ml7 viral infections

8/7/2019 ML7 Viral Infections

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Viral Infections

3rd Year Medicine Attachment



Over view

� Important viral infections in Malaysia

� Modes of transmission

� Clinical features of viral infections� Diagnostic methods

� Treatment

� Immunisation/ Disease control



Important viral infections in

Malaysia� Dengue fever

� Influenza

� Rabies� Japanese encephalitis

� Herpes encephalitis

� Infectious mononucleosis (EBV)

� Shingles (VZ)

� SARS



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



Dengue fever



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´)



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´



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%)



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.



Dengue fever

Disease control:

� Vaccine- under development

� Control A. aegypti by spraying anddestroying breeding grounds

� Education of the public



Influenza



Influenza

� Caused by influenza A and B viruses

� Seasonal epidemics

� Also causes pandemics� Antigenic drift

� Transmission person-to-person by dropletinfection

� Short incubation period



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



Influenza

Treatment

� Anti-virals

� Supportive care

Prophylaxis

� Vaccine changed yearly

� Elderly, respiratory/heart patients andhealthcare workers should be vaccinated



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



Rabies



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



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



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.



Rabies

Prevention

� Pre-exposure vaccination

� Vaccinate dogs� Regular dog-catching

� Quarantine and licensing

� Very common in Thailand- ³immune-belt´in Malaysia¶s Northern states



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




Clinical features

� Fever, headache, vomiting

� Seizures, reduced conscious level

� Variety of pyramidal and extrapyramidal features

Treatment

� Supportive

� Effective vaccine available (not for Nipah)



Herpes encephalitis



Herpes encephalitis

� Caused by HSV-1

� Treatable cause of viral encephalitis

� Relatively rare

Clinical features

� Fever, headache, drowsiness� Focal neurological signs, seizures, coma



Herpes encephalitis

Diagnosis

� CT/ MRI, EEG

� Serology blood/CSF

Treatment

� Supportive

� IV acyclovir (give even if HSV notconfirmed)



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)




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.



Shingles



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



Shingles

Clinical features

� Prodromal pain and tingling

� Characteristic vesicles, dermatomal distribution

� Post-herpetic neuralgia

Treatment

� Topical preparations� Oral acyclovir

� Prednisolone



SARS



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



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



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



Any questions?

ml7 viral infections

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