Chikungunya

Chikungunya is a viral infection that affects millions of people every year.

It is caused by the chikungunya virus. This disease is a major global health concern. It spreads rapidly across many different geographic regions. The virus is found mainly in tropical and subtropical areas. These warm climates support large populations of mosquitoes. These mosquitoes act as the primary vectors for the disease.

The virus moves between humans through specific mosquito species. The two main carriers are Aedes aegypti and Aedes albopictus. These mosquitoes typically bite during the day. They are most active around dawn and in the late afternoon.

When a mosquito bites an infected human, it picks up the virus. The virus then replicates inside the mosquito without harming it. When that mosquito bites another person, the virus is introduced into their body. The virus can also circulate among animals like birds and rodents. It may even pass from a mother to her child during birth.

Once the virus enters the body, it follows a specific biological path. The mosquito's bite breaks the skin and releases the virus. The virus first replicates in cells near the bite site. It then enters the lymphatic system and the bloodstream. From there, it circulates to various organs and tissues. The virus often reproduces in the spleen and the lymphatic system. It also targets muscles, tendons, and peripheral joints. In severe cases, the virus can even infect the liver or the brain. During the acute phase, large amounts of the virus are in the blood. This makes it very easy for new mosquitoes to become infected.

Symptoms usually appear three to seven days after the initial bite. This early period is known as the acute phase. Many people experience a sudden high fever. This fever is often accompanied by severe muscle and joint pain. This pain is often symmetric, meaning it affects both sides of the body. For example, if one elbow is painful, the other elbow usually is too. Some patients describe this pain as "excruciating." About half of the infected people also develop a skin rash. This rash can cover a small area or more than 90% of the skin. Other symptoms include headaches, nausea, fatigue, and eye sensitivity.

Most people recover from the acute phase within one week. However, the disease can move into a chronic stage. Between 30% and 40% of people continue to have symptoms after the first week. These lasting symptoms usually involve joint pain, arthritis, or swelling. This chronic pain can last for months or even several years. In rare cases, the virus causes serious neurological issues. These can include inflammation of the brain or the myelin sheaths around neurons. The mortality rate is low, at fewer than 1 in 1,000 symptomatic cases. Most deaths occur in people with pre-existing health conditions.

Scientists first identified the virus in 1952 in Tanzania. The name comes from Makonde words meaning "to become contorted." This name describes how the pain affects a person's movement. Since the 2000s, the disease has spread to many new areas. It is now considered endemic in many parts of the world.

Doctors diagnose the infection by testing blood samples. They look for viral RNA or antibodies. They must be careful because symptoms look like dengue or Zika fever. These other diseases are also spread by Aedes mosquitoes. Testing requires sophisticated laboratory equipment to be accurate.

There is currently no specific medical treatment to cure chikungunya. Doctors instead provide supportive care to manage symptoms. This includes rest, fluids, and medicine for fever. It is important to rule out dengue before using certain pain relievers. Prevention is the most effective way to stay safe. People can use insect repellent and mosquito nets to avoid bites.

Controlling mosquito populations is also vital. This involves removing standing water where mosquitoes lay eggs. Vaccines have been approved for use in the United States and the European Union. Once a person is immune, that protection may last a lifetime.