Common viral infections

Question 1

Common viral infections

The human herpesviruses

Answer 1

• currently eight known human herpesviruses: herpes simplex virus 1 and 2 (HSV1 and HSV2), varicella zoster virus (VZV), cytomegalovirus (CMV), Epstein–Barr virus (EBV), and human herpesviruses 6, 7 and 8 (HHV 6–8). HHV8 is associated with Kaposi sarcoma in HIV-coinfected individuals
• hallmark of the herpesviruses is that, after primary infection, latency is established and there is long-term persistence of the virus within the host, usually in a dormant state. After certain stimuli, reactivation of infection may occur

Question 2

Common viral infections

Herpes simplex infections

Herpes simplex virus infections

• Most are asymptomatic
• Gingivostomatitis – may necessitate intravenous fluids and aciclovir
• Skin manifestations – mucocutaneous junctions, e.g. lips and damaged skin
• Eczema herpeticum – may result in secondary bacterial infection and septicaemia
• Herpetic whitlows – painful pustules on the fingers
• Eye disease – blepharitis, conjunctivitis, corneal ulceration and scarring
• CNS – aseptic meningitis, encephalitis
• Pneumonia and disseminated infection in the immunocompromised.

Answer 2

• Herpes simplex virus (HSV) usually enters the body through the mucous membranes or skin, and the site of the primary infection may be associated with intense local mucosal damage.
• HSV1 is usually associated with lip and skin lesions, and HSV2 with genital lesions, but both viruses can cause both types of disease

Question 3

Common viral infections

Chickenpox (primary varicella zoster infection

Chickenpox

• Clinical features – fever and itchy, vesicular rash which crops for up to 7 days
• Complications – secondary bacterial infection, encephalitis; disseminated disease in the immunocompromised
• Human varicella zoster immunoglobulin (VZIG) – if immunosuppressed and in contact with chickenpox or if maternal chickenpox shortly before or after delivery
• Treatment is symptomatic; i.v. aciclovir for severe chickenpox or the immunocompromised

Answer 3

Complications that can occur in previously healthy children:

• Secondary bacterial infection with staphylococci, group A streptococcal, or other organisms. May lead to further complications such as toxic shock syndrome or necrotising fasciitis
• Encephalitis. This may be generalised, usually occurring early during the illness. In contrast to the encephalitis caused by HSV, the prognosis is good. Most characteristic is a VZV-associated cerebellitis.
• Purpura fulminans. This is the consequence of vasculitis in the skin and subcutaneous tissues. It is best known in relation to meningococcal disease and can lead to loss of large areas of skin by necrosis

Question 4

Common viral infections

Shingles (herpes zoster)

Answer 4

• Shingles is uncommon in children. It is caused by reactivation of latent varicella-zoster virus (VZV), causing a vesicular eruption in the dermatomal distribution of sensory nerves (shingles)
• Shingles in childhood is more common in those who had primary infection in the first year of life. Recurrent or multidermatomal shingles is strongly associated with underlying immune suppression, e.g. HIV infection
  *

Question 5

Common viral infections

Epstein–Barr virus: infectious mononucleosis (glandular fever)

Answer 5

• Epstein–Barr virus (EBV) major cause of the infectious mononucleosis syndrome, also involved in the pathogenesis of Burkitt lymphoma, lymphoproliferative disease in immunocompromised hosts and nasopharyngeal carcinoma
• Older children, and occasionally young children, may develop a syndrome with:
  
  • fever
    malaise
    tonsillopharyngitis – often severe, limiting oral ingestion of fluids and food; rarely, breathing may be compromised
    lymphadenopathy – prominent cervical lymph nodes, often with diffuse adenopathy.
• Other features include:
  • petechiae on the soft palate
    splenomegaly (50%), hepatomegaly (10%)
    a maculopapular rash (5%)
    jaundice.
• Diagnosis is supported by:
  • atypical lymphocytes (numerous large T cells seen on
    blood film)
• a positive Monospot test (the presence of heterophile antibodies, i.e. antibodies that agglutinate sheep or horse erythrocytes but which are not absorbed by guinea pig kidney extracts – this test is often negative in young children with the disease)
• seroconversion with production of IgM and IgG to Epstein–Barr virus antigens.

Question 6

Common viral infections

Cytomegalovirus

Answer 6

• transmitted via saliva, genital secretions or breast milk, and more rarely via blood products, organ transplants and transplacentally
• causes mild or subclinical infection in normal hosts
• As with EBV, CMV may cause a mononucleosis syndrome
• Patients may have atypical lymphocytes on the blood film but are heterophile antibody-negative. Maternal CMV infection may result in congenital infection
• In the immunocompromised host, CMV can cause retinitis, pneumonitis, bone marrow failure, encephalitis, hepatitis, colitis and oesophagitis. It is a very important pathogen following organ transplantation
• CMV disease may be treated with ganciclovir or foscarnet, but both have serious side-effects.

Question 7

Common viral infections

Human herpesvirus 6 (HHV6) and HHV7

Answer 7

• Human herpesvirus 6 (HHV6) and HHV7 are closely related and have similar presentations, although HHV6 is more prevalent
• children are infected with HHV6 or HHV7 by the age of 2 years, usually from the oral secretions of a family member
• children are infected with HHV6 or HHV7 by the age of 2 years, usually from the oral secretions of a family member
• Exanthem subitum is frequently clinically misdiagnosed as measles or rubella; these infections are rare in the UK and if suspected should be confirmed serologically

Question 8

Common viral infections

Parvovirus B19

(Slapped cheek syndrome)

• Parvovirus B19 causes erythema infectiosum or fifth disease (so-named because it was the fifth disease to be described of a group of illnesses with similar rashes), also called slapped-cheek syndrome.
• Infections can occur at any time of the year, although outbreaks are most common during the spring months.
• Transmission is via respiratory secretions from viraemic patients, by vertical transmission from mother to fetus and by transfusion of contaminated blood products.
• Parvovirus B19 infects the erythroblastoid red cell precursors in the bone marrow.

Answer 8

Causes a range of clinical syndromes:

• Asymptomatic infection – common; about 5–10% of preschool children and 65% of adults have antibodies
• Erythema infectiosum – the most common illness, with a viraemic phase of fever, malaise, headache and myalgia followed by a characteristic rash a week later on the face (’slapped-cheek’), progressing to a maculopapular, ‘lace’-like rash on the trunk and limbs
• Aplastic crisis – the most serious consequence of parvovirus infection; it occurs in children with chronic haemolytic anaemias, where there is an increased rate of red cell turnover
• Fetal disease – transmission of maternal parvovirus infection may lead to fetal hydrops and death due to severe anaemia, although the majority of infected fetuses will recover

Question 9

Common viral infections

Enteroviruses

Enterovirus infection:

• Mostly asymptomatic or self-limiting illness with rash, which may be purpuric
• Can cause hand, foot and mouth disease, herpangina, or meningitis/encephalitis.

Answer 9

• Human enteroviruses, of which there are many (including the coxsackie viruses, echoviruses and polioviruses), are a common cause of childhood infection
• Transmission by the faecal–oral route, replicates in pharynx and gut then virus spreads to infect other organs
• better to treat a number of enteroviral infections than to send home a child with meningococcal disease, only to have them return moribund 12 h later.