Explained: What Is Crimean-Congo Haemorrhagic Fever? All About The Tick-Borne Viral Disease Reported In Spain

Spain confirmed a case of Crimean-Congo haemorrhagic fever on July 21. Crimean-Congo haemorrhagic fever is caused by infection with Nairovirus, a tick-borne virus belonging to the Bunyaviridae family.

Hard-bodied Ixodid ticks are both a reservoir and a vector for the Crimean-Congo haemorrhagic fever virus. A person suffering from Crimean-Congo haemorrhagic fever can show symptoms such as fever, dizziness, myalgia, backache, neck pain, stiffness, sore eyes, and headache.

Source : WHO

Spain confirmed a case of Crimean-Congo haemorrhagic fever on July 21, 2022. The person infected is a middle-aged man who was admitted to a hospital in Spain's Castile and Leon region. 

According to a report by news agency Reuters, the man was admitted to a local hospital in Leon because he started showing symptoms of Crimean-Congo haemorrhagic fever after being bitten by a tick. He was later transferred to another hospital on a military plane. 

Local health authorities said in a statement that he has a tick bite and remains in a "stable condition", despite the clinical severity that this pathology implies. 

In 2011, Spain detected its first case of Crimean-Congo haemorrhagic fever. A Spanish man was bitten by a tick in 2016, following which he was diagnosed with the disease, and subsequently died.

What Is Crimean-Congo Haemorrhagic Fever?

Crimean-Congo haemorrhagic fever (CCHF) is caused by infection with Nairovirus, a tick-borne virus belonging to the Bunyaviridae family. The disease was first detected in Crimea, a peninsula in Eastern Europe, in 1944. Therefore, it was initially named Crimean haemorrhagic fever. In 1969, the disease was recognised as the cause of illness in the Congo, following which it was named Crimean-Congo haemorrhagic fever.

The Crimean-Congo haemorrhagic fever virus has a case fatality rate of 10 to 40 per cent, and results in severe viral haemorrhagic fever outbreaks. 

The disease is endemic in the Middle East, the Balkans, Africa, and some countries in Asia. It is also found in Eastern Europe, northwestern China, southern Europe, and the Indian subcontinent.

Different wild animals and domestic animals such as sheep, goats, and cattle may serve as the hosts of the Crimean-Congo haemorrhagic fever virus. While several birds are resistant to infection with the virus, ostriches are susceptible. In endemic areas, ostriches may show a high prevalence of infection, and spread the disease to humans. Earlier, an outbreak of Crimean-Congo haemorrhagic fever had occurred at an ostrich abattoir in South Africa. 

When ticks infected with the Crimean-Congo haemorrhagic fever virus bite livestock animals, the latter get infected as well. After this, the virus remains in their bloodstream for about one week. This allows the tick-animal-tick cycle to continue when another tick bites, according to the World Health Organization (WHO). The principal vector for the virus belongs to the genus Hyalomma, which includes hard-bodied ticks common in Asia, Europe, and North Africa. 

How Is The Crimean-Congo Haemorrhagic Fever Virus Transmitted?

The Crimean-Congo haemorrhagic fever virus is spread either by tick bites or through contact with infected animal blood or tissues during or immediately after slaughter, according to the WHO. Ticks which are both a reservoir and a vector for the Crimean-Congo haemorrhagic fever virus are called Ixodid ticks. 

Agricultural workers, veterinarians, and slaughterhouse workers are susceptible to infection. 

Close contact with blood, organs, secretions, and bodily fluids of infected persons can result in human-to-human transmission of the disease. 

The virus can spread from an infected human to another through contact with infectious blood or body fluids. Hospitals in which people infected with Crimean-Congo haemorrhagic fever are treated, and where medical equipment are not properly sterilised, and injection needles are reused, can serve as hotspots for the virus.

What Are The Signs And Symptoms Of Crimean-Congo Haemorrhagic Fever?

The mode of acquisition of the virus determines the length of the incubation period. It may take three to nine days for the symptoms to appear following infection by a tick bite. When a person is infected through contact with infected blood or tissues, the incubation period is usually five to six days, with a maximum of 13 days.

A person suffering from Crimean-Congo haemorrhagic fever can show symptoms such as fever, dizziness, myalgia, backache, neck pain, stiffness, sore eyes, headache, joint pain, and photophobia, which refers to sensitivity to light. Other symptoms include abdominal pain, vomiting, nausea, diarrhoea, sore throat, confusion, and sharp mood swings. The agitation may be replaced by sleepiness and depression, about two to four days after the onset of symptoms. Abdominal pain in Crimean-Congo haemorrhagic fever patients usually occurs in the upper right quadrant. Hepatomegaly or liver enlargement may also occur. 

According to the Centers for Disease Control and Prevention (CDC), a person suffering from Crimean-Congo haemorrhagic fever may have red eyes, a red throat, a flushed face, and petechiae or red spots on the palate. The person may also suffer from jaundice as a result of the viral disease. 

Large areas of severe bruising, uncontrolled bleeding at injection sites, and severe nosebleeds can be seen as the illness progresses. These symptoms may begin on about the fourth day of illness, and last for about two weeks. Fatality rates in patients hospitalised due to Crimean-Congo haemorrhagic fever have ranged from nine per cent to as high as 50 per cent. 

