Avian Influenza Clinical Picture, Risk profile & Treatment Jantjie Taljaard Adult ID Unit Tygerberg Academic Hospital University of Stellenbosch jjt@sun.ac.za 083 419 1452
CLINICAL PICTURE The clinical spectrum of influenza A (H5N1) in humans is based on descriptions of hospitalised patients The frequency of milder illnesses, subclinical infections and atypical presentations have not been determined, but case reports indicate that each occurs
N Engl J Med. 2004 March 18; 350(12):1179-88
CLINICAL PICTURE Incubation period For classic human influenza viruses 2 to 3 days (range 1 7 days) For human influenza A (H5N1) Currently uncertain but may be longer The case-to-case intervals in household clusters have generally been 2-5 days.
CLINICAL PICTURE Symptoms High fever (> 38 o C) and an influenza like illness Lower respiratory tract symptoms like cough and shortness of breath are the usual initial presenting features Muscle pains, Malaise, Sore throat Watery diarrhoea without blood or inflammatory changes Although uncommon, may be more common than in classic influenza A and may precede respiratory symptoms with up to one week Other less common initial symptoms include: Vomiting, abdominal pain, pleuritic pain, bleeding from nose and gums and encephalopathy
CLINICAL PICTURE Physical examination Most patients are previously healthy young children and adults. May be tachypnoeic May have inspiratory crackles present Sputum production is variable (may even be bloody)
CLINICAL PICTURE Chest X-ray changes Almost all patients have clinical apparent pneumonia and CXR changes include: Diffuse, multifocal or patchy infiltrates Interstitial infiltrates Segmental or lobular consolidation with air bronchograms Radiographic changes are present on average 7 days after the onset of symptoms
N Engl J Med. 2004 March 18;350(12):1179-88
N Engl J Med. 2005 Jan 27;352(4):333-40
CLINICAL PICTURE Common laboratory findings Lymphopenia (<1 x 109/litre) and Thrombocytopenia at time of admission may be poor prognostic signs Moderately raised aminotransferase levels may also occur
CLINICAL PICTURE Clinical course Rapidly progression to respiratory distress (ARDS) and subsequent respiratory failure usually within 1 week of the onset of symptoms Multiorgan failure are common including: renal failure cardiac compromise (dilatation and/or supraventricular tachyarrhythmias)
CLINICAL PICTURE Mortality On average 9-10 days after onset of symptoms Most patients die due to respiratory failure High mortality rate in hospitalised patients (± 50%) despite adequate ventilation Mortality rate in those younger than 15 years in Thailand was 89%!
CASE DETECTION Early recognition of cases is confounded by: - non-specificity of the initial symptoms - high background rates of acute respiratory illnesses from other causes Detailed contact and travel histories and knowledge of viral activity in poultry are therefore essential!
Scenario 1: HPAI viruses have NOT been identified as a cause of illness in human or animal populations in South Africa Symptomatic: - Fever of 38oC and one or more lower respiratory tract symptoms: Cough, shortness of breath, difficulty in breathing and
During the 7 days before the onset of symptoms one or more of the following: - Close contact with an ill traveler from an area with Influenza A (H5N1) activity - A history of travel to a country or area with reported Influenza A (H5N1) activity in the animal populations - Living in an area in which there are rumors of deaths of domestic fowl and
High risk exposure/contact with one or more of the following: - contact (within 1 meter) with live or dead domestic fowl or wild birds in any setting - exposure to settings in which domestic fowl had been confined in the previous 6 weeks - contact (within touching or speaking distance) with a confirmed human case of Influenza A (H5N1) infection - contact (within touching or speaking distance) with a person with an unexplained acute respiratory illness that later resulted in death - occupational exposure
Scenario 2: HPAI viruses have been identified as a cause of illness in human or animal populations in South Africa Symptomatic: - Fever of 38oC and one or more lower respiratory tract symptoms: Cough, shortness of breath, difficulty in breathing and
High risk exposure/contact during the 7 days before the onset of symptoms with one or more of the following: - contact (within 1 meter) with live or dead domestic fowl or wild birds in any setting - exposure to settings in which domestic fowl had been confined in the previous 6 weeks - contact (within touching or speaking distance) with a confirmed human case of Influenza A (H5N1) infection - contact (within touching or speaking distance) with a person with an unexplained acute respiratory illness that later resulted in death - occupational exposure
CASE MANAGEMENT 1. Isolate all suspected/proven cases for: clinical monitoring diagnostic testing antiviral treatment (if available!) 2. Take respiratory and blood specimens for laboratory testing for influenza and other infections as clinically indicated 3. Treat with a neuraminidase inhibitor such as oseltamivir 75 mg orally, twice daily for 5 days as early in the clinical course as possible. Higher doses for longer periods may be needed for more severe infections.
Case management Hospitalise patients (if clinically indicated) Supportive care is the foundation of management Monitor oxygen saturation and treat desaturation with supplemental oxygen as required Most hospitalised patients required ventilation and ICU admission (for multiorgan failure/shock) within 48hrs after admission
Case management Hospitalise patients Nebulizers and high-air-flow oxygen masks have been implicated in nosocomial spread of SARS use only if clinically justified and apply them under strict airborne transmission precautions Take respiratory and blood specimens serially to check for possible bacterial co-infection consider empirical broad spectrum IV antibiotic therapy to prevent secondary bacterial infections
Case management Hospitalisation not required Educate patient and family on personal hygiene and infection control measures Instruct the patient to seek prompt medical care if the condition worsens Follow up by home visits or telephone contact (as resources permit)
Case management Discharge policy Adults: Studies are required to provide better understanding of viral excretion patterns in humans infected with the influenza A(H5N1) Until further evidence is available: WHO recommends that infection control precautions for adult patients remain in place for 7 days after resolution of fever.
Case management Children: Discharge policy Previous human influenza studies have indicated that children younger than 12 years can shed virus for 21 days after onset of illness. Therefore, infection control measures for children should ideally remain in place for this period. Where this is not feasible (because of a lack of local resources) Educate family on personal hygiene and infection control measures Children should not attend school during this period.
References 1. www.who.int/wer/en 2. www.cdc.gov 3. BMJ - Vol 331; 5 November 2005; Douglas Fleming, Clinical Review: Influenza pandemics and avian flu 4. The Lancet Infectious Diseases - Vol 5; November 2005; Leonard A Mermel, Reflexion and Reaction: Pandemic avian influenza 5. NEJM - Vol 353; 29 September 2005; The Writing Committee of the WHO Consultation on Human Influenza A/H5, Current concepts: Avian Influenza A (H5N1) Infection in Humans
Thank you