Discover how Crimean-Congo Hemorrhagic Fever is transmitted and learn about the different modes of transmission on Meri Sehat.

How Is Crimean-Congo Hemorrhagic Fever Transmitted?

Humza Khizer

Overview

First described in the 1940s among Russian soldiers in Crimea, the zoonotic disease has now become endemic in several countries across the world<a href="#accordion">[1]</a>. Outbreaks have been recorded in Africa, Asia, the Middle East, and Europe<a href="#accordion">[2]</a>. 
 
Recent data reveals that the incidence of Crimean Congo hemorrhagic fever (CCHF) has increased rapidly across the World Health Organization Eastern Mediterranean Region (WHO EMR)<a href="#accordion">[3]</a>. However, despite the rising incidence, there is a lack of data on the burden of the disease in the region. 
 
In Pakistan, there is a biannual surge in the cases of CCHF, with the majority appearing between March to May and August to October<a href="#accordion">[3]</a>. With <a href="https://merisehat.pk/disease/congo-virus-and-eid-ul-adha">Eid-ul-Adha</a> falling in June this year, it is expected that the country will once again face a rise in cases and deaths. 
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Understanding the Crimean-Congo Hemorrhagic Fever

Pakistan currently ranks fourth for CCHF cases in Asia, right behind Turkey, Russia, and Iran<a href="#accordion">[3]</a>. Karachi, Rawalpindi, and areas of Balochistan report the greatest number of cases<a href="#accordion">[3]</a>.

Since January of 2023, 16 cases of the CCHF virus have been reported in Balochistan, with 11 occurring within May<a href="#accordion">[4]</a>. Thus, further emphasizing the looming threat to the country&rsquo;s public health.

The tick-borne viral disease is characterized by a sudden onset of fever, headache, back pain, abdominal pain, and vomiting. This can then later progress to severe nose bleeds, large rashes, and bleeding from injection sites. The disease has a case fatality rate of 10-40%, with deaths mostly occurring in the second week of the illness<a href="#accordion">[5]</a>.

There are currently no treatments for the viral disease. Treatment is primarily supportive; however, the antiviral drug Ribavirin has shown promise in treating CCHF infection. 
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The geographical distribution of CCHF depends on that of the ixodid ticks, particularly of the Hyalomma genus. Ticks serve as the principal vector and a reservoir of the CCHF virus and typically prefer warm and dry climates.

During the spring and summer months, the larvae and nymphs feed on small animals, such as rodents and rabbits, and birds to develop into the adult form<a href="#accordion">[6]</a>. The adult ticks then feed on several large wild and domestic animals, such as cattle, goats, sheep, and camels, transmitting the infection. Thus, the animals also serve as hosts for the virus.

The virus can remain in ticks for several months or even years, transmitting the CCHF virus to other ticks, animals, and humans. 
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Although animals are asymptomatic, they can replicate the virus and serve as a source of infection for both humans and ticks. Furthermore, the migratory patterns of these animals and the trade of infected livestock play a key role in the distribution of the disease and transmission to humans.

Humans can contract the virus through the bite of an infected tick. In rural areas, where exposure to ticks is high, humans report a greater number of CCHF cases<a href="#accordion">[6]</a>. Contact with infected animal blood and tissues, for example in butchers&rsquo; shops, can also lead to infections in humans. 
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Human-to-human transmission is common in healthcare settings. Exposure to the blood, tissues, organs, or other bodily fluids of infected humans is a common mode of transmission. In healthcare settings, contaminated medical instruments play a key role in the spread of disease. Thus, healthcare workers are at a high risk of contracting infection<a href="#accordion">[6]</a>. The absence of personal protective equipment further contributes to nosocomial transmission due to splash or needlestick injuries<a href="#accordion">[6]</a>.

