What should you know about Congo virus?

The deadly virus causes severe viral haemorrhagic fever outbreaks with a case fatality rate of 10–40%. It is found in a wide range of wild and domestic animals such as cattle, sheep and goats.

Animals become infected by the bite of infected ticks and the virus remains in their bloodstream for about one week after infection, allowing the tick-animal-tick cycle to continue when another tick bites.

Transmission

The virus is transmitted to people either by tick bites or through contact with infected animal blood or tissues during and immediately after slaughter. The majority of cases have occurred in people involved in the livestock industry, such as agricultural workers, slaughterhouse workers and veterinarians.

Human-to-human transmission can occur resulting from close contact with the blood, secretions, organs or other bodily fluids of infected persons. Hospital-acquired infections can also occur due to improper sterilization of medical equipment, reuse of needles and contamination of medical supplies.

 Signs and symptoms

The length of the incubation period depends on the mode of acquisition of the virus ranging from three to a maximum of nine days.

The onset of symptoms is sudden, with fever, muscle ache, dizziness, neck pain and stiffness, backache, headache, sore eyes and sensitivity to light. There may be nausea, vomiting, diarrhoea, abdominal pain and sore throat, followed by sharp mood swings and confusion. After two to four days, the agitation may be replaced by sleepiness and depression.

There is usually evidence of hepatitis, and severely ill patients may experience rapid kidney deterioration, sudden liver failure after the fifth day of illness. The mortality rate from CCHF is approximately 30% with death occurring in the second week of illness.

 Prevention and control

 Controlling CCHF in animals and ticks

It is difficult to prevent or control CCHF infection in animals and ticks as the infection in domestic animals is usually not apparent. There are no vaccines available for use in animals.

Reducing the risk of infection in people

There is currently no safe and effective vaccine widely available for human use. The only way to reduce infection in people is by raising awareness of the risk factors and educate people about the measures they can take to reduce exposure to the virus.

Public health advice should focus on several aspects.

 Reducing the risk of tick-to-human transmission:

• Wear protective clothing (long sleeves, long trousers)
• Wear light coloured clothing to allow easy detection of ticks on the clothes
• Use approved acaricides (chemicals intended to kill ticks) on clothing
• Use approved repellent on the skin and clothing
• Regularly examine clothing and skin for ticks; if found, remove them safely
• Seek to eliminate or control tick infestations on animals or in stables and barns
• Avoid areas where ticks are abundant and seasons when they are most active

Reducing the risk of animal-to-human transmission

• Wear gloves and other protective clothing while handling animals or their tissues in endemic areas, notably during slaughtering, butchering and culling procedures in slaughterhouses or at home
• Quarantine animals before they enter slaughterhouses or routinely treat animals with pesticides two weeks prior to slaughter

Reducing the risk of human-to-human transmission in the community

• Avoid close physical contact with CCHF-infected people
• Wear gloves and protective equipment when taking care of ill people
• Wash hands regularly after caring for or visiting ill people

Health-care workers caring for patients with suspected or confirmed CCHF should implement standard infection control precautions. These include basic hand hygiene, use of personal protective equipment, safe injection practices and safe burial practices.