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_|WHO, EURO: Epidemiology of Crimean?Congo haemorrhagic fever virus: Turkey, Russian Federation, Bulgaria, Greece, Albania, Kosovo|_
Epidemiology of Crimean?Congo haemorrhagic fever virus: Turkey, Russian Federation, Bulgaria, Greece, Albania, Kosovo
11 August 2008
Crimean-Congo Hemorrhagic fever (CCHF) is a zoonosis transmitted by ticks that cause severe outbreaks in humans.
CCHF intensified activity and outbreaks constitute a threat to public health services because of its high case fatality ratio (10-40%), its potential for nosocomial transmission, and the difficulties in case management and prevention requiring a sustained multi-sectoral approach.
In the WHO European Region, CCHF is endemic in several areas of countries and territories south of the 50? parallel north.
In these areas, the peak of CCHF activity observed during late spring and summer.
Data available for 2008 indicate CCHF virus is circulating with particular intensity in Turkey, the Balkans, and southern districts of the Russian Federation.
The information summarised below was compiled thanks to the tireless support of EpiSouth - Network for Communicable Disease Control in Southern Europe and Mediterranean Countries.
It provides a focus on the epidemiology of CCHF in selected endemic countries and territories.
Additional details on CCHF in this and other WHO Regions are available on the EpiSouth web site.
1. Background
CCHF virus is a Nairovirus of the Bunyavirus family identified in 1956 in the Congo and in 1967 in what is now Uzbekistan.
CCHF virus is enzootic in the southern part of Europe (Balkans), Turkey, the southern Russian Federation, and in several countries in the Middle East, of sub-Saharan Africa, central Asia and the western part of China.
Reservoir:
Several species of ixodid ticks (mainly Hyalomma and Amblyomma) which are endemic to the semi-desert zones of a yet greater number of countries can transmit CCHF by bite.
Animals such as wild rodents and livestock serve as amplifiers.
Transmission:
The virus causes sporadic cases in humans, essentially linked to tick bites during farming or cattle-raising activities.
Clinical presentation:
In most cases, infection in humans causes few or no symptoms, although CCHF virus may cause a severe viral haemorrhagic fever. Person-to-person transmission to carers occurs, including in the health care setting.
Incubation:
1?7 days (on average 3?5 days).
Viraemia:
appears with clinical symptoms and lasts around 10 days.
Case-fatality rate (CFR)
The literature describes CFRs as high as 40?50%, especially in severe forms diagnosed during epidemics in resource-poor settings.
Global CFR in hospitalized patients (all grades of severity), however, is closer to 2?6% according to recent data collected in Turkey and the Russian Federation.
Data from South Africa or Turkey show that the CFR can be significantly higher in patients with biologically confirmed CCHF who present clinical and biological criteria of severity.
Non-specific supportive treatment may be effective.
WHO has approved ribavirin as a specific treatment, based on limited circumstantial data in the endemic setting and experimental evidence.
A vaccine has been developed in Bulgaria for use in humans.
Discrepancies in global CFR in hospitalized patients during epidemics may therefore be explained by differences in:
* the performance of surveillance systems in detecting less-severe cases; * the sensitivity and specificity of case definitions used and their positive predictive value during epidemics; and
* diagnostic and therapeutic management.
2. CCHF situation as of mid-2008: Turkey, Russian Federation, Bulgaria, Greece, Albania, and Kosovo(1)
2.1. Turkey
In 1974, seroepidemiological studies found evidence of anti-CCHF antibodies in 26 (2.4%) of 1100 sera tested in Turkey(2).
The first symptomatic human case of CCHF in Turkey was identified in 2002.
Between 2002 and 2007, the number of confirmed CCHF cases reported in Turkey regularly increased, especially in eastern and north-eastern rural areas (Table 1 and Fig. 1).
An epidemic is now reported each year in Turkey. It is most active from April to September.
Between 1 January and 30 June 2008, a total of 688 confirmed cases (with 41 deaths, CFR: 6.0%) have been reported in Turkey.
Cases are essentially described in adults exposed to tick bites during rural activities in north-central Anatolia.
Some sporadic cases occur in other areas of Turkey.
