ml7 viral infections
TRANSCRIPT
8/7/2019 ML7 Viral Infections
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Viral Infections
3rd Year Medicine Attachment
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Over view
� Important viral infections in Malaysia
� Modes of transmission
� Clinical features of viral infections� Diagnostic methods
� Treatment
� Immunisation/ Disease control
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Important viral infections in
Malaysia� Dengue fever
� Influenza
� Rabies� Japanese encephalitis
� Herpes encephalitis
� Infectious mononucleosis (EBV)
� Shingles (VZ)
� SARS
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More viral infections in Malaysia
� Viral hepatitis
� Human Immunodeficiency Virus
� Viral gastroenteritis (rotavirus)
� Oral / genital Herpes
� Cytomegalovirus
� Measles
� Mumps� Rubella
� Hand-foot-and-mouth disease
Mainly affect children
Not serious unless
immunocompromised
Covered in other lectures
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Dengue fever
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Dengue fever
� Caused by Dengue virus 1-4 (flavivirus)
� Aedes aegypti mosquito is vector
� May be asymptomatic or non-specific
illness or classical syndrome
� Classical syndrome= fever, rash, severemyalgia (³breakbone fever´)
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Dengue Haemorrhagic fever
Pathogenesis:
� Possibly caused by immune response toreinfection with different strain of virus
4 Clinical Criteria:
� Fever
� Haemorrhagic manifestations
� Low platelet count
� Evidence of ³leaky capillaries´
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Dengue Shock Syndrome
Warning Signs:
� Abdominal pain - intense and sustained
� Persistent vomiting
� Abrupt change from fever to hypothermia, withsweating and prostration
� Restlessness or somnolence
Progression:� Circulatory failure, shock, multi-organ failure,
death (15%)
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Dengue Haemorrhagic fever/
Shock SyndromeDiagnosis:
� Clinical (NB tourniquet test non-specific)
� FBC, U+E, LFT, albumin, urinalysis
� Virus isolation (first 3 days)
� Serology (convalescence)(IgM antibody &IgGAntibody)
� Fever more than 15 days Dengue is ruled out
� Haemoglobin is normal or above where as in thefollowing diseases anemia is common- Malaria ,Typhoid,&Leptospirosis
Treatment:
� Supportive
� Hospitalise if haemorrhagic manifestations, dehydratedor warning signs present
� AVO
ID intramuscular injections.
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Dengue fever
Disease control:
� Vaccine- under development
� Control A. aegypti by spraying anddestroying breeding grounds
� Education of the public
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Influenza
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Influenza
� Caused by influenza A and B viruses
� Seasonal epidemics
� Also causes pandemics� Antigenic drift
� Transmission person-to-person by dropletinfection
� Short incubation period
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Influenza
Clinical features
� Fever, headache, myalgia, malaise
� Upper respiratory tract symptoms
� Can progress to pneumonia and multi-organfailure (in high-risk patients)
Diagnosis
� Rapid diagnostic tests available
� Serological tests more sensitive
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Influenza
Treatment
� Anti-virals
� Supportive care
Prophylaxis
� Vaccine changed yearly
� Elderly, respiratory/heart patients andhealthcare workers should be vaccinated
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Avian Influenza
� Caused by influenza A strain H5N1
� Current outbreak started Dec 2003
� Can be transmitted to humans (but stillrare in humans)
� Very aggressive in humans- usual flu +
early LRT symptoms + watery diarrhoea� Human disease in Cambodia, China,
Indonesia, Vietnam, Thailand, Turkey, Iraq
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Rabies
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Rabies
� Caused by Rhabdovirus (bullet-shaped)
� Reser voir in canines and bats
� Most human infections from dog bites
� Incubation period 2 weeks- 1 year
� More proximal bite/large innoculam-shorter incubation period
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Rabies
Clinical progression
� Virus ascends ner ves to CNS
� Fever, anxiety, insomnia, delusions,hallucinations may developaccompanied by spitting ,biting&mania with lucid inter val in whichpatient is markedly anxious.pain/paraesthesia at site of bite.
� Although patient feels thirsty attempt at drinking provoke violentcontractions of the diaphragm and other respiratorymuscles(Hydrophobia)
� More widespread spasms
� Cranial ner ve palsies develop and terminal hyperpyrexia is common
� Respiratory arrest
� Death ensures usually within a week of the onset of symptoms
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Rabies
Diagnosis
� CLINICAL
� Rapid immunofluorescent techniques can detect antigen in CORNEAL impression smears or skinbiopsies
� At post-mortem (to look for Negrie bodies)
Treatment
� Local treatment to wound� Supportive treatment- heavily sedated with Diazepam 10 mg 4- 6 hourly (iv), supplemented by
Chlorpromazine 50 -100mg if necessary.
