# Adenovirus and Parvovirus B19

> Adenovirus and parvovirus B19 for NEET-PG Microbiology, covering conjunctivitis, haemorrhagic cystitis, fifth disease, aplastic crisis and hydrops fetalis.

- Canonical URL: https://prepelephant.com/topics/neet-pg/microbiology/adenovirus-and-parvovirus-b19
- Exam / course: NEET-PG · Subject: Microbiology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-15
- Last updated: 2026-10-15
- Reference basis: Ananthanarayan and Paniker's Textbook of Microbiology; Jawetz, Melnick and Adelberg's Medical Microbiology; Harrison's Principles of Internal Medicine
- How to cite: "Adenovirus and Parvovirus B19", PrepElephant, https://prepelephant.com/topics/neet-pg/microbiology/adenovirus-and-parvovirus-b19

## Direct answer

Adenoviruses are non-enveloped, double-stranded DNA viruses that cause conjunctivitis, pharyngitis and haemorrhagic cystitis. Parvovirus B19 is a non-enveloped, single-stranded DNA virus that infects erythroid progenitor cells, causing fifth disease and transient aplastic crisis. Each virus produces a classic syndrome that follows directly from the tissue it targets.

## What you must remember

- **Adenovirus genome:** Linear double-stranded DNA in an icosahedral capsid, with more than 50 serotypes grouped into species A to G.
- **Pharyngoconjunctival fever:** Serotypes 3 and 7 cause fever, pharyngitis and conjunctivitis, often spreading in school outbreaks.
- **Epidemic keratoconjunctivitis:** Serotypes 8, 19 and 37 cause severe conjunctivitis, sometimes with corneal subepithelial infiltrates.
- **Haemorrhagic cystitis:** Serotypes 11 and 34 classically cause it, mainly in haematopoietic stem cell transplant recipients.
- **Parvovirus B19 receptor:** The P antigen, a globoside on erythroid progenitors, is the receptor that determines its tropism.
- **Fifth disease:** Erythema infectiosum in children, with a slapped-cheek facial rash followed by a lacy reticular rash.
- **Aplastic crisis:** Transient cessation of red cell production in haemolytic anaemias such as sickle cell disease and thalassaemia.
- **Hydrops fetalis:** Maternal infection can cause fetal anaemia and hydrops, with the greatest risk when infection occurs early in pregnancy.

## A diagnostic pathway for fever, rash or anaemia

Adenovirus and parvovirus B19 can overlap in presentation, so the host and the organ involved guide the test. Work through these steps in order when a case is presented.

1. **Ask about the host:** Disseminated adenovirus concerns transplant recipients, while a pregnant woman or a child with chronic haemolysis raises concern for parvovirus B19.
2. **Look at the organ involved:** Eye or bladder involvement points to adenovirus, whereas a slapped-cheek rash or a sudden fall in haemoglobin points to parvovirus B19.
3. **Send the right sample:** Conjunctival swabs or urine are suited to adenovirus PCR, and serum is used for B19 IgM, with PCR reserved for immunocompromised patients who may not mount an IgM response.
4. **Interpret antibodies carefully:** B19 IgM signals recent infection, while IgG indicates past infection and immunity.
5. **Treat the cause where possible:** Immune globulin is used for chronic parvovirus B19 infection in immunocompromised patients, and cidofovir has been used for severe disseminated adenovirus.

## Where the exam tries to catch you

Questions on these two viruses usually hinge on the target cell and the classic syndrome it produces.

- **Trap:** Expecting the rash to be the main threat of parvovirus B19. **Correct:** The real danger is suppression of red cell production, which causes aplastic crisis in haemolytic patients and fetal anaemia in pregnancy.
- **Trap:** Blaming adenovirus for every case of haemorrhagic cystitis after transplant. **Correct:** BK polyomavirus is the other major cause after stem cell transplant, and in renal transplant recipients it causes nephropathy rather than typical haemorrhagic cystitis.
- **Trap:** Confusing fifth disease with roseola. **Correct:** Fifth disease is caused by parvovirus B19, while roseola is caused by human herpesvirus 6.

## Frequently asked questions

### Which adenovirus serotypes cause epidemic keratoconjunctivitis?
Adenovirus serotypes 8, 19 and 37 are the classic causes of epidemic keratoconjunctivitis. The infection spreads readily through contaminated instruments and hands, and corneal subepithelial infiltrates may persist for weeks.

### Why does parvovirus B19 cause aplastic crisis?
Parvovirus B19 suppresses erythroid progenitor cells, which halts red cell production for a short period. In patients with haemolytic anaemia such as sickle cell disease, the shortened red cell survival turns this pause into a sharp fall in haemoglobin.

### What is erythema infectiosum?
Erythema infectiosum is the medical name for fifth disease, a childhood illness caused by parvovirus B19. It produces a slapped-cheek facial rash, followed by a lacy reticular rash on the limbs and trunk.

### Why is parvovirus B19 dangerous in pregnancy?
Parvovirus B19 crosses the placenta and suppresses fetal red cell production, which can lead to fetal anaemia and hydrops fetalis. Severe cases may need intrauterine transfusion, and the risk of fetal loss is highest when maternal infection occurs early in pregnancy.

### Which adenovirus types cause haemorrhagic cystitis?
Adenovirus serotypes 11 and 34 are the classic causes of haemorrhagic cystitis, mainly in haematopoietic stem cell transplant recipients. BK polyomavirus is the other major cause after stem cell transplant, so urine PCR for both viruses is sent.