Lassa fever

Viral Hemorrhagic Fever Consortium: case definition for suspected cases of Lassa fever[12]Shaffer JG, Grant DS, Schieffelin JS, et al. Lassa fever in post-conflict Sierra Leone. PLoS Negl Trop Dis. 2014;8:e2748. http://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0002748 http://www.ncbi.nlm.nih.gov/pubmed/24651047?tool=bestpractice.com

In those epidemiologically exposed:

• Fever >38°C for <3 weeks, plus

• Absence of signs of local inflammation, and

• Two major signs, or one major and two minor signs:

  • Major sign:

    • Bleeding

    • Swollen neck or face

    • Conjunctivitis or subconjunctival haemorrhage

    • Spontaneous abortion

    • Petechial or haemorrhagic rash

    • New onset tinnitus or altered hearing

    • Persistent hypotension

    • Absence of clinical response after 48 hours to anti-malarial and/or broad-spectrum antibiotic therapy.

  • Minor sign:

    • Headache

    • Sore throat

    • Vomiting

    • Diffuse abdominal pain/tenderness

    • Chest/retrosternal pain

    • Cough

    • Diarrhoea

    • Generalised myalgia or arthralgia

    • Profuse weakness.

World Health Organization (WHO): recommended case definition for Lassa fever[37]World Health Organization. WHO recommended surveillance standards. Second edition. Feb 1999 [internet publication]. https://www.who.int/publications/i/item/who-recommended-surveillance-standards

Clinical description:

An illness of gradual onset with one or more of the following:

• Malaise

• Fever

• Headache

• Sore throat

• Cough

• Nausea

• Vomiting

• Diarrhoea

• Myalgia

• Chest pain

• Hearing loss

and

• A history of contact with excreta of rodents, or contact with a probable or confirmed case of Lassa fever.

Laboratory criteria for diagnosis:

• Isolation of virus from blood, urine, or throat washings, or

• Positive IgM serology or seroconversion (IgG antibody) in paired serum specimens, or

• Identification of Lassa virus antigen in autopsy tissues by immunohistochemistry or in serum by ELISA

• Positive PCR (in serum or autopsy tissues).

Case classification:

• Suspected: case compatible with the clinical description

• Probable: suspected case that is epidemiologically linked to a confirmed case

• Confirmed: suspected case that is laboratory confirmed

• Contact: person having close personal contact with the patient (living with, caring for) or a person testing the laboratory specimens of a patient in the 3 weeks after the onset of the illness.