One case was described in Kirklareli (north-west of Istanbul) in 2007.
Since 2003, 8 cases have been documented in health care workers (HCW) (with 1 death) following accidental exposure to blood or body fluids.
In some instances (study protocols), cases were treated with ribavirin.
[Table 1. Confirmed CCHF cases and deaths in Turkey, 2002?2008 (Source: Ministry of Health) ]
[Fig. 1. Confirmed CCHF cases and deaths in Turkey, 2002?2008 (Source: Ministry of Health)]
2.2. Russian Federation
Data presented here originate from the Federal Service for Surveillance on Consumer Rights Protection and Wellbeing, Ministry of Health and Social Development of the Russian Federation (Rospotrebnadzor).
Cases are described each year in the Southern Federal District (okrug).
Cases occur mainly in 3 of the 13 zones of this District: Republic of Ingushetia, Rostov oblast and Stavropol kraj.
The number of cases reported has risen progressively since 2002 (Table 2).
A total of 839 confirmed cases (with 27 deaths) has been recorded since 2002.
The yearly CFR in confirmed cases ranges from 1.7% to 11.1% with a global CFR of 3.2% for the period 2002?2008 (based on preliminary data for 2008).
[Table 2. Confirmed CCHF cases and deaths in the Southern Federal District, Russian Federation, 2002?2008 (Source: Rospotrebnadzor) ]
[Fig. 2. Confirmed CCHF cases and deaths in the Southern Federal District, Russian Federation, 2002?2008 (Source: Rospotrebnadzor) ]
2.3. Bulgaria
Some areas of Bulgaria are endemic for CCHF. On average, 10?15 cases are reported each year.
The most significant epidemic in the country occurred in 1954?1955 with a total of 487 cases (213 in 1954 and 274 in 1955). Approximately 300 of these cases were reported in the Shumen district, in the north-east of the country.
Between 1953 and 1974, a total of 1101 CCHF cases were notified in Bulgaria (CFR 17%), of which 20 were acquired during health care.
Between 1975 and 1996, the development and distribution of a human vaccine was associated with a reduction in notified cases: 271 cases (CFR: 11.4%).
Since 1997, a total of 196 suspect or confirmed cases were notified (43 deaths, CFR: 22%) (Fig. 3).
[Fig. 3: Suspect or confirmed CCHF cases in Bulgaria, 1997?2008* (Source: National Centre of Infectious and Parasitic Diseases) ]
Between March 20 and July 10, 2008, national authorities identified 7 cases of CCHF:
* 2 confirmed cases (acquired while delivering care) and 4 probable cases in Gotse Delchev county, Blagoevgrad district, in western Bulgaria(3).
* An additional probable case was identified in Sliven district.
2.4. Greece
Several seroepidemiological studies conducted in the 1970s and 1980s found evidence for the circulation of CCHF virus in Greece.
CCHF virus strain AP92 was isolated from ticks collected from goats in 1976 in Vergina village (80 km west of Thessaloniki). This strain seems to be low or not pathogenic to humans.
The virus was found in 4 (6.1%) of 65 residents of Vergina village (where strain AP92 was isolated)4 and 1.1% of over 3000 sera from apparently healthy individuals, mainly farmers and shepherds, sampled throughout Greece (0?6.2%, depending on the region)(5). The observation of higher sero-prevalence in departments close to Vergina village (Pella, Imathia, Karditsa), combined with the absence of CCHF cases, suggests that the detected antibodies were most probably against AP92 strain, which is genetically different from all other CCHF viral strains(6).
The first symptomatic case of CCHF diagnosed in Greece was confirmed in a woman who died on 25 June 2008. She was exposed to tick bite during farming activities in rural areas near Komotini (Rhodope department in the Thrace region).
Tick control measures have been implemented and the surveillance of humans has been strengthened. Surveys on humans, domestic animals and ticks have been started. There are no other identified cases to date.
2.5. Albania
The first human case of CCHF was described in Albania in 1986.
A total of 35 suspect or confirmed cases were reported between 1986 and 1990(7).
From 2001 to 2006, a yearly average of 10 suspect and 5 confirmed cases have been reported (Table 3).
