VIRAL HAEMORRHAGIC FEVERS Year 4 Internal Medicine Notes

VIRAL HAEMORRHAGIC FEVERS Year 4 · Internal Medicine Collection: 4TH YEAR ALL NOTES / IMED / IMED 4.3 / MOGERE -- Slide 1 VIRAL HAEMORRHAGIC FEVERS Dr Alex Mogere Consultant Physician Slide 2 defn Clinical multisystem illness associated with fever and bleeding diathesis caused by several distinct families of viruses Symptoms may start as:fevr, malaise, headache, arthralgia, myalgia, abdominal pain, May progess to; h’ge, increased vascular permeability, hypotension and shock, multiorgan failure Slide 3 Causative viral groups Slide 4 Haemorrhagic fever viruses Slide 5 Virology of the VHF single stranded RNA enveloped Infectious during viremia stage Low infectivity dose- 1-10 viruses Ltd to where host lives- geographically Humans are not the natural reservoir, but accidentally infected when come in contact with infected hosts Human outbreaks are sporadic and irregular Slide 6 When human is infected can affect another human No established tx Best tx is infection control Role in bioterrorism- due to high morbidity and mortality High aerosol transmisiion of most except dengue fevr virus Slide 7 EPIDEMIOLOGY OF HFV DISEASE TRANSMISSION HFVS are zoonosis-arthropod vectors and rodents are main reservoirs A.Natural infection of humans Bite of infected arthropod-ticks/mosquitoes Aerosol from infected rodent excreta Direct contact with infected animals/carcasses or formites Slide 8 PATHOGENESIS The target organ is the vascular bed Intracellual replication of virus Cytokine release –hypotension/shock Thrombocytopenia Effect on BM and clotting factors Slide 9 Case fatality (mortality) rate Filoviruses- abt 90% for Ebola Flaviviruses- 0.5% Arenaviruses- 15-30% Causes of death: Hemorrhagic diathesis Shock Multiorgan failure Slide 10 DDX Slide 11 Filoviruses-EBOLA, MARBUG Category A bioweapon(bioterrorism) CDC 1999 Potential to cause widespread illness/death 1st appeared in Zaire and Sudan in 1976 Outbreak in 2013 in Guinea then Liberia, Sierra Leone, and Nigeria Virus transmission from wild animals/fruit bats/rodents Slide 12 Ebola virus disease transmission Direct humn to human contact- saliva, breastmilk, stool, skin, semen, Lab staff at risk Transmission thro semen may occur upto 5/52 after clinical recovery Indirect contact transmission via envt contaminated with such infected secretions Handling ill, dead infected chimps or other infected animals Hcws while attending pts Slide 13 Flaviviruses (n/b flavus in latin-yellow) A. Yellow fever B. Dengue fever C. OMSK HF D. Kyasanur Forest Disease Slide 14 Mode of transmission Yellow fever- Aedes mosquito() Dengue fever-Aedes mosquito-Aedes aedypti OMSK HF/Kyasanur- tick bite Slide 15 Yellow fever cycles Short incubation period-3-6/7 Initial symptoms- fever,chills, h/ache, Toxic phase- fevr with initial symptoms plus coagulopathy and h’ge, JN, hypotension, shock,metabolic acidosis, arrhythmias, confusion, seizures, shock, coma Jungle Urban intermediate Slide 16 Ct. Yellow fever Majority,no illness relative bradycardia with fevr Mortality rate 5-20%(20-50% in epidemics and hosp.pts) 90% of cases occur in Africa,10% S.America Vacinne available Live attenuated vaccine-single dose Immunity in 1 week in 95% of people Protection for 30-35 yrs No specific Tx available Slide 17 Dengue fever Endemic throughout Americas, Asia & Africa Vector-Aedes aegypti& aedes albopictus Virus replicates in mosquitoes Very rare by blood transmission, organs transplant & vertical transmission Incubation period 3-14 days The most prevalent mosquito-borne viral disease in the world 1/3 of the world populations are exposed Slide 18 Ct. Dengue fever 100 countries have endemic dengue transmission USA- 10.4% of post viral travel systemic febrile illness for travelers returning from endemic areas No available vaccine No specific Tx Slide 19 Dengue fever serotypes DEN 1,2,3 &4 All can cause severe illness/fatal infection No cross immunity after infection with one, but life long immunity to the same type More predisposition to DFS/DSS if infected by another serotype Complicated pathogenesis-partially due to ab-dependent enhancement Humans the main reservoir, though monkeys may be Slide 20 Symptoms of dengue fevr Slide 21 Clinical manifestations of dengue fever Undifferentiated fever Classic dengue fever Dengue hemorrhagic fever/DHF Dengue shock syndrome/DSS Slide 22 Classic dengue fever Acute febrile illness Severe h’ge- retro-ocular Myalgia, arthralgia N,V 50%, diarrhoea -30% Rash -50%(maculopaular, petechiae, erythematous) Slide 23 DHF Most serious of the forms WHO estimates 500,000 cases/yr Mortality,10 %, as jigh as 50 % WHO diagnostic criteria- fevr, h’gic manifestations- low plts(<100K/ml), evidence of leaky capillaries Slide 24 DSS WHO criteria for DHF and evidence of circulatory failure or shock Rapid, weak pulse, narrow pulse pressure(<20mmHg) Cold, clammy skin Altered mental status Slide 25 Bunyaviruses Rift valley fever Hantavirus Crimean Congo HF Viral hosts: arthropod vectors & rodents Mosquitoes-