Important fact
Symptoms of yellow fever include fever, headache, jaundice, muscle aches, nausea, vomiting, and fatigue.
A small percentage of patients infected with the virus will develop severe symptoms, and nearly half of them die within 7-10 days.
The virus is endemic in Africa and tropical regions of Central and South America.
A pandemic can occur if infected people bring the virus into densely populated areas where many people are almost or not immune to vaccination and where mosquito density is high. In this case, the infected mosquito spreads the virus from person to person.
Yellow fever can be prevented by a very effective vaccine, and the vaccine is safe and reasonably priced. A dose of yellow fever vaccine is sufficient to achieve sustained immunity and lifelong protection without the need for continuation of the vaccine. After vaccination, 80%-100% of people get effective immunity within 10 days, and more than 99% get effective immunity within 30 days.
Providing good supportive care in the hospital can improve survival. There are currently no specific antiviral drugs for yellow fever.
The Elimination of Yellow Fever Epidemic Strategy launched in 2017 is an unprecedented major initiative. The Strategic Partnership involves more than 50 partners to support the prevention, detection and response to suspected cases and outbreaks of yellow fever in 40 risk countries in Africa and the Americas. The establishment of this partnership aims to protect the risk population, prevent international communication, and quickly curb the epidemic. By 2026, more than 1 billion people are expected to be protected from yellow fever.
Signs and symptoms
Once infected, the yellow fever virus lurks in the body for 3 to 6 days. Many people have no symptoms, but if symptoms occur, the most common are fever, muscle pain (especially 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 entered the second phase of toxicity when they recovered from the initial symptoms. Recurrence of fever, some body systems (usually the liver and kidneys) are affected. At this stage, the patient may have jaundice (yellow skin and eyes, the name of "yellow fever" will come from this), dark urine and abdominal pain accompanied by vomiting. The mouth, nose, eyes or stomach may bleed. Half of the patients entering the toxic phase die within 7-10 days.
diagnosis
Yellow fever is difficult to diagnose, especially in the early stages. Heavier conditions may be confused with severe malaria, leptospirosis, viral hepatitis (especially fulminant), other hemorrhagic fever, other flavivirus infections (such as dengue hemorrhagic fever), and poisoning.
Blood tests (reverse transcriptase polymerase chain reaction (RT-PCR)) can sometimes detect viruses at an early stage of the disease. In the later stages of the disease, antibodies are determined by detection (enzyme-linked immunosorbent assay (ELISA) and plaque reduction neutralization assay (PRNT)).
Risk group
Yellow fever is prevalent in 47 countries (including 34 in Africa and 13 in Central and South America) in countries or parts of the country. According to a simulation study conducted by African data sources, the burden of yellow fever during 2013 was 84,000–170,000 serious cases and 29,000–60,000 deaths.
Travelers who travel to countries with yellow fever occasionally bring the disease to countries where the disease is not available. To prevent this disease entry, many countries require proof of yellow fever vaccination before issuing a visa, especially if the traveler has or has visited a yellow fever endemic area.
In the 17th and 19th centuries, yellow fever was brought to North America and Europe, causing a large-scale epidemic that disrupted the economy and development and sometimes led to the death of large numbers of people.
propagation
Yellow fever virus is a flavivirus arbovirus that is transmitted by mosquitoes of the genus Aedes and the genus Haemophilus. Different species of mosquitoes live in different habitats - some breed around the house (home environment), some breed in the wild jungle, and some can breed in both environments (semi-home environment). There are three types of communication chains:
Forest type (or jungle type) yellow fever: In tropical rain forests, monkeys are the main host of yellow fever, and wild mosquitoes of the genus Aedes and the genus Haemophilus transmit germs between monkeys through bites. People who work or travel in the forest are occasionally bitten by infected mosquitoes and contracted with yellow fever.
Intermediate yellow fever: In this type of transmission, mosquitoes in the semi-home environment (which can breed in the wild and around the house) infect monkeys and humans. More contact between humans and infected mosquitoes leads to increased viral transmission, and many isolated villages in a region may have an outbreak at the same time. This type of outbreak is most common in Africa.
Urban yellow fever: If infected people bring the virus into densely populated areas with high density of Aedes aegypti, many of these people have little or no immunity due to lack of vaccination or previous exposure to yellow fever. A pandemic will happen. In this case, the infected mosquito spreads the virus from person to person.
treatment
Providing early good supportive care in the hospital improves survival. At present, there is no specific antiviral drug for yellow fever, but the treatment of dehydration, liver and kidney failure and fever symptoms through specific nursing measures can improve the results. Antibiotics can be used to treat related bacterial infections.
prevention
Vaccination
The yellow fever vaccine is safe and reasonably priced, and a single dose of vaccine is sufficient to provide a lifetime protection against the disease without the need for continuation of the vaccine.
Several vaccination strategies have been used to prevent yellow fever and its transmission, including: routine immunization of infants; large-scale vaccination campaigns to increase coverage in risk-prone countries; and vaccination for travelers travelling to areas where yellow fever is endemic .
In high-risk areas with low vaccination coverage, timely identification and control of the epidemic through mass immunization is critical to preventing disease epidemics. To prevent transmission in areas where yellow fever outbreaks occur, most people at risk (over 80%) must be vaccinated.