Tachycardia, or a fast heart rate, petechial rash, which is a rash caused by bleeding to the skin, and lymphadenopathy, which refers to enlarged lymph nodes, are other clinical signs for the disease. The petechial rashes may occur on internal mucosal surfaces such as the throat, in the mouth, and on the skin. As the infection progresses, the petechiae may grow into larger rashes called ecchymoses, followed by other haemorrhagic phenomena. 

Rapid kidney deterioration, pulmonary failure, or sudden liver failure may occur in severely ill patients after the fifth day of illness.

According to the WHO, the mortality rate from Crimean-Congo haemorrhagic fever is about 30 per cent, and death occurs in the second week of illness. For the patients who recover, improvement starts on the ninth or tenth day after the onset of illness. Recovery from the disease is slow. 

How Can Crimean-Congo Haemorrhagic Fever Be Diagnosed?

Crimean-Congo haemorrhagic fever can be diagnosed with the help of several laboratory tests such as serum neutralisation, antigen detection, and reverse transcriptase polymerase chain reaction (RT-PCR) assay, among others. Immunoglobulin G and Immunoglobulin M antibodies against the virus can be detected using a technique known as enzyme-linked immunosorbent assay (ELISA). 

The combination of detection of the viral antigen using ELISA antigen capture, detection of viral RNA sequence in the blood using RT-PCR, and virus isolation can be used to diagnose a patient with a clinical history compatible with Crimean-Congo haemorrhagic fever. 

In patients who survive, antibodies can be found in the blood later in the course of the disease, but the virus, antigen, and viral DNA are neither present nor detectable at that stage.

A measurable antibody response is not seen in patients in the first few days of the illness, or in patients with fatal disease. Therefore, they should be diagnosed by detection of the virus or RNA in tissue or blood samples.

Patients suspected to have the disease should be tested under maximum biological containment conditions because patient samples pose an extreme biohazard risk. The samples can be manipulated in a basic biosafety environment if they have been inactivated using heat, formaldehyde, or gamma rays.

How Can Crimean-Congo Haemorrhagic Fever Be Treated?

The main approach to managing Crimean-Congo haemorrhagic fever in people is general supportive care. Patients diagnosed with Crimean-Congo haemorrhagic fever should maintain fluid balance and electrolyte levels in their bodies. They should also pay attention to oxygenation, and to appropriate treatment of secondary infections.

People infected with the disease can be treated using the antiviral drug ribavirin, which can be administered orally as well as intravenously.

How To Prevent Crimean-Congo Haemorrhagic Fever?

Crimean-Congo haemorrhagic fever outbreaks can be prevented by controlling the disease-causing virus in animals and ticks, controlling infection in health-care settings, and reducing the risk of infection in people. 

Acaricides, which are chemicals intended to kill ticks, can be used to manage livestock production facilities to prevent spread of the virus causing Crimean-Congo haemorrhagic fever among livestock animals. No vaccines are available for use in animals. 

The risk for tick-to-human transmission can be reduced by wearing light-coloured clothing to allow easy detection of ticks on the clothes, wear protective clothing, use approved repellent in the skin, eliminate tick infestations on animals, use approved acaricides on clothing, and regularly examine clothing and skin for ticks.

The risk of animal-to-human transmission of Crimean-Congo haemorrhagic fever can be reduced by wearing gloves and other protective clothing while handling animals. 

In order to reduce the risk of human-to-human transmission of the disease, people should avoid close physical contact with those infected with Crimean-Congo haemorrhagic fever, wash hands regularly after caring for ill people, and wear protective equipment when taking care of infected people.

People should be educated about the measures that need to be taken to reduce exposure to the Crimean-Congo haemorrhagic fever. It is important to raise awareness about the risk factors for the disease. 

In order to control infection in health-care settings, standard infection control precautions should be implemented. The precautions include use of personal protective equipment, basic hand hygiene, safe burial practices, and safe injection practices. 

In order to control infection while providing care to patients with suspected or confirmed Crimean-Congo haemorrhagic fever, healthcare workers should follow the recommendations developed by the WHO for Ebola and Marburg haemorrhagic fever. 

The CDC recommends the use of insect repellents containing DEET (N, N-diethyl-m-toluamide) to ward off ticks. Agricultural workers and people working with animals should wear gloves and other protective clothing to avoid contact with the blood and body fluids of livestock or humans showing symptoms of infection. 

An inactivated, mouse brain-derived vaccine against Crimean-Congo haemorrhagic fever has been developed and used on a small scale in Eastern Europe, according to the CDC. However, no safe and effective vaccine is currently available for human use, and further research must be conducted to develop potential vaccines and determine the efficacy of treatment options including ribavirin and other antiviral drugs. 

Who Are At The Risk Of Exposure To The Crimean-Congo Haemorrhagic Fever Virus?

People who are at risk of Crimean-Congo haemorrhagic fever include animal herders and livestock workers living in endemic areas. 

Healthcare workers in endemic areas, and international travellers with contact with livestock in those regions are also at risk of infection.