Crimean-Congo haemorrhagic fever

The first case of this tick-borne viral fever was reported in Crimea in Eastern Europe, in 1944. The same viral fever was also widely reported in Congo, on the African continent, in 1969. Hence, the name Crimean-Congo Hemorrhagic Fever.

Congo fever is endemic to several parts of the world where these ticks live - the list includes the former Soviet Union nations, the Mediterranean region, north-west China, Central Asia, Africa, the Middle-East and India.

Healthcare workers and people working in the livestock industry are at higher risk of getting Congo fever.

A person infected with the Congo fever virus manifests a range of signs and symptoms after the incubation period - if a person gets the infection after being bitten by a tick, the incubation period is shorter - usually one to three days. If a person gets Nairovirus infection through contaminated blood and body fluids, the incubation period becomes slightly longer - usually five to six days, but symptoms can take up to 13 days to show.

The most commonly reported symptoms of Congo fever are:

• Sudden fever
• Myalgia (muscle pain)
• Dizziness (lightheadedness)
• Pain and stiffness in the neck
• Headache
• Backache
• Soreness of eye
• Photophobia (sensitivity to light)
• Nausea and vomiting
• Diarrhoea
• Abdominal pain
• Sore throat
• Mood swings
• Confusion
• Lymphadenopathy (enlargement of lymph nodes)
• Tachycardia (increased heart rate)
• Petechial rash (redness on the skin, oral cavity and throat due to the presence of tiny bleeding points)
• In severe cases, the tiny bleeding point under the skin becomes large, giving rise to bigger rash known as ecchymosis
• Hemorrhage can occur in the internal organs of the body if the disease is not treated promptly
• In severe cases, patients can develop hepatitis, sudden liver failure, kidney failure or respiratory failure after the fifth day of onset of symptoms

Ixodid or hard ticks act as a reservoir for the Congo fever virus - Niarovirus. Animals that have been bitten by infected ticks, including domesticated animals like goat, sheep, camels and hare, act as amplifying hosts - they help in the spread of the disease among humans.

When an animal is bitten by an infected tick, the virus enters their bloodstream and causes infection. Unfortunately, signs of the disease remain hidden in animals.

Transmission of the disease occurs in several ways:

• If the infected tick bites a human being
• If an infected animal is bitten by a non-vector tick - causing tick-animal-tick cycle, now, this newly infected tick will carry the infection for their lifetime
• If a human comes in contact with the blood of an infected animal, say, while slaughtering the animal or in a veterinary set-up where they have to handle the blood and tissues of infected animals
• If you come in contact with the blood or bodily fluid of an infected person
• Through contaminated medical equipment (hospital-acquired infections)

Congo fever can be elicited from the presence of Nairovirus or Nairovirus antibodies in the blood - our immune cells produce antibodies to fight infection caused by pathogen like viruses.

Some laboratory tests that can help in diagnosing Congo fever are:

• Enzyme-linked immunosorbent assay (ELISA)
• Antigen detection
• Serum neutralization
• Reverse transcriptase-polymerase chain reaction (RT-PCR) assay
• Virus isolation by cell culture

Healthcare professionals are at high risk for infection - it can be transmitted through direct contact with the blood and tissue of a patient. Therefore, they are strictly advised to run the tests under maximum biological containment conditions. Another way is to counter the enhanced risk to healthcare professionals who have to test samples, is by using virucides, gamma rays, formaldehyde or heat to create what is known as a "biosafety environment".

The mainstay treatment for Congo fever is supportive in nature - it is crucial to maintain fluid and electrolyte balance, adequate oxygen supply, normal heart and breathing rate, and to manage any internal bleeding to avoid complications.

Patients usually respond to the antiviral drug ribavirin. 

For now, there is no vaccine for CCHF. However, research is on to develop a vaccine for the potentially fatal disease.

People residing in endemic regions, like India, are at risk for the disease. But we can always take preventive measures to avoid getting the infection. Try these tips:

• Use insect repellant on exposed skin as well as your clothing if you go into a field or anywhere you are likely to come in contact with animals. Repellants containing DEET (N, N-diethyl-m-toluamide) are said to be most effective for killing ticks
• Wear clothes that cover your whole body. Don't forget to wear gloves if you work with animals
• If you are a medical professional or a lab technician, take adequate precautions while handling the blood samples and tissue of patients who are suspected to have Congo fever