There are very few reports of serious side effects caused by yellow fever vaccines. In areas where yellow fever is endemic, the incidence of serious adverse events after liver, kidney or nervous system-related immunization is 0 to 0.21 per 10,000 doses of vaccine, and 0.09 to 0.4 per 10,000 doses of vaccine in non-exposure populations. (1)
People over the age of 60 and those with severe immunodeficiency due to symptomatic HIV/AIDS or other causes, or those with thymic disorders, are at higher risk of adverse events following immunization. For those over 60 years of age, the pros and cons should be carefully weighed before vaccination.
People who are not suitable for vaccination usually include:
Infants less than 9 months old;
Pregnant women - except in the case of a yellow fever epidemic with a high risk of infection;
Those who are severely allergic to egg protein; and
People with severe immunodeficiency due to symptomatic HIV/AIDS or other causes, or people with thymic disorders.
According to the International Health Regulations, the State has the right to require travellers to provide proof of vaccination against yellow fever. If the vaccine cannot be vaccinated for physical reasons, it must be certified by the relevant authorities. The International Health Regulations are a legally binding framework designed to stop the spread of infectious diseases and other health threats. It is up to each State Party to decide whether or not to require travellers to provide vaccination certificates. Not all countries currently require proof.
2. Vector control
The risk of yellow fever transmission can be reduced by removing potential mosquito breeding sites, including spraying larvae in water storage containers and other locations with stagnant water.
Vector monitoring and control is an integral part of the prevention and control of vector-borne diseases, especially the control of epidemics. In the prevention and control of yellow fever, monitoring vectors such as Aedes aegypti and other Aedes mosquitoes can help to understand which cities are at risk of an outbreak.
Understanding the distribution of these mosquitoes in the local area will help the country identify areas where disease surveillance and detection and disease vector control actions need to be strengthened. At present, from the perspective of public health and safety, due to the resistance of the main vector to common insecticides and the withdrawal or abandonment of certain pesticides for reasons such as safety or re-registration of high costs, the effective use of adult vectors can be used. Cost-effective pesticides are limited.
Historically, the anti-mosquito campaign has succeeded in eliminating Aedes aegypti, a medium of urban yellow fever, in most parts of Central and South America. However, this mosquito is now re-emerging in urban areas of the region, exacerbating the risk of resurgence of urban yellow fever. Control planning for wild mosquitoes in forest areas is not practical to prevent the spread of jungle-type (or forest-type) yellow fever.
Preventing mosquito bites suggests taking personal precautions such as reducing skin exposure and using insect repellents. Because Aedes mosquitoes usually bite during the day, the use of insecticides to treat mosquito nets has not been effective.
3. Popular prevention and response
The timely detection of yellow fever and rapid response to emergency vaccination activities is extremely important for epidemic control. However, insufficient reporting is a matter of concern. The actual number of cases is estimated to be 10 to 250 times the number of cases reported today.
WHO recommends that each country with an infection risk establish at least one national laboratory for basic yellow fever blood testing. An outbreak can be considered if a confirmed case of yellow fever occurs in an unvaccinated population. In any case, if a confirmed case occurs, a thorough investigation must be conducted. The investigation team must evaluate the outbreak and take urgent measures to establish a longer-term immunization plan.
WHO response
In 2016, two related yellow fever urban outbreaks occurred in Luanda (Angola) and Kinshasa (Democratic Republic of the Congo) and international spread from Angola to other countries including China. This suggests that yellow fever poses a serious threat on a global scale and requires new strategic thinking. The “Strategy for Eliminating Yellow Fever Outbreak” was developed to address the increased threat of yellow fever urban outbreaks and international spread. Under the guidance of WHO, UNICEF and the Global Alliance for Vaccines and Immunization, the Yellow Fever Elimination Strategy supports 40 countries and involves more than 50 partners.
The Strategy for Eliminating the Yellow Fever Outbreak is guided by the following three strategic objectives:
Protecting risk groups;
Prevent the international spread of yellow fever;
Quickly curb the epidemic.
To achieve these goals, we need the following five aspects of capacity support:
Affordable vaccines and sustainable vaccine markets;
Strong political commitment at the global, regional and national levels;
High-level governance and long-term cooperation;
Collaborate with other health programmes and departments;
Research and develop better tools and practices.
The Strategy for Eliminating the Yellow Fever Epidemic is a comprehensive strategy of diversity and multi-partners. In addition to the proposed vaccination campaign, the strategy also calls for the establishment of resilient urban health centres, planning for urban preparedness and strengthening the implementation of the International Health Regulations (2005).
The Partnership for Eliminating the Yellow Fever Outbreak Strategy supports yellow fever and high-risk countries in Africa and the Americas by strengthening their monitoring and laboratory capabilities to respond to yellow fever cases and outbreaks. Strategic partners strongly support the implementation and sustainability of routine immunization programmes and vaccination campaigns (preventive, early priority, reactive) whenever and wherever.
To ensure a rapid and effective response to the epidemic, the 6 million doses of the yellow fever vaccine emergency reserve funded by the Global Alliance for Vaccines and Immunization is continuously being supplemented. The contingency reserve is managed by WHO as the secretariat's International Coordination Group for Vaccine Supply.
Hello, my name is Abdullah Waseem. I'm a 21 year old self-employed from the Pakistan.
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