[Table 3: Suspect and confirmed cases of CCHF in Albania, 2001?2006 (Source: Public Health Institute) ]
Most cases are reported in Kuk?s district, in the north-eastern part of the country, although cases are regularly reported from other areas.
Anti-CCHF antibodies were found in 1.3% of 233 sera sampled in the general population.
2.6. Kosovo
The first human cases were described in 1954 during an epidemic with 8 cases.
[Table 4 presents data on suspect and confirmed cases of CCHF between 1995 and November 2006. ]
Available data indicate a seroprevalence of around 24% in the general population living in endemic areas (centre and south-western areas).
[Table 4. Suspected and confirmed CCHF cases in Kosovo, 1995?2006 (Source: Institute of Public Health(8)) ]
3. Comments
CCHF virus is the causative agent of the viral haemorrhagic fever with the widest geographical area of circulation in the world. Among other areas, it is present in the WHO European Region (Greece, Bulgaria, Turkey, Albania, Kosovo, southern part of the Russian Federation).
Evidence of CCHF circulation can also be found in most countries on the Black Sea coastline.
Low-intensity circulation of CCHF was established in Turkey and Greece over 30 years ago.
The virus has recently emerged on a larger scale in Turkey. This could be due to the multiplication of vectors and reservoir animals (hares, boars) in rural areas. Temperature changes may also play a role.
Data collected in Turkey and the Russian Federation show lower CFRs than those initially documented in endemic settings. This is due to the quality of diagnostic and medical management of cases, and to a sensitive system of detection through systematic screening of people referred for tick bites in endemic areas.
Some continue to debate the usefulness of ribavirin treatment in the early stages of infection.
In all countries concerned, the vast majority of cases is reported in known endemic areas. The occurrence of human CCHF cases, even in clusters, with a documented exposure to tick bites or to blood or body fluids of confirmed or suspect cases, is not an unexpected event and does not require specific measures other than those implemented by national authorities and informing tourists of available preventive measures.
Simple precautions can be observed to prevent tick bites (repellents, wearing long garments, careful removal of ticks using forceps in case of bite)(9).
No case has been reported in a tourist visiting any of the countries discussed here.
To date, a single case of imported CCHF to a non-endemic country has been described in France in 2004(10).
The period during which transmission is highest is late spring?summer in the endemic zones of the countries mentioned. The number of suspected or confirmed cases in these endemic zones is therefore highly likely to increase in the coming weeks.
Notes and references
1)Throughout this document, "Kosovo" means Kosovo in accordance with Security Council resolution 1244 (1999).
2) Hoogstraal H. The epidemiology of tick-borne Crimean-Congo hemorrhagic fever in Asia, Europe, and Africa. J Med Entomol. 1979 May 22;15(4):307-417.
3) Kunchev A, Kojouharova M. Probable cases of Crimean-Congo-haemorrhagic fever in Bulgaria: a preliminary report. Euro Surveill. 2008;13(17):pii=18845.
4) Antoniadis A, Casals J. Serological evidence of human infection with Congo-Crimean hemorrhagic fever virus in Greece. Am J Trop Med Hyg. 1982 Sep;31(5):1066-7.
5) Antoniadis A, Alexiou-Daniel S, Malissiovas N, Doutsos J, Polyzoni T, LeDuc JW, et al. Seroepidemiological survey for antibodies to arboviruses in Greece. Arch Virol 1990 Suppl 1:277-85.
6) Papa A. Personal communication July 2008.
7) Bino S.. Joint WHO-MZCP Intercountry Workshop on Crimean-Congo Haemorrhagic fever (CCHF) Prevention and Control, Istanbul, Turkey 6?8 November 2006.
8) Dedushaj I., Joint WHO-MZCP Intercountry Workshop on Crimean-Congo Haemorrhagic fever (CCHF) Prevention and Control, Istanbul, Turkey 6?8 November 2006.
9) Pitches DW. Removal of ticks: a review of the literature. Euro Surveill. 2006;11(33).
10) Tarantola A, Nabeth P, Tattevin P, Michelet C, Zeller H. Incident Management Group.Lookback exercise with imported Crimean-Congo hemorrhagic fever, Senegal and France. Emerg Infect Dis. 2006 Sep;12(9):1424-6.
