Common Viral Infections: Influenzaviruses and Herpesviruses

Tintinalli: Chapter 143

Dave Piatt

Influenza A & B Antigenic drift

Minor mutations of the H or N molecule Antigenicity changes with mutations Causes annual epidemics (usually type A)

Antigenic shift New virus produced by genetic reassortment within a

host infected by two different influenzaviruses Population lacks immunity against new virus Causes major flu pandemics (such as in 1918)

Influenza Epidemiology

Occurs Nov. thru April in the U.S. Occurs year-round in the tropics

Spread via droplets produced during cough Incubation period is 2 days Viral shedding (contagiousness) starts 24

hours before onset of symptoms

Influenza Clinical features (onset is usually rapid)

Fever (38.6o – 39.8o) for 2-4 days Chills/rigor Headache Myalgias Malaise Cough Rhinorrhea Sore throat

Elderly often do not have classic symptoms and may have only fever, malaise, confusion, and congestion

Influenza Diagnosis

Clinical diagnosis during outbreak has an accuracy of about 85%

Rapid antigen tests Decrease empirical antibiotics Sensitivity 57-81% Specificity 93-100%

Influenza Complications

Pneumonitis Flu symptoms progressing to cough and dyspnea Hypoxia Bilateral infiltrates on CXR similar to ARDS Supportive treatment

Secondary Pneumonia Occurs 1-2 weeks after flu Treat with broad spectrum antibiotics and pulmonary support

COPD, Reye syndrome (with aspirin use), croup, myocarditis are also complications

Influenza Treatment

Amantadine and rimantadine (100 mg BID X 5 days) Approved for type A only; not active against type B If started within 48 hours of onset of symptoms, it can

reduce duration of symptoms by 1-2 days Avoid in pregnancy Approved for children over 1 year of age

Oseltamivir and zanamivir (Tamiflu and Relenza) Active against types A & B Reduces duration of symptoms by 1 day if started within 48

hours of onset of symptoms

Influenza Prophylaxis

Annual formulation contains 2 strains of type A and 1 strain of type B

70-90% effective in those under age 65 Recommended for all persons over age 65, residents of

chronic care facilities, patients with chronic cardiopulmonary disease, diabetes, metabolic disease, or renal disease; immunosuppressed patients, and healthcare workers

Safe for pregnant/lactating women Anti-influenza medicines are 75-90% effective in preventing

influenza if given as a 6-8 week course during peak flu season

Herpesviruses Dwell in host as a lifelong latent infection May cause clinical disease at a time distant from

the primary infection Some are carcinogenic Varicella-zoster virus (VZV) is spread via

aerosolized particles and close contact Herpes simplex virus (HSV) and Epstein-Barr

virus (EBV) transmission occurs during asymptomatic shedding

Herpes Simplex 1 & 2 Epidemiology

Transmitted via infected secretions on mucous membranes or open skin

HSV-2 is primarily transmitted sexually

Herpes Simplex 1 & 2 Oral HSV

Primarily HSV-1, but can be HSV-2 Primary lesion lasts 1-2 weeks Lesions recur in 60-90% of infected people Recurrences triggered by local trauma, illness, or

stress Treatment: acyclovir 400 mg PO 5 times/day (topical

acyclovir is ineffective) Prophylaxis: oral acyclovir reduces outbreaks by

50-75% in those with frequent/severe outbreaks

Herpes Simplex 1 & 2 Genital HSV

Majority caused by HSV-2 Covered in chapter 141 (STDs)

Ocular HSV Usually HSV-1 Ulcerative keratitis is most common manifestation.

