Chikungunya

Chikungunya: description

Chikungunya is a feverish infectious disease. It is triggered by the Chikungunya virus. This pathogen, also known as CHIK virus, is transmitted to humans by mosquitoes. The name comes from Tanzania. In the language of the Makonde Chikungunya means, for example, “warping” or “becoming bent”, indicating the typical Chikungunya symptoms, namely joint and muscle pain.

Chikungunya occurs in many Asian and African countries, including the tropical regions of the Indian subcontinent and the Pacific Islands. In 2013, Chikungunya met Caribbean islands and spread for the first time in the region of North, Central and South America. Previously, there were only isolated cases of returnees occurred.

In Europe so far only transfers from Italy (2007 scarcely 200 sick ones by a from south India returned tourists) and France were proven. Chikungunya is one of the “travel diseases” due to its spread.

In 2014, the Chikungunya fever was observed in 162 vacationers, according to the Robert Koch Institute. The year before, it was only 16. As a reason for the increase, the spread of Chikungunya virus in the American countries is suspected. The number of Asian tiger mosquitoes – as a typical transmitter of the CHIK virus – is also increasing in Germany. But it has not yet come to disease transmissions.

Chikungunya: symptoms

The first symptoms of Chikungunya disease appear after about two to seven, sometimes only after twelve days (incubation period). Infected people suddenly get high fever (39 degrees Celsius average) and headaches. In some cases, the increased body temperature drops abruptly after a few days, but then increases rapidly (about one to three days, sometimes only a week later). Physicians speak in this case of a biphasic fever course. Due to the rapid rise in temperature, infants and toddlers may experience febrile convulsions.

Typical Chikungunya symptoms are also severe joint and muscle pain (arthralgia and myalgia) that occur from the beginning. These are sometimes so unbearable that those affected can hardly stand. In some cases, patients also complain of swollen joints and lymph nodes. Conjunctivitis, cervical and abdominal pain are among the rare but possible Chikungunya symptoms. The heavily perfused, hot skin (flush) can sometimes be followed by an itchy, gnarled patchy rash (maculopapular rash). Chikungunya’s severe malady, accompanied by fatigue and nausea, dies down after about one to two weeks.

The Chikungunya symptoms are sometimes very strong. However, not every infected person develops signs of the disease. In some cases, Chikungunya is also symptomless. In about one quarter of those affected, there are more severe illnesses with punctate skin bleeding (petechiae) and mucosal bleeding (eg nosebleeds). In this case, doctors speak of a hemorrhagic Chikungunya fever, which is why Chikungunya is also counted among the haemorrhagic fever diseases.

Chikungunya: causes and risk factors

Two points play a crucial role in the causes of Chikungunya disease. First, the Chikungunya virus itself as a pathogen, on the other hand, its transmission to humans.

Chikungunya virus

The CHIK virus belongs to the family of the so-called Togaviridae and the large genus of alphaviruses. Chikungunya is an RNA virus and was first described in 1952/53 during an outbreak in Tanzania. It’s similar to the O’nyong-nyong virus. Other typical togaviruses are, for example, the Ross River virus, the Eastern and Western Encephalitis virus or the rubella virus. The viruses spread through the lymph nodes and blood. How exactly the virus attacks the human cells is still under investigation. Ingested there, the pathogen uses the cellular components to multiply. The Chikungunya virus is divided into three variants due to the smallest structural differences, one West African, one East Central South African and one Asian. It should therefore be able to adapt to new geographical circumstances.

Transmission of the Chikungunya virus

The CHIK virus is transmitted almost exclusively by mosquitoes from person to person. Classic representatives are mosquitoes of the genus Aedes aegypti, Aedes albopictus, Aedes africanus, Aedes furcifer and Mansoniaspezies. But also mosquitoes of the Culex genus are possible transmitters. The virus spreads and multiplies after the sting in the human body. With renewed stitches the mosquito picks up the Chikungunya virus again and transfers it to other persons.

This cycle has also been observed in meerkats, baboons and rodents (jungle cycle). However, the animals are only intermediate carriers of the virus, which is also transmitted by mosquito bites ultimately from the animals to humans (bridge transfer). Special attention should be paid to the mosquito species Aedes albopictus. Known as the Asian tiger mosquito, it is currently spreading around the world and is responsible, among other things, for the transmissions in Italy. Also in Germany in 2007 their eggs, in 2011 finally living specimens were discovered.

This small (5mm), black-silver-white striped mosquito is very active. In addition, it transmits not only the Chikungunya, but also the West Nile, Yellow Fever and Dengue virus. Chikungunya was therefore observed simultaneously with dengue fever, especially in India and Southeast Asia. Other mosquito species can cause several diseases – for example, Aedes aegypti yellow fever.

risk groups

People with high blood pressure, blood sugar disease or heart failure, those over the age of 65, and newborns are at an increased risk of the Chikungunya virus causing a serious illness. Pregnancy is an equally dangerous risk factor because mothers can transmit the virus to their child.

Chikungunya: diagnosis and examination

If you suspect that you have Chikungunya, you should consult your family doctor or a specialist in tropical medicine. Since clear early symptoms are missing, the collection of medical history (anamnesis) is of crucial importance. The doctor first asks for typical symptoms (and their course). In particular, information on recent trips is important. You may be asked the following questions:

• Since when do the complaints exist?
• When was the last time you were abroad?
• Where did you go? How long was your stay in the travel destination?
• Were you stung by mosquitoes?
• Do you have fever? Or have you recently measured elevated body temperature?
• Have your symptoms abated in the meantime and are now increasing again (as an indication of the possible biphasic Chikungunya course)?
• Do you have (unbearable) joint pain or swelling?

