Diagnosis Of Yellow Fever
A more severe case may be confused with acute malaria, leptospirosis, viral hepatitis (especially fulminant forms), other hemorrhagic fevers, infection with other flu viruses (such as dengue hemorrhagic fever), and poisoning.
Polymerase chain reaction (PCR) tests in blood and urine can sometimes detect the virus in the early stages of the disease. In later stages, tests are need to identify antibodies (ELISA and PRNT).
Populations At Risk
47 countries in Africa (34) and Central and South America (13) are either endemic, or have areas that are endemic for yellow fever. A modeling study based on African data sources estimated that the burden of yellow fever during 2013 was 84 000–170 000 severe cases and 29 000–60 000 deaths.
Occasionally, travelers visiting endemic countries may carry the disease to yellow fever-free countries. To prevent such importation of the disease, many countries require proof of vaccination against yellow fever before issuing a visa, especially if travelers are coming from, or visiting areas endemic for yellow fever. do
In previous centuries (17th to 19th), yellow fever was transmitted to North America and Europe, causing large-scale epidemics that destroy economies, development, and in some cases populations.
Treatment Of Yellow Fever
Good and early supportive treatment in hospitals improves survival rates. There is currently no specific antiviral medication for yellow fever but specific care to treat dehydration, liver and kidney dysfunction, and fever improves outcomes.
Prevention From Yellow Fever
1. Vaccination
The yellow fever vaccine is safe, and inexpensive, and one dose provides lifelong protection against yellow fever disease.
Several vaccination strategies are used to prevent yellow fever disease and transmission: routine childhood immunization; Mass immunization campaigns design to increase coverage in high-risk countries. and vaccination of travelers to yellow fever endemic areas.
In high-risk areas where vaccination coverage is low, rapid identification and control of outbreaks using mass immunization is critical. In order to prevent the transmission of yellow fever to an endemic area, it is necessary to put a large (80% or more) population at risk.
The rate of these serious ‘adverse events after immunization (AEFI), when the vaccine attacks the liver, kidneys, or nervous system, ranges from 0 to 0.21 cases per 10 000 doses in areas where yellow fever is endemic. and 0.09 to 0.4 cases per 10 000 doses in virus-uninfected populations (1).
The risk of AEFI is higher for people over 60 years of age and those with severe immunodeficiency due to symptomatic HIV/AIDS or other causes, or who have a thymus disorder. People over 60 years of age should be vaccinate after a careful risk-benefit assessment.
Children under 9 months of age;
Pregnant women – except during jaundice outbreaks when the risk of infection is high.
People with a severe allergy to egg protein; According to the International Health Regulations (IHR), countries have the right to require travelers to provide a jaundice vaccination certificate. If there are medical grounds for non-vaccination, it must be certified by the relevant authorities. The IHR is a legally binding framework for preventing the spread of communicable diseases and other health threats. Requiring a vaccination certificate from travelers is at the discretion of each State Party, and not all countries currently require it
2. Vector control
The risk of jaundice transmission in urban areas can be reduced by eliminating potential mosquito breeding sites, including applying larvicides to water storage containers and other areas where standing water collects.
Both vector surveillance and control are components of vector-borne disease prevention and control, particularly for transmission control in epidemic situations. For jaundice vector surveillance targeting Aedes aegypti and other Aedes species will help identify where urban outbreaks are at risk.
Understanding the distribution of these mosquitoes within a country can allow a country to prioritize areas to strengthen its human disease surveillance and testing and consider vector control activities. There is currently a limit arsenal of safe, effective, and cost-effective public health insecticides that can be used against adult vectors. This is mainly due to major vector resistance to common insecticides and the withdrawal or abandonment of certain insecticides for safety reasons or the high cost of re-registration.
Historically, mosquito control campaigns have successfully eliminated Aedes aegypti, the vector of urban jaundice, from much of Central and South America. However, Aedes aegypti has recolonized urban areas in the region, raising a new risk of urban jaundice. Mosquito control programs targeting wild mosquitoes in forested areas are not practical to prevent transmission of forest (or sylvatic) jaundice
Personal protective measures such as clothing to reduce skin exposure and repellents are recommend to avoid mosquito bites. The use of insecticide-treat bed nets is limit by the fact that Aedes mosquitoes bite during the day.
3. Epidemic preparedness and response
Rapid detection of jaundice and rapid response through emergency vaccination campaigns are essential to control the outbreak. However, underreporting is a concern – the true number of cases is estimate to be 10 to 250 times higher than what is now being report.
WHO recommends that each at-risk country have at least one national laboratory where basic yellow fever blood tests can be perform. A confirmed case of jaundice in an unvaccinated population is consider an epidemic. Any confirm case should be thoroughly investigate. Investigation teams must anticipate and respond to this outbreak with both emergency measures and long-term immunization plans.