VIRAL HEMORRHAGIC FEVER OUTBREAKS
Introduction:
Viral Hemorrhagic Fevers are a multi-system syndrome caused by four distinct families BSL-4 RNA viruses.It causes severe vascular damage usually accompanied by serious life threatening symptoms like bleeding. VHFs are usually endemic and are spread to other regions only when the host is exported(CDC,2018). Figure 1 shows the diseases caused by the family of viruses, their origin and vector. Outbreaks caused by these viruses are usually irregular and sporadic. Some of these fevers are as severe as Ebola , whereas some of them are not fatal.Among the several VHF, four notable fevers can be imported to Australia they are :Lassa fever, Crimean-congo, Marburg and Ebola (Department of Health & Human Services, 2015).
Figure 1: Classification of Viral Hemorrhagic Fever Viruses, their distribution and diseases caused by them.(Borio et al., 2002)
In this report the history and some of the notable past outbreaks of non-Ebola diseases like, CCF, Lassa fever and Marburg fever will be briefly discussed. This report will also cover about how these diseases differ from that of Ebola fever, including the severity and symptoms of these diseases.
CRIMEAN -CONGO FEVER
Crimean-Congo fever is caused by Nairovirus. It is a tick borne disease, with Hyalomma genus ticks being major vectors(WHO,2013). Figure 2 displays the geographic distribution of CCHF, color coded based on severity of the disease.
This arboviral disease was first identified in crimean, 1944 and later recognized in Congo in 1969, hence the name. The first human infection was reported in the year 1976.An outbreak of both CCF and dengue was reported in the year 2010 in Pakistan , around 1500 cases were recorded (Zeller et al. 2007)
Most of the symptoms like fever, abdominal pain, vomiting, muscle pain, fatigue , uncontrolled bleeding(hemorrhage) are common to that of Ebola, while symptoms like flushed face, sensitivity to light, red throat, petechiae on palate, red eyes are characteristic to that of CCHF.(CDC,2013).Death usually occurs after 14 days from the onset of symptoms. The case fatality rate is 40%. The antivirus drug, Ribavirin is effective in most cases.
Figure 2: Geographical Distribution of Crimean-Congo Fever ( WHO,20
LASSA FEVER
Lassa fever is a zoonotic disease usually transmitted by ingestion or inhalation of virus excreted in urine of the multimammate rat, which is a wide spread vector.
It was first identified in the year 1969 in Lassa , Nigeria . The index case was an American missionary nurse.Since 2000, there have been 25 outbreaks of this disease. The recent unprecedented outbreak has sickened 365 people and killed 81 since 1st of January 2018 (Maxmen, A., 2018). Figure 3 shows the Outbreak distribution map for Lassa fever.
Unlike Ebola fever, 80% people experience mild symptoms like fever, weakness, headache and remaining 20% experience serious symptoms like hemorrhage, pains, respiratory distress and neurological problems. Deafness is a common symptom in about 25% patients usually persistent for about 1-3 months after cure sometimes maybe permanent.Excretion of protein in urine is also observed. Death rate. In third trimester is usually high with spontaneous abortion. Ribovirin is found to be effective during early stage.(CDC,2015)
MARBURG:
Marburg is a rare, zoonotic fever caused by Marburg virus of Filoviridae family same as that of Ebola virus. The vector is cave dwelling fruit bats of genus Rousettus aegyptiacus.
First identified in the year 1967 when the German Institute of Marburg was doing polio research using a monkey from Uganda which resulted in the death of 7 people.Since then 12 outbreaks were observed across the sub Saharan Africa resulting in almost 400 deaths.After the 1998 outbreak in the Democratic Republic of Congo (mortality 83%) , Marburg outbreak in Angola was declared as the worst outbreak killing almost 227 people,90% mortality(WHO,2017).Figure 3 shows the Outbreak Distribution of Marburg Fever.
Figure 3: Outbreak Distribution map (CDC, 2014)
The incubation period is usually 5-10 days. Symptoms like Maculopapular rash, myalgia, ghost like features along with common symptoms like fever, hemorrhage, shock, headache, jaundice are observed.The case fatality rate is 80%. There is no effective treatment similar to that of Ebola fever.(CDC, 2014)
Contrast to Ebola:
Except for Marburg fever other VHFs are not as severe as Ebola. Unlike other Viral Hemorrhagic fevers, the origin of Ebola fever and vector for transmission is not know. Ebola virus is found to be persistent in immune-privileged sites even after recovery in some people (who).The antibodies to Ebola virus is observed to be persistent for about 10 years after infection (CDC). Case fatality rate has been increased to 90%.
Conclusion:
Most of the Viral Hemorrhagic fevers are fatal and the severity of the disease varies in many aspects like incubation period, mode of transmission, etc. Most of the VHF’s can be treated. The non-Ebola fevers differ from that of Ebola fever in terms of symptoms, for example CCHF causes petechiae, Lass fever causes deafness and abortion, Marburg causes Macculopapular.
References
1)Borio, L., Inglesby, T., Peters, C., Schmaljohn, A., Hughes, J., Jahrling, P., Ksiazek, T., Johnson, K., Meyerhoff, A., O’Toole, T., Ascher, M., Bartlett, J., Breman, J., Eitzen, Jr, E., Hamburg, M., Hauer, J., Henderson, D., Johnson, R., Kwik, G., Layton, M., Lillibridge, S., Nabel, G., Osterholm, M., Perl, T., Russell, P., Tonat, K. and for the Working Group on Civilian Biodefense, 2002. Hemorrhagic Fever Viruses as Biological Weapons. JAMA, 287(18), p.2391.
CDC, n.d ,Virus Families| Viral Hemorrhagic Fever (MHF) | CDC, viewed 13 April 2018 ,<https://www.cdc.gov/vhf/index.html>
Department of Health & Human Services, 2015, State Government of Victoria, viewed 15 March 2018, < https://www2.health.vic.gov.au/public-health/infectious-diseases/disease-information-advice/viral-haemorrhagic-fever>
Maxmen, A., 2018, Deadly Lassa-fever outbreak tests Nigeria’s revamped health agency,Nature News, viewed 16 March 2018, < https://www.nature.com/articles/d41586-018-03171-y>
Aradaib, I., Erickson, B., Mustafa, M., Khristova, M., Saeed, N., Elageb, R. and Nichol, S 2018, ‘ Nosocomial Outbreak of Crimean-Congo Hemorrhagic Fever, Sudan’.
World Health Organization , n.d ,Fact Sheets, viewed 14 April 2018, <http://www.who.int/mediacentre/factsheets/en/>
World Health Organization, 2017. Geographical Distribution of Crimean-Congo Hemorrhagic Fever. [image] ,viewed 15 April 2018,<http://www.who.int/emergencies/diseases/crimean-congo-haemorrhagic-fever/Global_CCHFRisk_2017.jpg>