� Nutrition and fluids by iv or through a gastrotomy.
� PRE EXPOSURE prophylaxis.Professionals handle potentially infected animals ,&those who workwith rabies virus in laboratories, live at special risk in rabies endemic areas.
� Protection is afforded by two intra dermal injections of 0.1ml Human diploid cell strain vaccine or two intramuscular injections of 1ml given 4 weeks apart followed by yearly booster.
� Post exposure prophylaxis-� Rabies can usually be prevented if treatment started within a day or two of biting, delayedtreatment may still be of value.
� For maximum protection Hyper immune serum and vaccine are required.
� Human diploid cell strain vaccine 1.0ml( im over deltoid region)on days 0,3, 7,14, 30&90 days.
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Rabies
Prevention
� Pre-exposure vaccination
� Vaccinate dogs� Regular dog-catching
� Quarantine and licensing
� Very common in Thailand- ³immune-belt´in Malaysia¶s Northern states
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Japanese encephalitis
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Japanese encephalitis
� Caused by a flavivirus
� Vectors are Culex mosquito (breeds in rice
fields)� Pig acts as amplifier host
� Common in Asia/Western Pacific� Previous Nipah virus outbreak in Malaysia,
1998
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Japanese encephalitis
Clinical features
� Fever, headache, vomiting
� Seizures, reduced conscious level
� Variety of pyramidal and extrapyramidal features
Treatment
� Supportive
� Effective vaccine available (not for Nipah)
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Herpes encephalitis
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Herpes encephalitis
� Caused by HSV-1
� Treatable cause of viral encephalitis
� Relatively rare
Clinical features
� Fever, headache, drowsiness� Focal neurological signs, seizures, coma
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Herpes encephalitis
Diagnosis
� CT/ MRI, EEG
� Serology blood/CSF
Treatment
� Supportive
� IV acyclovir (give even if HSV notconfirmed)
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Infectious mononucleosis
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Infectious mononucleosis
� Caused by Epstein-Barr virus (EBV)
� Also called ³Glandular fever´
� Transmitted by saliva and aerosol
Clinical features-Triad=1.Sore throat
2.Hepato splenomegaly
3.LYMPHADENOPATHY(posterior cer vical)
� Fever, headache, malaise,
� Macular rash after ampicillin
� Mild hepatitis + other rare complications (spleenicrupture)
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Infectious mononucleosis
Diagnosis
� Atypical mononuclear cells on blood film
� Paul-Bunnell& Monospot test
� The heterophile antibody present during acute illness and convalescence and agglutinatesErythrocytes of sheep or Horse .It has a specific absorption pattern detected by Paul Bunneltitration test
� And slide test such as MONOSPOT test
� Acute infection is characterised by-� 1.Anti viral capsid (VCA)antibodies in the IgM class.
� 2.Antibodies to EBV early antigen (EA)
� 3.Absent antibodies to EBV nuclear antigen(anti-EBNA)
Treatment
� Nil specific
� Steroids if neurological involvement� Aspirin gargles to relieve sore throat and if throat culture yields Beta hemolytic streptococcus a
course of Erythromycin can be given.
� When pharyngeal edema is severe Prednisolone 30 mg a day for 5 days is suggested.
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Shingles
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Shingles
� Caused by Varicella zoster virus
� Chicken pox is primary infection
� Virus remains latent in dorsal root andcranial ner ve ganglion
� Spread by direct contact and aerosol
� Infection reactivated in elderly/immunocompromised
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Shingles
Clinical features
� Prodromal pain and tingling
� Characteristic vesicles, dermatomal distribution
� Post-herpetic neuralgia
Treatment
� Topical preparations� Oral acyclovir
� Prednisolone
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SARS
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SARS
� Severe acute respiratory syndrome
� Caused by SARS coronavirus
� Outbreak in 2003
� Transmission by contact + ?airbourne
Clinical features
� Fev
er, headache, myalgia (2 days)� Dry cough, dyspnoea, hypoxia (3-7 days)
� Infiltrates on CXR
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SARS
Diagnosis
� Clinical
� Acute and convalescent serology
� Local and state labs for SARS Co-V testing
Treatment
� Supportive
� 10-20% require intubation and ventilation
� ?anti-virals
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Conclusion
� Most viral infections have mild and severe
forms
� Need to know clinical features and havehigh index of suspicion in endemic areas
� Treatment mostly supportive
� Anti-virals can help in some cases butneed to be given early
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Any questions?