VIRAL INFECTION
VIRL INFECTIONViruses :- are obligatory intracellular parasites , composed structurally of a central core of nucleic acid & a protective coat ( capsid) & in certain groups of an outer envelope .Tow main groups of viruses are distinguished DNA (parvo , papova , adeno , herpes , & pox virus) , & RNA viruses ( picorna , toga , ortho , reo …etc) .
HERPES VIRUS
Herpes virus :- a double stranded DNA virus that replicate in the nucleus , it produce a latent life long infection which may be intermittently clinically apparent . Viruses of this group are :- Herpes simplex virus type 1 & 2 . Epstein-Barr virus . Cytomegalo virus . Varicella-zoster virus . Human herpes 6 , 7 , 8 (kaposi sarcoma associated ) .HERPES SIMPLEX ( HSV )
HSV infection are caused by 2 different types (HSV 1 &2 ), HSV-1 is generally but not always associated with oral infection & HSV-2 with genital infection . Both types produce identical pattern of infection , virus passes through 2 phases :- Primary phase :- after which the virus become established in the nerve ganglion . Secondary phase :- charac. By recurrent disease at the same site . Genital type recur more frequently than the labial type .ORO-LABIAL HERPES INFECTION
Primary infection ( gingivo stomatitis & pharyngitis ) are the most frequent manifestation of first episode infection . Virus may spread either by :- Droplet infection . Direct contact . Saliva or cervical secretion from patient with no evidence of active infection .It occurs most commonly between the age 1-5 years , charac by more sever prodromal symptoms ( localized pain , tender lymphadenopathy , fever , generalized ache , headache ) than in the recurrent disease which take about 12-24 hours . Incubation period 3-12 days . Clinically there is grouped vesicles on erythematous base which subsequently erode . Lesions last 2-6 weeks unless secondarily infected . Recurrent infections :- predisposing factors are Local skin trauma (UV light exposure , chapping , abrasion ) . Systemic changes ( mense , fatigue , fever )
These factors reactivate the virus which then travel down the peripheral nerve to the site of initial infection & causes recurrent infection . Prodromal symptoms is less sever & last about 2-24 hours . Skin lesion chara. by grouped vesicles on erythematous base which take about 10 days to heal . Treatment :- it is a self limiting disease we treat to relieve discomfort & promote healing . Non-specific topical agent :- these include cool compresses , lubricating cream . Specific topical treatment:- penciclovir cream, acyclovir cream. These drugs shorten episode of herpes labialis by few hours or aday. Systemic treatment :-
This drug ( acyclovir ) :- Decrease new lesion formation . Decrease duration of viral excretion . Promote rapid healing . Subsequent recurrence rate not influenced by acyclovir .
acyclovir
famciclovirvalacyclovir
First episode
200 mg 5times/day for 7-10days
250mg tid for7-10 days
1gm bid 7-10days
Episodic, recurrent intermittent therapy
200 mg 5times/day for 5 days
125mg bid for 5 days
500mg bid for 3days
Clinical types of primary infection
Herpetic gingivostomatitis. Herpetic kerat conjuctivitis. Herpetic whitlow. Primary HSV-1 genital. Eczema herpeticum.VARICELLA
A highly contagious viral infection caused by VZV . Transmission is by air droplet or contact with vesicular fluid . Patient are contagious 2 days before appearance of the rash , until all the lesion have crusted . Incubation period 9-21 days , average 14 days . One attack give life long immunity . Clinically charac. By prodromal symptoms mild or absent in children & sever in adult , the rash is polymorphic ( in all stage of evolution ) it start as red papule then vesicle then crusted lesion , every lesion took about 24 hours , it is mainly trunkal distribution , mucus membrane could be affected .VARICELLA
Complication :- Skin :- secondary bacterial infection . Neurological :- encephalitis , Reye`s syndrome . Respiratory :-pneumonia . Liver :-hepatitis . Mild thrombocytopenia . Treatment :- It is a self limiting disease , only symptomatic treatment . Antipyretics,for pruritis such as bland antipruritic agent & antihistamine . Antibiotic if there is secondary bacterial infection , acyclovir for immunosuppres & adult .
HERPES ZOSTER (Shingles )
acute viral infection generally involving the skin of a single dermatome . People at all ages are affected , but incidence increase with age . Etiology :- HZ result from reactivation of varicella virus that entered the cutaneous nerve during episode of chicken pox , traveled to the dorsal root ganglia & remain in a latent form. Predisposing factors ( these factors increase severity but not incidence ) these include :- increasing age , immunosuppressive drugs , lymphoma , fatigue , emotional stress , & radiation therapy .HERPES ZOSTER
Clinically it passes through 2 phases :- Pre eruptive pain (pre herpetic neuralgia ) :- pain precede rash by 4-5 days either as itching or burning localized to the dermatome . Pre eruptive tenderness , hyperesthesia is a useful predictive sign . Eruptive phase :- in which there is successive crops of vesicles on erythematous base continue to appear for 7 days localized to a single unilateral dermatome , dermatome up & down could be affected , it take about 2-3 weeks to clear up .HERPES ZOSTER
Syndrome of herpes zoster :- Ophthalmic zoster :- ophthalmic branch of trigeminal nerve . Ramsay-Hunt`s syndrome :- geniculate ganglion . Sacral zoster :- S2 , S3 , S4 dermatome causing urinary retention , hesitancy or neurogenic bladder . Treatment:- Topical therapy :- wet compresses . Systemic therapy :- analgesic to relieve pain of acute herpetic neuralgia & nerve block carbamazepin &amitryptilin. Systemic antiviral :acyclovir in a dose 800 five times daily for 7-10 days to decrease pain . It is more effective when started in the 1st 48 hours of infection .MOLUSCUM CONTAGIOSUM
A common benign viral disease of the skin & mucus membrane caused by DNA pox virus . Incubation period 2-7 weeks . Mode of transmission :- primarily by person to person spread & sexually transmitted in adults & sexual abuse in children . Clinically charac. by a pearly to flesh colored papule dome shaped with central umblication , any site could be affected except palm & sole , & +ve koebner phenomenon .MOLLUSCUM CONTAGIOSUM
Treatment :- most of the lesions are self limiting & clear spontaneously ; 6-9 months & treatment must be individualized Curretage with or without anesthesia . Cryotherapy . Tretinoin therapy . Salicylic therapy . Laser therapy for genital lesion with CO2 laser .WARTS ( VERRUCAE )
A benign epithelial proliferation of the skin & mucus membrane that result from infection with human papilloma virus (HPV ) . These viruses do not produce acute signs & symptoms , but induce slow growing lesions that can remain latent or sub clinical for long period of time . Incubation period is between 2 weeks – 9 months average 2 months . Etiology :- HPV which is DNA virus . More than 80 different genotypes of HPV have been identified by recombinant DNA technology . Mode of transmission :- by direct contact in to a viable epidermis through a defect in the epithelia ( trauma or micro trauma ) .