Viruses Flashcards
What is the route of infection of chicken pox?
A common childhood disease in the UK. The route of infection is via the mucosa of the URT or conjunctivae. The mouth and conjunctivae are often involved.
What is the presentation of chicken pox?
- There is prodrome of fever and lethargy followed by an itchy vesicular rash. Lesions spread from the face and trunk to the limbs.
- The rash starts as macules and papules but forms clear fluid-filled blisters called vesicles which burst and crust over. Often the vesicles contain pus and different stages of the rash are present at once.
What are complications of chicken pox?
- Usually self-limiting so requires supportive care only
- In adults and immunocompromised patients especially, the infection can be very severe
- Pneumonitis is the most severe complication - requires hospital admission
- Other complications include bacterial infection of skin lesions; encephalitis and other neurological problems, hepatitis and myocarditis.
What are common causes for compromised immune system?
- Diabetes
- HIV
- Haematological disorders and malignancies
- Extremes of age i.e. very elderly people and neonates, pregnancy
- Patients with systemic inflammatory conditions such as RA and patients on immunosuppressive meds e.g. chemo
What are risk factors for varicella pneumonitis?
- Smoking
- Pregnancy
- Compromised immune system
- Chronic lung disease
What medications are available for VZV?
- Varicella zoster vaccine available for non-immune patients at risk for severe disease
- Aciclovir is active against VZV. In mild infections supportive care is all that is required.
What infections do HSV, EBV and CMV cause?
- HSV causes oral, ocular and genital ulcers and rarely encephalitis
- EBV causes glandular fever and is associated with certain cancers e.g. Burkitt’s lymphoma
- CMV causes disease in patients who are immunocompromised e.g. retinitis in patients with HIV and tissue rejection in transplant patients
What is shingles?
Shingles vesicles contain VZV which can cause chickenpox if transmitted to a non-immune person. Chicken pox is the primary infection whereas shingles represents reactivation of latent VZV. Following primary infection, VZV lies dormant in single sensory nerves or dorsal root ganglia.
What triggers reactivation of VZV?
Usually triggered by immune compromise and leads to a rash in the area of skin supplied by these nerves (dermatome). One or less commonly multiple dermatomes may be affected (dermatomes do not cross the mid-line of the body). Pain usually preceeds the rash because of reactivation in the nerve. The rash itself is similar to chickenpox.
How do you test for past exposure to VZV in regards to pregnancy?
Test for VZV IgG - a blood sample should be sent urgently. If it is positive then no further action is needed as they have been exposed to it (immune). If negative, a mother is at risk of becoming infected and should be given VZV immunoglobulin to provide her with temporary passive immunity. Women may also be given antiviral medications according to guidelines. VSV vaccination should be considered.
When is VZV the biggest risk in pregnancy?
The risk of severe disease in the mother is higher during the 3rd trimester when they are relatively immunocompromised and more likely to develop pneumonitis. The risk to the foetus is greatest in the first 12 weeks. VZV is one of the TORCH infections.
When is aciclovir given in pregnancy for VZV?
- <20 weeks then give IVIG ASAP within 10 days
- For susceptible women exposed after 20 weeks either VZIG or oral aciclovir at 800mg 4x/day from days 7-14 after exposure. Valaciclovir 100mg 3x/day from days 7-14 after exposure as alternative.
- Oral aciclovir if woman >20 weeks presents within 24hrs of the rash starting
How does the measles virus present?
Measles presents with a prodrome of fever, malaise, conjuncitivitis and cough. Blue-grey spots called Koplik spots appear inside the buccal mucosa but disappear early so may not be picked up by the clinician. Then the rash appears as a morbilliform or maculopapular rash that starts on the face and moves down the body. The rash become confluent i.e. the spots merge into one another.
What are the complications of measles?
- Bacterial pneumonia
- Otitis media
- Acute encephalitis
- Subacute sclerosing pan-encephalitis is a rare chronic degenerative neurological problem that can occur years after primary infection
What is the course of an HSV infection?
Majority of people are asymptomatic, however, primary infection can present as severe gingivostomatitis with systemic symptoms, especially in children. HSV1 usually causes oral or ocular disease and HSV2 cause genital lesions, however both viruses can cause disease in either part of the body. After primary infection, HSV ascends sensory nerves and lies dormant in the dorsal root ganglia. Following a period of latency, HSV has the ability to reactivate and cause recurrent disease. It presents as painful ulcers on the genitalia or mouth.
