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Thursday, 22 August 2019

Congo Crimean Hemorrhagic Fever - Urdu Books World


Key facts
  • The Congo-Crimean hemorrhagic fever virus (CCHF) virus causes a series of outbreaks of viral hemorrhagic fever.
  • The mortality rate during outbreaks of CCHF reaches 40%.
  • The virus is transmitted to humans, mainly from ticks and livestock. Transmission from person to person can occur as a result of close contact with the blood, secretions, organs, or other body fluids of infected people.
  • CCHF is endemic in Africa, the Balkans, the Middle East and Asia, in countries south of the 50th parallel of north latitude.
  • There is no vaccine for humans or animals.

Congo-Crimean hemorrhagic fever (CCHF) is a widespread disease caused by the tick-borne virus (Nairovirus) of the Bunyaviridae family. CCHF virus causes outbreaks of severe viral hemorrhagic fever with a mortality rate of 10-40%.

CCHF is endemic in Africa, the Balkans, the Middle East and Asian countries south of the 50th parallel of northern latitude - the geographical border of the distribution of ticks, which is the main carrier.

Congo-Crimean hemorrhagic fever virus in animals and ticks.
CCHF virus carriers include a wide range of wild and domestic animals such as cattle, sheep and goats. Many birds are resistant to this infection, but ostriches are susceptible to it, and among them there may be high rates of infection in endemic areas where they are the source of infection in cases of human disease. For example, one of the past outbreaks of the disease occurred at an ostrich slaughter in South Africa. There are no obvious signs of disease in these animals.

Animals become infected by being bitten by infected ticks, and the virus remains in their bloodstream for approximately one week after infection, which, with subsequent tick bites, ensures the continuation of the tick-animal-tick cycle. Although several types of ticks can become infected with the CCHF virus, the main carriers are ticks of the Hyalomma species.

Transmission of infection
CCHF virus is transmitted to humans either by tick bites or by contact with infected blood or animal tissues during and immediately after slaughter. Most cases of infection occur in people employed in livestock farming, such as farm workers, slaughterhouse workers and veterinarians.

Transmission from person to person can occur as a result of close contact with the blood, secretions, organs, or other body fluids of infected people. Cases of nosocomial infection may also occur as a result of inadequate sterilization of medical equipment, reuse of needles and contamination of medical supplies.

Signs and Symptoms
The duration of the incubation period depends on the method of infection with the virus. After infection by a tick bite, the incubation period usually lasts one to three days, with a maximum duration of nine days. The incubation period after contact with infected blood or tissues usually lasts five to six days with a documented maximum period of 13 days.

Symptoms appear suddenly with fever, myalgia (muscle pain), dizziness, pain and stiffness of the neck, back or lower back pain, headache, inflammation of the eyes and photophobia (sensitivity to light). Nausea, vomiting, diarrhea, pain in the abdomen and sore throat can be observed, followed by sudden mood swings and confusion. After two to four days, excitement can be replaced by drowsiness, depression and fatigue, and pain in the abdomen can be localized in the upper right part with detectable hepatomegaly (enlarged liver).

Other clinical signs include tachycardia (palpitations), lymphadenopathy (swollen lymph nodes), and a petechial rash (a rash caused by bleeding into the skin) on the inside of the mucous membranes, such as in the mouth and throat, as well as on the skin. The petechial rash can go into a larger rash called ecchymosis, and other hemorrhagic events. Symptoms of hepatitis are usually observed, and after the fifth day of illness in seriously ill patients, there may be a rapid deterioration in kidney function and sudden liver or pulmonary failure.

The mortality rate from CCHF is approximately 30%, with death occurring in the second week of the disease. In recovering patients, improvement usually begins on the ninth or tenth day after the onset of the disease.

Diagnostics

CCHF virus infection can be diagnosed with several different laboratory tests:
 
  • Enzyme immunoassay (ELISA);
  • Detection of antigens;
  • Serum neutralization;
  • Reverse transcriptase polymerase chain reaction (RT-PCR);
  • Virus isolation in cell cultures.

