Day: April 9, 2012

How Common Is Human Metapneumovirus?

Patient Presentation
Patient Presentation
A 15-year-old male came to the emergency room with cough, runny nose and fever to 101.5° F for 2 days. The cough was increasing in intensity overall and occurred day and night. There was no paroxysmal quality and the patient said he felt breathless. The past medical history was positive for mild intermittent asthma with the last episode occurring more than 5 years ago. He denied chest pain, myalgia, arthralgia, sore throat, emesis, nausea or diarrhea.

The pertinent physical exam showed a tired appearing male whose oxygen saturation was 93%, respiratory rate of 40, with a normal pulse, blood pressure and growth parameters. He had very mild intercostal retractions, but no tracheal tugging or nasal flaring. He had no cyanosis or stridor. HEENT showed mild clear rhinorrhea. Lungs revealed very mild intermittent wheezes at the bases. The rest of the examination was normal. The radiologic evaluation demonstrated some mild perihilar streaking without focal abnormalities consistent with viral pneumonia. The diagnosis of viral pneumonia was made. The patient was given an albuterol nebulizer treatment and had some moderate improvement. He was discharged home with followup in 2 days with his regular physician. At followup he reported some moderate improvement with albuterol treatments and his fever had subsided 1 day previously. He was not tachypneic and had no signs of respiratory distress. The laboratory evaluation of a nasal wash specimen done in the emergency room was positive for human metapneumovirus.

Discussion
Acute respiratory infections particularly clinical pneumonia are one of the most common causes of death world-wide. Clinical pneumonia in children less than 5 years old in developing countries is approximately 0.29 episodes per child-year or about 151.8 million cases per year of which 8.7% require hospitalization. An additional 4 million children are hospitalized in developed countries per year. There are great differences across the world with the distribution of pneumonia cases. The 5 countries with the highest incidence of clinical pneumonia are India, China, Pakistan, Bangladesh and Nigeria. Even within these countries there are differences, for example rural areas often have higher incidences. Estimates of pneumonia mortality in children less than 5 years of age is about 2 million per year. This is probably an underestimate especially in the neonatal age group. Again there are differences in the distribution of the deaths ranging from 45% in Africa to 2-3% in Europe and the Americas. About 2/3rds of deaths occur in 10 countries: India, Nigeria, Democratic Republic of the Congo, Ethiopia, Pakistan, Afghanistan, China, Bangladesh, Angola and Niger.

Definite risk factors affecting the incidence of childhood pneumonia include low birth weight, malnutrition, non-exclusive breastfeeding during the first 4 months of life, lack of measles vaccination in first 12 months of life, crowding and indoor air pollution. Other likely risk factors include maternal caregiving experience, parental smoking, concomitant diseases and zinc deficiency.

Common bacterial organisms causing pneumonia worldwide include Streptococcus pneumonia (leading bacterial cause when isolated), H. influenza type b and non-typeable, Staphlococcus aureus, Klebsiella pneumonia, Mycobacterium tuberculosis, and non-typhoid Salmonella. Other important organisms causing pneumonia including Mycoplasma pneumoniae, Chlamydia species, Pseudomonas, Escherichia coli, and Pneumocystis. Common viral causes of pneumonia include Respiratory Syncytial virus, Influenza and B, Parainfluenza, Human metapneumovirus and Adenovirus. Measles and varicella are two other important causes. RSV is the most common viral cause when isolated in many studies.

There can be difficulties in detecting respiratory viruses including not actually testing for a particular organism or differences in detection methods. One study in Finland found ~15% (5% for each group) of rapid virus detection specimens had adenovirus, human metapneumovirus and human bocavirus (a Parvoviridae virus causing respiratory infections identified in 2005). Co-infection rates between the viruses ranged from 1% (hMPV and Adenovirus) to 12% (hMPV and Human Bocavirus). hMPV and RSV was 4%. In another study in China found co-infection rate of hMPV and RSV of 25%.

Learning Point
Human metapneumovirus (hMPV) is a single-stranded RNA virus in the Paramyxoviridae family that is closely related to avian metapneumovirus. It was identified in 2001 in the Netherlands. It can cause illnesses that range from asymptomatic to severe respiratory distress and possibly death. Young children under age 2 are particularly susceptible. Twenty-five percent of children 6-12 months were seropositive for past infection and this increased to 100% by age 5. hMPV can occur in all ages. It occurs in all areas of the world and is seasonal in nature.

Questions for Further Discussion
1. What are indications for hospitalization for pneumonia?
2. What treatment is available for patient hospitalized with pneumonia?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for this topic: Pneumonia</a

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

Arnold JC, Singh KK, Spector SA, Sawyer MH. Undiagnosed Respiratory Viruses in Children. Pediatrics. 2008;121;e631.

Rudan I, Boschi-Pinto C, Biloglav Z, Mulholland K, Campbell H. Epidemiology and etiology childhood pneumonia. Bulletin of the World Health Organization. 2008;321-416.

Domachowske J, and Steele RW. Pediatric Human Metapneumovirus. Medscape. Available from the Internet at http://emedicine.medscape.com/article/972492-overview (rev. 10/24/11, cited 2/19/12).

Zhao X, Chen X, Zhang Z. Outbreak of Human Metapneumovirus Infection in Children in Chongqing, China. Pediatrics. 2008;s135.

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients’ is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    4. Patient management plans are developed and carried out.
    5. Patients and their families are counseled and educated.
    7. All medical and invasive procedures considered essential for the area of practice are competently performed.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Practice Based Learning and Improvement
    13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.

    Author

    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa Children’s Hospital