-
http://www.euro.who.int/surveillance...nterFriendly=1&
-------
11 August 2008
Crimean-Congo Hemorrhagic fever (CCHF) is a zoonosis transmitted by ticks that cause severe outbreaks in humans.
CCHF intensified activity and outbreaks constitute a threat to public health services because of its high case fatality ratio (10-40%), its potential for nosocomial transmission, and the difficulties in case management and prevention requiring a sustained multi-sectoral approach.
In the WHO European Region, CCHF is endemic in several areas of countries and territories south of the 50? parallel north.
In these areas, the peak of CCHF activity observed during late spring and summer.
Data available for 2008 indicate CCHF virus is circulating with particular intensity in Turkey, the Balkans, and southern districts of the Russian Federation.
The information summarised below was compiled thanks to the tireless support of EpiSouth - Network for Communicable Disease Control in Southern Europe and Mediterranean Countries.
It provides a focus on the epidemiology of CCHF in selected endemic countries and territories.
Additional details on CCHF in this and other WHO Regions are available on the EpiSouth web site.
1. Background
CCHF virus is a Nairovirus of the Bunyavirus family identified in 1956 in the Congo and in 1967 in what is now Uzbekistan.
CCHF virus is enzootic in the southern part of Europe (Balkans), Turkey, the southern Russian Federation, and in several countries in the Middle East, of sub-Saharan Africa, central Asia and the western part of China.
Reservoir:
Several species of ixodid ticks (mainly Hyalomma and Amblyomma) which are endemic to the semi-desert zones of a yet greater number of countries can transmit CCHF by bite.
Animals such as wild rodents and livestock serve as amplifiers.
Transmission:
The virus causes sporadic cases in humans, essentially linked to tick bites during farming or cattle-raising activities.
Clinical presentation:
In most cases, infection in humans causes few or no symptoms, although CCHF virus may cause a severe viral haemorrhagic fever. Person-to-person transmission to carers occurs, including in the health care setting.
Incubation:
1?7 days (on average 3?5 days).
Viraemia:
appears with clinical symptoms and lasts around 10 days.
Case-fatality rate (CFR)
The literature describes CFRs as high as 40?50%, especially in severe forms diagnosed during epidemics in resource-poor settings.
Global CFR in hospitalized patients (all grades of severity), however, is closer to 2?6% according to recent data collected in Turkey and the Russian Federation.
Data from South Africa or Turkey show that the CFR can be significantly higher in patients with biologically confirmed CCHF who present clinical and biological criteria of severity.
Non-specific supportive treatment may be effective.
WHO has approved ribavirin as a specific treatment, based on limited circumstantial data in the endemic setting and experimental evidence.
A vaccine has been developed in Bulgaria for use in humans.
Discrepancies in global CFR in hospitalized patients during epidemics may therefore be explained by differences in:
* the performance of surveillance systems in detecting less-severe cases; * the sensitivity and specificity of case definitions used and their positive predictive value during epidemics; and
* diagnostic and therapeutic management.
2. CCHF situation as of mid-2008: Turkey, Russian Federation, Bulgaria, Greece, Albania, and Kosovo(1)
2.1. Turkey
In 1974, seroepidemiological studies found evidence of anti-CCHF antibodies in 26 (2.4%) of 1100 sera tested in Turkey(2).
The first symptomatic human case of CCHF in Turkey was identified in 2002.
Between 2002 and 2007, the number of confirmed CCHF cases reported in Turkey regularly increased, especially in eastern and north-eastern rural areas (Table 1 and Fig. 1).
An epidemic is now reported each year in Turkey. It is most active from April to September.
Between 1 January and 30 June 2008, a total of 688 confirmed cases (with 41 deaths, CFR: 6.0%) have been reported in Turkey.
Cases are essentially described in adults exposed to tick bites during rural activities in north-central Anatolia.
Some sporadic cases occur in other areas of Turkey.
One case was described in Kirklareli (north-west of Istanbul) in 2007.
Since 2003, 8 cases have been documented in health care workers (HCW) (with 1 death) following accidental exposure to blood or body fluids.
