On August 25th, the first two autochthonous cases of Crimean-Congo hemorrhagic fever (CCHF) were confirmed in Spain, resulting in the death of one man [1]. Approximately 200 people were exposed to the two infected cases, and some were quarantined while monitored for symptoms [1]. As of September 18th, the second case, an ICU nurse who treated the first patient, finally tested negative for the virus. She was finally released from the hospital three days later, where she had been in isolation for almost a month [2]. This event is concerning as it shows evidence of CCHF spreading from endemic regions into unaffected areas of Western Europe.
CCHF is a disease caused from a tick-borne virus of the genus Nairovirus, in the family Bunyaviridae, and is related to Rift Valley fever and hantaviruses [3, 4]. The disease presents with sudden fever, myalgia, vomiting, diarrhea, and may develop into severe hemorrhagic disease with development of ecchymosis or bleeding from the nasopharynx and/or gastrointestinal tract [3, 5]. According to the World Health Organization (WHO), there is a case fatality rate of up 40%, with death generally occurring during the second week of illness [3]. It may take up to a year for survivors to make a full recovery. Early reports of recovering patients in South Africa have reported disease sequelae such as hair loss, weakness, impaired memory, and hepatorenal insufficiency [5].
The disease is the most geographically widespread of all tick-borne diseases in humans, and is endemic in Africa, Asia, the Middle East, and Eastern Europe, in countries south of the 50°N [5, 6]. At the time of this article, an outbreak in Pakistan has caused the death of at least 20 people this year [4].
The primary vector of CCHF virus are tick species belonging to the Hyalomma genus, but there has been evidence of the virus being carried in a variety of other ticks [3, 5]. These ticks can attach and feed on birds during their larval and nymphal stages in life [5]. These birds can then carry the ticks from endemic areas during the migration season, where the immature ticks will fall off and molt into adults [5]. This method of vector dispersal is far reaching as African H. rufipes ticks have even been found in as far north as Norway [5]. Adult ticks can feed on livestock or a passing humans and can transmit the CCHF virus to these hosts [5]. In 2010, researchers found H. lusitanicum ticks that were positive for CCHF virus on red deer nearCáceres in Extremadura, Spain. This detection in deer is located near the border with the autonomous community of Castile and León where the man contracted CCHF this year [5, 7].
Livestock and other animal trade are other possible routes of spreading CCHF. Infected animals tend to be asymptomatic and it can be difficult to determine that the CCHF virus is present until a human gets sick [5]. In 2014, a report showed a high amount of CCHF virus-positive H. aegyptium ticks were removed from spur-thighed tortoises in southeast Turkey and northwest Syria [8]. This report shows another potential and less known pathway of CCHF virus spread through illegal animal trade. From 2012 – 2013, 18,000 tortoises were recorded passing through United Kingdom airports, and 1,000 of these tortoises were quarantined at Heathrow Airport for up to six months [8]. CCHF virus infected ticks can be carried on turtles, or other wildlife, and shipped to new regions.
Aside from tick bites, the CCHF virus can also be transmitted through contact with infected fluids or tissues [3, 5]. This route of transmission primarily happens to workers in livestock slaughterhouses. Human-to-human transmission can also take place in hospital settings when inadequate personal protection is used [5]. This is the route of exposure that resulted in the second case of CCHF, in Spain – where the ICU nurse became infected after treating the index patient. This nosocomial infection illuminates the importance of increased awareness of potential CCHF cases entering hospitals in Western Europe, and using precautions when diagnoses are not yet determined.
Climate change poses a concern for the spread and emergence of CCHF in areas outside of its endemic regions. As global temperature warms, tick populations may be able to expand their geographic range into areas where they were not in existence before [5]. Higher temperatures in the fall season may allow ticks to molt from nymphs into adults where they were previously prevented by colder temperatures [5]. This could lead to a burgeoning adult tick population, seeking human or animal hosts. However, another model of the risk of the new enzootic livestock incursions of CCHF show that climate change has opposing effects in the establishment of new areas of CCHF [5, 9]. Much has yet to be determined regarding the possible effects of climate change on vectorborne disease.
There is much evidence that points to the projected spread of CCHF from endemic areas into new ones. Western European doctors should include CCHF in their potential diagnosis list when patients develop sudden fever after exposure to tick bites. While the spread of CCHF may not be able to be contained, the emergence of CCHF into new areas is something that demands vigilance from public health officials and the public alike.
The author would like to thank Andrea Rios Gonzalez for the translation of the Spanish articles used in the research of this disease outbreak.
—
Sources
1. One Dead, One In Isolation After Two Cases Of Crimean-Congo Hemorrhagic Fever Confirmed In Madrid. 2016 September 1, 2016 September 20, 2016]; Available from: https://www.thespainreport.com/articles/883-160901142820-one-dead-one-in-isolation-after-two-cases-of-crimean-congo-hemorrhagic-fever-confirmed-in-madrid.
2. Congo fever nurse discharged from Spanish hospital. 2016 September 26, 2016]; Available from: http://medicalxpress.com/news/2016-09-congo-fever-nurse-discharged-spanish.html.
3. WHO. Crimean-Congo haemorrhagic fever. 2013 September 20, 2016]; Available from: http://www.who.int/mediacentre/factsheets/fs208/en/.
4. McNeil, D.G. Doctors on Lookout for Crimean-Congo Hemorrhagic Fever in Spain. 2016 September 20, 20166]; Available from: http://www.nytimes.com/2016/09/06/health/crimean-congo-hemorrhagic-fever-spain.html?smid=tw-nythealth&smtyp=cur&_r=1.
5. Bente, D.A., et al., Crimean-Congo hemorrhagic fever: History, epidemiology, pathogenesis, clinical syndrome and genetic diversity. Antiviral Research, 2013. 100(1): p. 159-189.
6. Al-Abri, S.S. and E. Petersen, Crimean-Congo hemorrhagic fever – A ticking bomb? Travel Medicine and Infectious Disease, 2016. 14(2): p. 71-72.
7. Estrada-Peña, A., et al., Crimean-congo hemorrhagic fever virus in ticks, Southwestern Europe, 2010. Emerging Infectious Diseases, 2012. 18(1): p. 179-180.
8. Phipps, L.P., et al., Potential pathway for Crimean Congo haemorrhagic fever virus to enter the UK. Veterinary Record, 2014. 175(4): p. 100-101.
9. Gale, P., et al., Impact of climate change on risk of incursion of Crimean-Congo haemorrhagic fever virus in livestock in Europe through migratory birds. Journal of Applied Microbiology, 2012. 112(2): p. 246-257.