May lead to corneal blindness Vesicles may be seen on the conjunctiva or lid Fluorescein stain may show corneal dendritic ulcers Ophthalmologic consultation is imperative, and patient

may need to be admitted for IV acyclovir

Herpes Simplex 1 & 2 Encephalitis

Usually HSV-1 Temporal lobes are the major target and lesions may be

seen on CT and MRI Presents as headache, fever, and altered mental status with

preceding viral-like illness. Patients may have olfactory hallucinations

CSF findings: elevated WBCs with mononuclear predominance

Empirical treatment with IV acyclovir at 10 mg/kg every 8 hours should be initiated if suspicion exists

If untreated, mortality rate is 70%

Herpes Simplex 1 & 2 Bell Palsy

Usually HSV-1 Causes palsy of the peripheral branch of CN VII Presents as facial hemiplegia or hemiparesis, taste

disturbance, decreased blinking, dry eyes, facial numbness, and jaw/face pain

Central CN VII lesions spare the forehead but cause unilateral lower facial weakness. Peripheral lesions result in forehead paralysis. Attempting to close the eye on the affected side results in an upward gaze (Bell phenomenon)

Herpes Simplex 1 & 2 Bell Palsy

Examination of the ear, tympanic membrane, mastoid, and parotid gland should be normal

Bell palsy with otitis media, mastoiditis, or parotitis is an ENT emergency

Vesicles on the TM or canal is diagnostic of Ramsay Hunt syndrome

Differential includes stroke, tumor, atypical Guillain-Barre, and Lyme disease

Treatment: prednisone 60 mg PO X 5 days with acyclovir 400 mg 5 times/day for 10 days

Eye care with artificial tears is the most important therapeutic intervention made by the ED physician

Herpes Simplex 1 & 2 Herpetic Whitlow

HSV infection of the finger (usually one digit) HSV-1 is seen in children who self-inoculate during an

episode of oral herpes and in health care workers (dentists)

HSV-2 more common if digital/genital contact Very painful and accompanied by axillary adenopathy Vesicles contain necrotic epithelial cells, not pus. If

confused with paronychia and the finger is incised, delayed healing and secondary infection may occur

Spontaneously heals in 2-3 weeks, may use acyclovir

Herpes Zoster: Chickenpox HZV is human herpesvirus 3 Primary infection is chickenpox Reactivates later as zoster (shingles) Epidemics occur late winter/early spring Spread via respiratory droplets Patients are infectious 48 hours before rash

appears until the vesicles have crusted over Rash appears 14 days after exposure. The virus

becomes latent in a dorsal root ganglion

Herpes Zoster: Chickenpox Clinical features

Prodrome of 1-2 days of fever, malaise Clear vesicles on an erythematous base appear on the face

and trunk, then spread centripetally to the extremities. New lesions will appear and the old ones will become turbid and scab over. The hallmark of chickenpox is vesicular lesions in various stages

Complications can include encephalitis, cerebellar ataxia, pneumonitis, and Reye syndrome

Mortality rate among adults is 15 times higher than in children

Chickenpox during pregnancy can cause fetal abnormalities

Herpes Zoster: Chickenpox Treatment

Over age 12 Acyclovir 800 mg PO QID X 5 days started within 24 hours of

onset of rash Neonates of mothers who developed chickenpox 5 days before

delivery or within 48 hours postpartum Varicella-zoster immune globulin (VZIG) to confer passive

immunity Patients with varicella encephalitis, pneumonitis, or who are

immunocompromised should be admitted for IV acyclovir Varicella vaccine recommended for children over age 1 year. It

is a live vaccine and is contraindicated in immunocompromised patients and in pregnant/lactating women

Herpes Zoster: Shingles Is a reactivation of latent VZV infection Lifetime incidence of 20%, usually in elderly Lesions limited to a single dermatome, usually

thoracic or lumbar Begins as a prodrome of pain for 1-3 days in the

affected area, followed by a maculopapular rash that progesses to vesicles

Disease course is 2-4 weeks Disseminated disease can cause pneumonitis,

hepatitis, or meningoencephalitis

Herpes Zoster: Shingles Complications:

Herpes zoster ophthalmicus (HZO) Involves the ophthalmic branch of CN V Vision-threatening Hutchinson sign (lesion of tip of nose) may be

seen before ocular involvement May also see a dendriform corneal ulcer with

fluorescein staining Mandatory ophthalmologic consult

Herpes Zoster: Shingles Complications:

Ramsay Hunt syndrome Involves the geniculate ganglion of CN VII Presents with facial palsy, unilateral weakness, loss

of taste, and ear canal or TM vesicles May also see intraoral lesions May be a cause of mental status change in elderly Presentation and treatment are similar to Bell palsy Admit immunocompromised patients for IV

acyclovir

Herpes Zoster: Shingles Complications:

Postherpetic neuralgia Most common complication Occurs in 10-20% of all shingles cases, and in

70% of patients over age 70 Resolves in 1-2 months First-line treatment is systemic analgesics; second-

line treatment is amitriptyline or carbamazepine Corticosteroids improve quality-of-life in elderly

Start 21-day taper at 60 mg PO daily

Epstein-Barr Virus: Infectious Mononucleosis Human herpesvirus 4 Spread by close contact, such as kissing Incubation period of 1-2 months, followed by

prodrome of malaise, fatigue, and fever Classic symptoms include fever, sore throat

(exudative pharyngitis), lymphadenopathy, splenomegally, and atypical lymphocytosis. Bilateral tender cervical adenopathy is universal

Hepatomegally and jaundice is common in adults

EBV: Infectious Mononucleosis Palpable splenomegally occurs in ½ of patients,

most prominent during week 2 of the illness The incidence of splenic rupture is 0.1-0.5% and

is generally at week 2-3 of the illness. Patients should be instructed to avoid contact sports and strenuous activity for 4 weeks

Complications of mono include hemolytic anemia, thrombocytopenia, encephalitis, meningitis, obstructive tonsillitis, and lymphoma

EBV: Infectious Mononucleosis Lab analysis may show elevated WBC with

increased atypical lymphocytes and monocytes Commercial tests (monospot) are 78-83%

sensitive and 98-100% specific. Patients with classic EBV symptoms and a negative monospot should have a repeat monospot in 1 week

Treatment is supportive. If penicillin is given to treat a suspected strep pharyngitis, 95% of patients will develop a rash

Cytomegalovirus Human herpesvirus 5 Causes a primary illness and then exists in a

latent state in the host until reactivation Found in milk, saliva, urine, semen, and cervical

secretions Also transmitted during blood transfusions and

bone marrow and organ transplantations One of the TORCH agents known to cause

intrauterine infections

Cytomegalovirus Infection is usually asymptomatic, but symptoms

can include fever, chills, myalgias, and headache. Fever may last for 1-5 weeks

May see atypical lymphocytosis, splenomegally, lymphadenopathy, and increased LFTs

Consider CMV in patients with mono-like symptoms but who are monospot negative

Cytomegalovirus 10% of AIDS patients develop CMV

retinitis, which causes floaters or decreased vision. Fundoscopic exam may show retinal hemorrhages or exudates. Without treatment, this will progress to blindness

Treat with IV ganciclovir or foscarnet

Cytomegalovirus CMV causes significant morbidity and

mortality in post-transplant patients Pneumonia is the most common infection Most common in bone marrow transplant

patients CMV should be considered for a fever

within 3 months of a transplant

Cytomegalovirus Treat CMV with ganciclovir or foscarnet Ganciclovir is approved for CMV retinitis in

AIDS patients and for CMV prevention in transplant patients

Foscarnet is used for resistant CMV infections or for patients unable to take ganciclovir

Neither medication cures patients of CMV, but they suppress the acute disease process

Questions 1. Bell palsy involves which cranial nerve?

A. CN IV B. CN V C. CN VI D. CN VII E. CN VIII

2. Which is false regarding influenza? A. The vaccine is unsafe in pregnancy B. Amantadine is effective against types A and B C. Complications of influenza include pneumonia, pneumonitis, and COPD

exacerbation D. The vaccine is 70-90% effective E. Antigenic drift causes annual epidemics

3. Incision of a herpetic whitlow vesicle will produce pus T or F?

4. Which of the following is false regarding EBV? A. Splenomegally is palpable in 90-100% of all patients with infectious mononucleosis B. Bilateral cervical adenopathy is nearly universal C. Virus is spread by close contact, such as kissing D. Atypical lymphocytosis is a common finding E. Treatment is primarily supportive

5. Retinitis in AIDS patients is usually caused by which virus? A. VZV B. EBV C. CMV D. HSV-1 E. HSV-2

Answers 1. D 2. B 3. False 4. A 5. C