In some instances (study protocols), cases were treated with ribavirin.
[Table 1. Confirmed CCHF cases and deaths in Turkey, 2002?2008 (Source: Ministry of Health) ]
[Fig. 1. Confirmed CCHF cases and deaths in Turkey, 2002?2008 (Source: Ministry of Health)]
2.2. Russian Federation
Data presented here originate from the Federal Service for Surveillance on Consumer Rights Protection and Wellbeing, Ministry of Health and Social Development of the Russian Federation (Rospotrebnadzor).
Cases are described each year in the Southern Federal District (okrug).
Cases occur mainly in 3 of the 13 zones of this District: Republic of Ingushetia, Rostov oblast and Stavropol kraj.
The number of cases reported has risen progressively since 2002 (Table 2).
A total of 839 confirmed cases (with 27 deaths) has been recorded since 2002.
The yearly CFR in confirmed cases ranges from 1.7% to 11.1% with a global CFR of 3.2% for the period 2002?2008 (based on preliminary data for 2008).
[Table 2. Confirmed CCHF cases and deaths in the Southern Federal District, Russian Federation, 2002?2008 (Source: Rospotrebnadzor) ]
[Fig. 2. Confirmed CCHF cases and deaths in the Southern Federal District, Russian Federation, 2002?2008 (Source: Rospotrebnadzor) ]
2.3. Bulgaria
Some areas of Bulgaria are endemic for CCHF. On average, 10?15 cases are reported each year.
The most significant epidemic in the country occurred in 1954?1955 with a total of 487 cases (213 in 1954 and 274 in 1955). Approximately 300 of these cases were reported in the Shumen district, in the north-east of the country.
Between 1953 and 1974, a total of 1101 CCHF cases were notified in Bulgaria (CFR 17%), of which 20 were acquired during health care.
Between 1975 and 1996, the development and distribution of a human vaccine was associated with a reduction in notified cases: 271 cases (CFR: 11.4%).
Since 1997, a total of 196 suspect or confirmed cases were notified (43 deaths, CFR: 22%) (Fig. 3).
[Fig. 3: Suspect or confirmed CCHF cases in Bulgaria, 1997?2008* (Source: National Centre of Infectious and Parasitic Diseases) ]
Between March 20 and July 10, 2008, national authorities identified 7 cases of CCHF:
* 2 confirmed cases (acquired while delivering care) and 4 probable cases in Gotse Delchev county, Blagoevgrad district, in western Bulgaria(3).
* An additional probable case was identified in Sliven district.
2.4. Greece
Several seroepidemiological studies conducted in the 1970s and 1980s found evidence for the circulation of CCHF virus in Greece.
CCHF virus strain AP92 was isolated from ticks collected from goats in 1976 in Vergina village (80 km west of Thessaloniki). This strain seems to be low or not pathogenic to humans.
The virus was found in 4 (6.1%) of 65 residents of Vergina village (where strain AP92 was isolated)4 and 1.1% of over 3000 sera from apparently healthy individuals, mainly farmers and shepherds, sampled throughout Greece (0?6.2%, depending on the region)(5). The observation of higher sero-prevalence in departments close to Vergina village (Pella, Imathia, Karditsa), combined with the absence of CCHF cases, suggests that the detected antibodies were most probably against AP92 strain, which is genetically different from all other CCHF viral strains(6).
The first symptomatic case of CCHF diagnosed in Greece was confirmed in a woman who died on 25 June 2008. She was exposed to tick bite during farming activities in rural areas near Komotini (Rhodope department in the Thrace region).
Tick control measures have been implemented and the surveillance of humans has been strengthened. Surveys on humans, domestic animals and ticks have been started. There are no other identified cases to date.
2.5. Albania
The first human case of CCHF was described in Albania in 1986.
A total of 35 suspect or confirmed cases were reported between 1986 and 1990(7).
From 2001 to 2006, a yearly average of 10 suspect and 5 confirmed cases have been reported (Table 3).
[Table 3: Suspect and confirmed cases of CCHF in Albania, 2001?2006 (Source: Public Health Institute) ]
Most cases are reported in Kuk?s district, in the north-eastern part of the country, although cases are regularly reported from other areas.