While sexual transmission has not been proven as a possible mode of transmission for the Crimean-Congo hemorrhagic fever virus, one study has suggested a possible link<a href="#accordion">[6]</a>. However, further research is needed. Researchers are also assessing the possibility of aerosol transmission in causing CCHF<a href="#accordion">[6]</a>. 
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The following people are at the greatest risk of contracting Crimean-Congo hemorrhagic fever:<a href="#accordion">[7]</a> 
&nbsp;

<ul>
	<li>Animal herders</li>
	<li>Livestock workers</li>
	<li>Slaughterhouse workers</li>
	<li>Butchers</li>
	<li>Veterinarians</li>
	<li>Healthcare workers 
	&nbsp;</li>
</ul>

Animal and animal skin trade within the country and between Pakistan, Afghanistan, and Iran plays a major role in the spread of the CCHF virus among people who work with animals<a href="#accordion">[3]</a>. 
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Conclusion

The changing climate, increase in the number of ticks, increasing exposure of animals and humans, and lack of surveillance systems have led to an increase in CCHF cases and deaths, in endemic and new regions. Thus, there is a need for effective vector control strategies, awareness programs, and the implementation of regulatory checks for animals. Healthcare workers should be provided with adequate protective gear when dealing with patients infected with CCHF.

 
Furthermore, added measures should be taken during Eid-ul-Adha to reduce the risk of transmission to the public. This includes quarantine measures while importing animals, regular use of pesticides, proper butchering practices, adequate disposal of animal carcasses and blood, and the creation of isolation wards in hospitals. 
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Key Points

<ul>
	<li>Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral disease characterized by fever and hemorrhage.</li>
	<li>The disease has a case fatality rate of 10-40%.</li>
	<li>In Pakistan, there is a biannual surge in the cases of CCHF, with the majority appearing between March to May and August to October.&nbsp;</li>
	<li>The geographical distribution of CCHF depends on that of the ixodid ticks, particularly of the Hyalomma genus.</li>
	<li>Ticks serve as the principal vector and a reservoir of the CCHF virus and typically prefer warm and dry climates.</li>
	<li>Although animals are asymptomatic, they can replicate the virus and serve as a source of infection for both humans and ticks.</li>
	<li>The virus can remain in ticks for several months or even years, transmitting the CCHF virus to other ticks, animals, and humans.</li>
	<li>Humans can contract the virus through the bite of an infected tick or contact with infected animal blood and tissues.</li>
	<li>Animal and animal skin trade within the country and between Pakistan, Afghanistan, and Iran plays a major role in the spread of the CCHF virus among people who work with animals.</li>
	<li>Shepherds, veterinarians, butchers, and healthcare workers are most at-risk of contracting the disease.</li>
	<li>The changing climate, increase in the number of ticks, increasing exposure of animals and humans, and lack of surveillance systems have led to an increase in CCHF cases and deaths, in endemic and new regions. 
	&nbsp;</li>
</ul>

[1]  Bernard C, Holzmuller P, Bah MT, et al. Systematic review on Crimean–Congo hemorrhagic fever enzootic cycle and factors favoring virus transmission: Special focus on France, an free-disease area in Europe. Frontiers in Veterinary Science. 2022;9. doi:10.3389/fvets.2022.932304.

[2] Crimean–Congo Hemorrhagic Fever: Treatment and future perspectives. Medscape.

[3] Al-Abri SS, Abaidani IA, Fazlalipour M, et al. Current status of Crimean-Congo hemorrhagic fever in the World Health Organization Eastern Mediterranean Region: issues, challenges, and future directions. Int J Infect Dis. 2017;58:82-89. doi:10.1016/j.ijid.2017.02.018.

[4] Hussain A. Two Congo virus-related deaths cause alarm in Pakistan. Health News | Al Jazeera.

[5] Crimean-Congo hemorrhagic fever. World Health Organization.

[7] Risk of exposure. Centers for Disease Control and Prevention.

[6] Aslam S, Latif MS, Daud M, et al. Crimean-Congo hemorrhagic fever: Risk factors and control measures for the infection abatement. Biomed Rep. 2016;4(1):15-20. doi:10.3892/br.2015.545.

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