In terminally ill patients, as well as patients in the first few days of the disease, measurable antibody formation usually does not occur, therefore, diagnosis in such patients is carried out by detecting the virus or RNA in blood or tissue samples.

Testing patient samples presents an extremely high biological risk and should only be carried out under conditions of maximum biosafety. However, if samples are inactivated (e.g., by viricides, gamma radiation, formaldehyde, exposure to high temperatures, etc.), they can be handled under basic biosafety conditions.

Treatment
The main approach to managing CCHF in humans is conventional supportive care with symptom management.

The antiviral drug ribavirin leads to obvious positive results in the treatment of CCHF infection. Both oral and intravenous dosage forms are effective.

Disease Prevention and Control
Fight against CCHF among animals and ticks

Robert Swanepoel / NICD South Africa
It is difficult to prevent and control CCHF infection among animals and ticks, because the tick-animal-tick cycle usually goes unnoticed and the infection in domestic animals usually proceeds without obvious signs. In addition, tick-borne ticks are numerous and widespread, so the only practical option for properly managed livestock enterprises is to control ticks with acaricides (chemicals used to kill ticks). For example, after an outbreak of the disease in an ostrich slaughter in South Africa (mentioned above), measures were taken to ensure that ostriches remained in the quarantine free from ticks for 14 days before slaughter. This measure helped to reduce the risk that the animal was infected during slaughter and prevent the infection of people in contact with animals.
 There are no vaccines for use in animals.

Reducing the risk of human infection
Although an inactivated vaccine derived from mouse brain tissue has been developed against CCHF that has been used on a small scale in Eastern Europe, there is currently no safe and effective vaccine for widespread use in humans.

In the absence of a vaccine, the only way to reduce the number of infections among people is to raise awareness of risk factors and educate people about the measures they can take to limit exposure to the virus.

Public health recommendations should focus on several aspects.

  • Reducing the risk of transmission of the virus from ticks to humans:

  1.  Wear protective clothing (long sleeves, long trousers);
  2.  Wear light-colored clothing that makes it easy to spot ticks on clothing;
  3.  Apply approved acaricides (chemicals used to kill ticks) for clothing;
  4.  Apply approved repellents to skin and clothing;
  5.  Regularly inspect clothing and skin for ticks; if they are detected, remove them using safe methods;
  6. To strive to prevent the defeat of animals by ticks or to fight against ticks in rooms for keeping animals;
  7.  Avoid staying in areas where there are a large number of ticks, and in those seasons when they are most active.

  • Reducing the risk of transmission of the virus from animals to humans:

  1. Keep animals in quarantine before they enter the slaughterhouse or treat the animals with pesticides in the usual manner two weeks before slaughter.

  • Reducing the risk of transmission from person to person in selected communities:

  1. Avoid close physical contact with people infected with CCHF;
  2. Wear gloves and protective clothing when caring for sick people;
  3. Wash your hands regularly after caring for or visiting sick people.


Infection control in medical facilities
Health care providers who care for patients with suspected or confirmed CCHF, or who work with samples taken from them, must follow standard infection control measures. These include basic hand hygiene, personal protective equipment, safe injection practices and safe burial practices.

As a precautionary measure, healthcare providers who care for patients directly outside the CCHF outbreak area should also follow standard infection control measures.

Samples taken from people with a proposed CCHF should be handled by specially trained staff working in properly equipped laboratories.

Recommendations for infection control in the process of assisting patients with suspected or confirmed Congo-Crimean hemorrhagic fever should be consistent with the WHO recommendations developed for Ebola and Marburg hemorrhagic fevers.

WHO activities
WHO works with partners to support CCHF surveillance, diagnostic capacity and outbreak response in Europe, the Middle East, Asia and Africa.

WHO also provides documentation to facilitate research and control of the disease and has developed a memo on standard precautions in medical settings that is designed to reduce the risk of transmission of bloodborne pathogens and other pathogens.

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