Anti-CCHF antibodies were found in 1.3% of 233 sera sampled in the general population.
2.6. Kosovo
The first human cases were described in 1954 during an epidemic with 8 cases.
[Table 4 presents data on suspect and confirmed cases of CCHF between 1995 and November 2006. ]
Available data indicate a seroprevalence of around 24% in the general population living in endemic areas (centre and south-western areas).
[Table 4. Suspected and confirmed CCHF cases in Kosovo, 1995?2006 (Source: Institute of Public Health(8)) ]
3. Comments
CCHF virus is the causative agent of the viral haemorrhagic fever with the widest geographical area of circulation in the world. Among other areas, it is present in the WHO European Region (Greece, Bulgaria, Turkey, Albania, Kosovo, southern part of the Russian Federation).
Evidence of CCHF circulation can also be found in most countries on the Black Sea coastline.
Low-intensity circulation of CCHF was established in Turkey and Greece over 30 years ago.
The virus has recently emerged on a larger scale in Turkey. This could be due to the multiplication of vectors and reservoir animals (hares, boars) in rural areas. Temperature changes may also play a role.
Data collected in Turkey and the Russian Federation show lower CFRs than those initially documented in endemic settings. This is due to the quality of diagnostic and medical management of cases, and to a sensitive system of detection through systematic screening of people referred for tick bites in endemic areas.
Some continue to debate the usefulness of ribavirin treatment in the early stages of infection.
In all countries concerned, the vast majority of cases is reported in known endemic areas. The occurrence of human CCHF cases, even in clusters, with a documented exposure to tick bites or to blood or body fluids of confirmed or suspect cases, is not an unexpected event and does not require specific measures other than those implemented by national authorities and informing tourists of available preventive measures.
Simple precautions can be observed to prevent tick bites (repellents, wearing long garments, careful removal of ticks using forceps in case of bite)(9).
No case has been reported in a tourist visiting any of the countries discussed here.
To date, a single case of imported CCHF to a non-endemic country has been described in France in 2004(10).
The period during which transmission is highest is late spring?summer in the endemic zones of the countries mentioned. The number of suspected or confirmed cases in these endemic zones is therefore highly likely to increase in the coming weeks.
Notes and references
1)Throughout this document, "Kosovo" means Kosovo in accordance with Security Council resolution 1244 (1999).
2) Hoogstraal H. The epidemiology of tick-borne Crimean-Congo hemorrhagic fever in Asia, Europe, and Africa. J Med Entomol. 1979 May 22;15(4):307-417.
3) Kunchev A, Kojouharova M. Probable cases of Crimean-Congo-haemorrhagic fever in Bulgaria: a preliminary report. Euro Surveill. 2008;13(17):pii=18845.
4) Antoniadis A, Casals J. Serological evidence of human infection with Congo-Crimean hemorrhagic fever virus in Greece. Am J Trop Med Hyg. 1982 Sep;31(5):1066-7.
5) Antoniadis A, Alexiou-Daniel S, Malissiovas N, Doutsos J, Polyzoni T, LeDuc JW, et al. Seroepidemiological survey for antibodies to arboviruses in Greece. Arch Virol 1990 Suppl 1:277-85.
6) Papa A. Personal communication July 2008.
7) Bino S.. Joint WHO-MZCP Intercountry Workshop on Crimean-Congo Haemorrhagic fever (CCHF) Prevention and Control, Istanbul, Turkey 6?8 November 2006.
8) Dedushaj I., Joint WHO-MZCP Intercountry Workshop on Crimean-Congo Haemorrhagic fever (CCHF) Prevention and Control, Istanbul, Turkey 6?8 November 2006.
9) Pitches DW. Removal of ticks: a review of the literature. Euro Surveill. 2006;11(33).
10) Tarantola A, Nabeth P, Tattevin P, Michelet C, Zeller H. Incident Management Group.Lookback exercise with imported Crimean-Congo hemorrhagic fever, Senegal and France. Emerg Infect Dis. 2006 Sep;12(9):1424-6.
-
http://www.euro.who.int/surveillance...nterFriendly=1&
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