After the medical history, your doctor will examine you physically. Among other things, he can measure your body temperature and scan your lymph nodes. He will pay particular attention to the joints and assess any possible swelling or reddening of the skin.

laboratory tests

There are several laboratory procedures to ensure the diagnosis Chikungunya. For this, the doctor takes several blood samples. Nonspecific blood levels may be altered and generally indicate a physical condition. These include, for example, a reduction in white (lymphopenia) and red blood cells (anemia) and platelets (thrombocytopenia). In severe cases, for example, liver enzymes may also be elevated.

For reliable detection, the Chikungunya virus can either be isolated directly or its genetic material can be detected. In addition, one tests infected blood for specific antibodies against Chikungunya. The virus itself can be bred within the first three days in certain cultures. Specific proteins of the human immune system, so-called immunoglobulin (Ig) M antibodies, usually appear five to seven days after onset of disease and remain detectable for up to six months. IgG antibodies can be determined approximately from the second week and months later. Through the so-called polymerase chain reaction (PCR) parts of the virus genome (viral RNA) can be duplicated and confirm the Chikungunya fever.

Dengue fever and other diseases

In the investigation on Chikungunya, the doctor will exclude other diseases, especially other tropical diseases. These include leptospirosis, malaria, diseases caused by other alphaviruses (for example, O’nyong-nyong, Ross river), rubella, enterovirus and parvovirus infections, as well as rheumatic diseases such as post-infectious arthritis. Due to similar symptoms, but a more severe disease, dengue fever should be considered. The following table compares chikungunya with dengue fever:

In addition, the laboratory values ​​usually differ. While the white blood cells are usually reduced in Chikungunya, their number rarely changes in dengue. The reverse is true for the platelets. They are especially humiliated with dengue fever. If you have symptoms such as fever, headache, body aches, nausea and vomiting during or after a trip, especially in high-risk areas, you should consult a doctor immediately.

Chikungunya: treatment

There is no treatment that directly combats and eliminates the Chikungunya virus. Therefore, only the symptoms of the disease can be treated and alleviated. It is crucial bed rest and adequate hydration, as the body loses much water, especially during fever. Painkillers (analgesics) and fever (antipyretics) soften typical Chikungunya symptoms. For this purpose, especially non-steroidal anti-inflammatory drugs (anti-inflammatory drugs, NSAIDs) are suitable.

In case of persistent joint pain, painkillers (locally applied) corticosteroids and physiotherapy can be beneficial. In Dengue fever risk areas, acetaminophen (acetaminophen) is usually used to reduce the risk of bleeding. Acetylsalicylic acid (ASA), which disturbs the function of platelets, should therefore be avoided. In severe chikungunya fever course, intensive care monitoring may be necessary. Also with other illness symptoms such as conjunctivitis the treatment is extended accordingly.

Chikungunya vaccination

A vaccine containing inactivated chikungunya virus particles is currently being tested. However, a medical provision is not yet possible.

Chikungunya: disease course and prognosis

The Chikungunya virus can be different. In some cases, it does not trigger any symptoms. If it comes to Chikungunya fever, this usually heals without consequences within a few weeks. However, the joint complaints can sometimes last for months and occur at different joints. Especially in infants, the virus can also affect the liver or the nervous system. Although these severe disease courses are very rare, they represent a life-threatening situation. On average, about 4 out of 100 people die from chikungunya. In infants, the risk of dying from Chikungunya is slightly higher.

Prevent Chikungunya

The Chikungunya virus can neither be treated nor vaccinated against. Therefore, some measures should be followed to protect against mosquito bites that carry the virus. You should also avoid mosquitoes in the case of illness in the first week, because with renewed stitches, the virus is resumed and transmitted to your fellow human beings.

Use insect repellent!

Particularly effective are these so-called repellents with the active ingredients DEET, picaridine, IR3535 or plant-based lemon eucalyptus oil or products based on it, namely PMD / citriodiol.

Wear long pants and long-sleeved clothes!

For additional protection you can spray your clothes with permethrin.

Pay attention to mosquito nets, especially over the bed and on the windows!

This is especially true during sleep during the day, as the Chikungunya mosquitoes sting particularly aggressive at this time.

Avoid and eliminate water points in your environment!

Here mosquitoes multiply, which transmit Chikungunya. You should therefore empty buckets and buckets regularly or cover places where new mosquitoes can ripen. Avoid living in close proximity to ponds or similar waterholes. It may be necessary to use insecticides.

Do not travel to risk areas if you have limited health or are pregnant!

For more information about high risk areas, visit the World Health Organization, the Foreign Office website and the European or American health authorities (ECDC, CDC).

In general, you should consult a doctor immediately for general symptoms of illness (fever, nausea, vomiting, headache and body aches), especially during or after traveling to risky areas. Do not hesitate, if necessary (- experienced by the regionally frequent occurrence Chikungunya -) to visit clinics of your travel destination. In this way, a severe disease can be prevented in good time and a spread of Chikungunya be contained.