Viral Infections
  • Infectious Mononucleosis (Glandular Fever)

This is a viral infection of the lymph nodes, usually seen in adolescents

– The virus is transmitted by saliva (kissing disease) and infects squamous epithelia cells of oropharynx before spreading elsewhere in the body

– It can then affect the liver giving hepatitis and also B cells

– This can give rise to a lymphocyte leucocytosis of CD8+ T cells

Cause:  Epstein Barr Virus infection (90%), Cytomegalovirus

 

Symptoms: Sore throat, fever and large lymph nodes

– Splenomegaly –> increased risk of splenic rupture

– Hepatitis and potential jaundice –> virus infects hepatocytes

– A pruritic rash in patients who take ampicillin/amoxicillin

 

Tests:

– FBC –> Shows lymphocytosis – with an increase in white cells to between 12-18×109/L,

– Of these, over 50% are lymphocytes and on a blood film at least 10% of these will be atypical

– Heterophile Antibody test –> tests for IgM antibodies to viral antigen in the serum

– Taken in the 2nd week of illness and combined with FBC to confirm diagnosis

– Negative test suggests CMV could be a cause of the infectious mononucleosis

 

Treatment – Supportive with paracetamol and disulfiram mouthwash as it self-resolves after 2-4 weeks

– If inability to swallow, then admit to hospital for IV fluids and give dexamethasone

– Avoid playing contact sports/activities for 8 weeks due to risk of rupturing the spleen

 

Complications EBV increases risk of developing Burkitt’s + Hodgkin’s lymphoma

Also, higher risk of Multiple Sclerosis, Guillain Barre and nasopharyngeal carcinoma

 

  • Varicella Zoster Virus (VZV)

Otherwise known as Human alpha-herpesvirus 3, VZV is a DNA virus that causes an initial infection but then stays dormant in sensory ganglia.

– It usually causes chickenpox in children but then can reactivate from dormancy causing other conditions

 

– Chickenpox

This is a primary infection usually seen in children due to the varicella zoster virus

– It is spread via the airways and the rash develops 4 days post infection

– The most infectious period is 1-2 days before you get the rash and continues till all lesions are dry

 

Symptoms – Prodrome of high temperature

– Pruritic vesicular rash on head and torso before spreading

– Can lead to secondary bacterial infection of lesions (especially with NSAID use)

 

Complications Can lead to pneumonia + encephalitis

Disseminated haemorrhagic chickenpox –> seen in immunocompromised

 

Treatment – Supportive treatment keeping cool + applying calamine lotion

– If immunocompromised or baby with peripartum exposure –> give varicella zoster immunoglobin

– Shingles

A painful rash with blisters that occurs due to reactivation of VZV from sensory ganglia

 

Risk factors – Old age, immunocompromised, having chickenpox at age < 18 months

 

Symptoms – Painful vesicular rash in a strip on the body (following dermatome)

– 2-4 days before, there may be pain or tingling in the area

Treatment – 1st line is oral acyclovir and rash usually heals within 2-4 weeks

– However, patients can develop post-herpetic neuralgia, a neuropathic pain in the dermatome affected by VZV

 

Vaccine – Live-attenuated virus given subcutaneously to patients aged 70-79

– Contraindicated in immunosuppressed patients due to risk of developing chickenpox

 

– Herpes Zoster Opthalmicus

This refers to VZV reactivation from latency within the ophthalmic branch of the trigeminal nerve

– Classically is proceeded by Hutchinson’s sign –> the nasociliary branch of the ophthalmic nerve may be affected first causing a vesicular rash to appear on the side of nose

– This can quickly lead to infection of the eyes so must be managed quickly

 

Symptoms – Vesicle-type rash occurring around or on the eyes with swelling of the eyelid

– Eye pain, redness and sensitivity to light

– Fever and tingling preceding rash

– Can lead to chronic pain (post-herpetic neuralgia) and vision loss

 

Treatment – 1st line Oral acyclovir for 7-10 days –> if severe IV antiviral

– If eye involvement, refer to ophthalmology

 

– Ramsay Hunt syndrome (Herpes Zoster Oticus)

This is VZV reactivation from latency within CNVII, the facial nerve’s geniculate ganglion.

 

  • AIDS

This is a condition caused by Human Immunodeficiency Virus (HIV) which invades CD4 T cells and gives progressive depletion. This leads to Acquired Immunodeficiency Syndrome (AIDS)

– GP120 binds CD4 allowing entry into cell –> virus then replicates inside and destroys cell

– As infection progresses, causes depletion of CD4 decreasing immune function

Transmission: Sexual Transmission + Vertical (mother to baby) + drug usage

 

Symptoms:

i) Seroconversion (3-12 weeks following infection):

– Flu-like symptoms with fatigue, fever, lymphadenopathy, sore throat and arthralgia

– Erythematous popular rash and mouth ulcers

– Persistent generalized lymphadenopathy –> swollen lymph nodes lasting > 3months

 

ii) Chronic infection – This is usually asymptomatic until you get complications of immunosuppression

 

Complications:

i) Pneumocystis Jirovecii –> An AIDS defining opportunistic infection.

– Prophylaxis with co-trimoxazole is recommended for patients with a CD4 count < 200/mm3

 

ii) Cryptococcus Neoformans – commonest systemic fungus in HIV which causes meningitis

 

iii) Oesophageal Candidiasis – This is when the yeast Candida causes inflammation of the oesophagus

– Gives dysphagia and pain when swallowing and can lead to weight loss

– Seen in patients with CD4 count < 100

 

Treatment – 1st line is fluconazole + Itraconazole

iv) Kaposi’s sarcoma – Human herpes virus 8 infection, resulting in cancer

– Classically patients first develop purple skin lesions (patches/ plaques)

– It then spread to the mouth/GI/respiratory tract

– Tumour spreads early and needs treatment with antiretroviral agents

 

DiagnosisIn asymptomatic person, test at 4 weeks after exposure

a) ELISA –> most accurate test which tests for HIV antibody/antigen

b) Rapid-point of care testing – this is an immunoassay key which gives a rapid result from finger prick.

c) Viral load – this is a quantification of HIV RNA –> used to monitor response to ART, not diagnose

d) CD4 count – not diagnostic but uses to monitor immune system function and disease progression.

 

Treatment – Common therapy is to use 2 nucleoside reverse transcriptase inhibitors + 3rd drug

– This is called highly active anti-retroviral therapy (HAART)

 

N.B. If you accidentally are exposed to HIV virus, you can get post-exposure prophylaxis- This maybe because of a needle stick injury or unprotected sexual intercourse

– Treatment involves combination of anti-retrovirals started up to 72 after exposure and taken for 4 weeks

– Then take serological test at 12 to check whether you are infected.

1. National Cancer Institute, AV-8500-3620 (Wikipedia Commons)

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