Yellow Fever

Yellow Fever is a viral infection that spreads through mosquitoes. A person develops symptoms within about 5 days of being bitten by an infected mosquito. In the initial stage, symptoms can range from headache, joint pain, nausea and jaundice. After a brief period of remission, these symptoms might recur. The intoxication or toxic stage is the dangerous stage where there is multiple-organ failure. There can be bleeding disorder, hemorrhage, delirium and arrhythmia. Yellow fever can be prevented with a vaccination. Travelers going to locations where they are likely to be infected by mosquitoes must take precautions.

Chikungunya

Chikungunya is a viral disease caused by the chikungunya virus (CHIKV), which belongs to the genus Alphavirus, family Togaviridae. The disease was first identified in 1953 in Tanzania and is named after the Makonde language, where "chikungunya" roughly translates to "to walk bent" or "to carry a child" due to its characteristic symptoms of joint pain and swelling.

Epidemiology:
Chikungunya is primarily spread by the bite of infected mosquitoes of the Aedes genus, particularly Aedes albopictus (Asian tiger mosquito) and Aedes aegypti. The virus is endemic in Africa, Asia, and the Indian subcontinent, but outbreaks have also been reported in Central and South America, as well as the Caribbean.
Typically these mosquitoes are infected due to feeding on infected humans, monkeys or other animals. It however does not get transmitted among people. Daytime mosquitoes are the main carriers.
Transmission occurs when an infected mosquito bites a human host, and then the virus replicates in the mosquito's body before being transmitted to another individual through a subsequent bite. The incubation period is typically 2-7 days, during which time the person may experience no symptoms or mild ones. Once symptoms appear, they can persist for several weeks.

Clinical Features:
The majority of individuals infected with CHIKV will develop symptoms within 1-3 days after being bitten by an infected mosquito. The clinical presentation varies in severity but typically includes:

1. Fever: A high-grade fever (>38 degree C) that may be accompanied by sweating, chills, and rigors.
   
2. Joint pain and swelling: This is the most characteristic symptom of chikungunya, often described as intense, burning, and debilitating pain in multiple joints (hands, feet, ankles, knees, elbows, and wrists). Swelling and inflammation are common.
   
3. Rash: A pink or maculopapular rash may appear on the skin, particularly on the trunk and limbs.
   
4. Headache: Mild to moderate headache is a frequent complaint.
   
5. Muscle pain: Generalized muscle ache and stiffness can occur.
   
6. Eye involvement: Conjunctivitis (pink eye) or uveitis (inflammation of the iris or retina) may develop in some cases.
   

In rare instances, chikungunya can lead to more severe complications, such as:
1. Neurological symptoms: Encephalitis (inflammation of the brain), meningoencephalitis (inflammation of the membranes surrounding the brain and spinal cord), or Guillain-BarrΘ syndrome (a type of autoimmune neuropathy).
2. Cardiac issues: Congestive heart failure, arrhythmias, or myocardial infarction (heart attack) have been reported in some cases.

Diagnosis of chikungunya :
A diagnosis of chikungunya is typically made through a combination of clinical evaluation and laboratory testing. The following methods are used:
1. Clinical features: A careful history and physical examination can help identify the characteristic symptoms.
2. Laboratory tests:
Serological tests (ELISA or IgM/IgG antibodies) to detect CHIKV-specific antibodies in blood or serum.
Molecular detection (RT-PCR, PCR, or whole-genome sequencing) to identify the virus in blood, urine, or cerebrospinal fluid.

Treatment and Management :
There is no specific antiviral treatment for chikungunya. Supportive care focuses on managing symptoms and preventing complications. Treatment options include:
1. Pain management: Nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin, ibuprofen, or naproxen can help alleviate joint pain.
2. Rest and hydration: Patients are advised to rest, avoid strenuous activities, and maintain adequate fluid intake to prevent dehydration.
3. Physical therapy: Gentle exercises and physical therapy may be recommended to maintain joint mobility and reduce stiffness.

Prevention of chikungunya:
Preventing mosquito bites is the most effective way to avoid contracting chikungunya. Strategies for prevention include:
1. Wear protective clothing: Cover exposed skin with light-colored, loose-fitting clothing and a hat.
2. Use insect repellent: Apply insect repellents containing DEET (20-30%), picaridin, or oil of lemon eucalyptus to exposed skin and clothing.
3. Eliminate breeding sites: Remove standing water around homes and neighborhoods to prevent mosquito populations from growing.

Vaccination:
Several chikungunya vaccines are currently in development, with some having received approval for use in specific countries. The most advanced vaccine candidate is the Sanofi-Pasteur recombinant vaccine, which has shown promising results in clinical trials.