Question

what is yellow fever

mode of transmission

sign and symtoms

diagnosis

treatment

complication

prevention

conclusion

Answer 1

Yellow Fever

Yellow fever is a viral infection spread by a particular type of mosquito. The infection is most common in areas of Africa and South America, affecting travelers to and residents of those areas.

In mild cases, yellow fever causes 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.

There'sno specific treatment for yellow fever. But getting a yellow fever vaccine before traveling to an area in which the virus is known to exist can protect you from the disease.

Causes:

Yellow fever is caused by a virus that is spread by the Aedes aegypti mosquito. 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.

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.

Mode of transmission:

The yellow fever virus is an arbovirus of the flavivirus genus and is transmitted by mosquitoes, belonging to the Aedes and Haemogogus species. The different mosquito species live in different habitats - some breed around houses (domestic), others in the jungle (wild), and some in both habitats (semi-domestic).

3 types of transmission cycles:

1. Sylvatic (or jungle) yellow fever: In tropical rainforests, monkeys, which are the primary reservoir of yellow fever, are bitten by wild mosquitoes of the Aedes and Haemogogus species, which pass the virus on to other monkeys. Occasionally humans working or travelling in the forest are bitten by infected mosquitoes and develop yellow fever.
2. Intermediate yellow fever: In this type of transmission, semi-domestic mosquitoes (those that breed both in the wild and around households) infect both monkeys and people. Increased contact between people and infected mosquitoes leads to increased transmission and many separate villages in an area can develop outbreaks at the same time. This is the most common type of outbreak in Africa.
3. Urban yellow fever: Large epidemics occur when infected people introduce the virus into heavily populated areas with high density of Aedes aegypti mosquitoes and where most people have little or no immunity, due to lack of vaccination or prior exposure to yellow fever. In these conditions, infected mosquitoes transmit the virus from person to person.

Signs And Symptoms:

During the first three to six days after you've contracted yellow fever — the incubation period — you won't experience any signs or symptoms. After this, the infection enters an acute phase and then, in some cases, a toxic phase that can be life-threatening.

Acute phase:

Once the infection enters the acute phase, you may experience signs and symptoms including:

• Fever
• Headache
• Muscle aches, particularly in your back and knees
• Sensitivity to light
• Nausea, vomiting or both
• Loss of appetite
• Dizziness
• Red eyes, face or tongue

These signs and symptoms usually improve and are gone within several days.

Toxic phase:

Although signs and symptoms may disappear for a day or two following the acute phase, some people with acute yellow fever then enter a toxic phase. During the toxic phase, acute signs and symptoms return and more-severe and life-threatening ones also appear. These can include:

• Yellowing of your skin and the whites of your eyes (jaundice)
• Abdominal pain and vomiting, sometimes of blood
• Decreased urination
• Bleeding from your nose, mouth and eyes
• Slow heart rate (bradycardia)
• Liver and kidney failure
• Brain dysfunction, including delirium, seizures and coma

The toxic phase of yellow fever can be fatal.

Diagnosis and Test

Diagnosing yellow fever based on signs and symptoms can be difficult because early in its course, the infection can be easily confused with malaria, typhoid, dengue fever and other viral hemorrhagic fevers.

To diagnose your condition, your doctor will likely:

• Ask questions about your medical and travel history
• Collect a blood sample for testing

If you have yellow fever, your blood may reveal the virus itself. If not, blood tests also can detect antibodies and other substances specific to the virus.

Complications:

Yellow Fever results in death for 20 to 50 percent of those who develop severe disease. Complications during the toxic phase of a yellow fever infection include kidney and liver failure, jaundice, Delirium, and coma.

People who survive the infection recover gradually over a period of several weeks to months, usually without significant organ damage. During this time a person may experience fatigue and jaundice. Other complications include secondary bacterial infections, such as Pneumonia infections.

Treatments and Prevention:

No antiviral medications have proved helpful in treating yellow Fever. As a result, treatment consists primarily of supportive care in a hospital. This includes providing fluids and oxygen, maintaining adequate blood pressure, replacing blood loss, providing dialysis for kidney failure, and treating any other infections that develop. Some people receive transfusions of plasma to replace blood proteins that improve clotting.

If you have yellow fever, your doctor will likely recommend that you stay inside, away from mosquitoes, to avoid transmitting the disease to others. Once you've have yellow fever, you'll be immune to the disease for the rest of your life.

Lifestyle And Home Remedies:

A safe and highly effective vaccine prevents yellow fever. Yellow Fever is known to be present in sub-Saharan Africa and parts of South America. If you live in one of these areas, talk to your doctor about whether you need the yellow fever vaccine. If you plan to travel in these areas, talk with your doctor at least 10 days, but preferably three to four weeks, before your trip begins. Some countries require travelers to present a valid certificate of immunization upon entry.

A single dose of the yellow fever vaccine provides protection for at least 10 years. Side effects are usually mild, lasting five to 10 days, and may include headaches, low-grade fevers, muscle pain, fatigue and soreness at the site of injection. More-significant reactions — such as developing a syndrome similar to actual yellow Fever, inflammation of the brain (Encephalitis) or deathcdeath can occur, most often in infants and older adults. The vaccine is considered safest for those between the ages of 9 months and 60 years.

Talk to your doctor about whether the yellow fever vaccine is appropriate if your child is younger than 9 months, if you have a weakened immune system (immunocompromised), or if you're older than 60 years.

Mosquito protection

In addition to getting the vaccine, you can help protect yourself against yellow fever by protecting yourself against mosquitoes.

To reduce your exposure to mosquitoes:

• Avoid unnecessary outdoor activity when mosquitoes are most active.
• Wear long-sleeved shirts and long pants when you go into mosquito-infested areas.
• Stay in air-conditioned or well-screened housing.
• If your accommodations don't have good window screens or air-conditioning, use bed nets. Nets that have been pre-treated with insecticide offer additional protection.

To ward off mosquitoes with repellent, use both of the following:

• Nonskin repellent. Apply permethrin-containing mosquito repellent to your clothing, shoes, camping gear and bed netting. You can buy some articles of clothing and gear pre-treated with permethrin. Permethrin is not intended for use on your skin.

• Skin repellent. Products with the active ingredients DEET, IR3535 or picaridin provide long-lasting skin protection. Choose the concentration based on the hours of protection you need. In general, higher concentrations last longer.

  Keep in mind that chemical repellents can be toxic, and use only the amount needed for the time you'll be outdoors. Don't use DEET on the hands of young children or on infants under 2 months of age. Instead, cover your infant's stroller or playpen with mosquito netting when outside.

According to the Centers for Disease Control and Prevention, oil of lemon eucalyptus, a more natural product, offers the same protection as DEET when used in similar concentrations. But these products should not be used on children younger than age 3.