Antigenic characterization of influenza and SARS-CoV-2 viruses
Influenza - University of Colorado Denver · Learning Objectives • Understand the mechanisms by...
Transcript of Influenza - University of Colorado Denver · Learning Objectives • Understand the mechanisms by...
Influenza
Global Health & Disasters Course October 19, 2016
Wayne Sullender, MDCenter for Global HealthDepartment of Pediatrics
University of Colorado Anschutz Medical [email protected]
Learning Objectives• Understand the mechanisms by which antigenic shift and antigenic drift occur in influenza viruses and the epidemiologic implications of these changes.
• Recognize the burden of disease due to influenza in developing countries and among displaced populations.
• Describe the options for the prevention of influenza virus infections and planning for influenza pandemics.
Pneumonia killed 965,000 in 2013: more than AIDS, malaria, and measles combined.
Liu 2014 Lancet, Global, regional, and national causes of child mortality in 2000‐13
Pneumonia2013
Global burden of disease due to influenza in children < 5 years is substantial
90 million cases of influenza20 million influenza acute lower respiratory infections (13% of all ALRI)1 million influenza-associated severe ALRI (7% of cases of all severe ALRI)28,000–111,500 deaths in children, influenza-associated ALRI 99% of these deaths in developing countries.
Estimates for 2008, Lancet 2011 (0140-6736), 378 (9807), p 1917
Influenza Virion Segmented RNA genome
Hemagglutinin (HA):
Cell attachment, membrane fusion
Neutralizing antibodies block attachment and fusion
Neuraminidase (NA):
Cleaves sialic acid, prevents virionclumping
Antibodies block virion release
Influenza A: H1N1, H3N2, etc
Katz, CDC www.preventinfluenza.org/NIVS_2011/2-katz_vaccine_technologieswww.cdc.gov/flu/images
quasispecies
Antigenic driftIndividual genetic changes, RNA polymerase lacks proof-reading/editingError prone replication
RNA viruses: swarm of non-identical but closely related genomes or quasispeciesSelective pressure: mutants with growth advantages become predominant. [Curr Top Microbiol Immunol. 1992;176:1-20]
Influenza Antigenic Changes
Influenza Reassortment: Reassortment of genomic segments creates hybrid virus: antigenic shift, pandemics
Antigenic Drift:Minor antigenic changes in HA and NACauses local outbreaks, requires vaccine changes.
Murray Medical Microbiology
2013: Most Recent H7N9 Flu Deadlier Than H1N1
H7N9 emerged by reassortment (antigenic shift). May have occurred in habitats shared by wild and domestic birds.
Most of those infected had contact with infected poultry or contaminated environments.
665 cases and 229 deaths reported globally from March 2013 through May 9, 2015, most from mainland China
Alexandra Sifferlin June 24,2013 healthland.time.com/2013/06/24/most‐recent‐h7n9‐flu‐deadlier‐than‐h1n1http://wwwnc.cdc.gov/travel/notices/watch/avian‐flu‐h7n9‐china
UNHCR: highest levels of displacement on record, ½ are
children.
http://www.unhcr.org/images/infographics/FiguresAtAGlance‐16JUN2016.png downloaded 10.5.2016
34,000 people are forcibly displaced every day
Communicable diseases, alone or with malnutrition, account for most deaths in complex emergencies
Lancet 2004, 364:1974‐1983
Preventive measure Impact on spread of
Site planning Diarrhea, acute respiratory infection (ARI)Clean water Diarrhea, typhoid, guinea wormGood sanitation Diarrhea, vector‐borne diseases, scabiesAdequate nutrition Tuberculosis, measles, ARI
VaccinationMeasles, meningitis, yellow fever, Japanese encephalitis, diphtheria, influenza
Vector controlMalaria, leishmaniasis, plague, dengue, Japanese encephalitis, yellow fever, etc
Personal protection Malaria, leishmaniasis (insecticide‐treated nets)Personal hygiene Louse‐borne diseases (also ARI)Health education STDs, HIV/AIDS, Diarrhoea
Case‐managementARI, diarrhea, tuberculosis, meningitis, vector borne diseases
Respiratory viral infections in two long‐term refugee camps in Kenya, 2007‐2010: high rates of illness
among children
10 ‐90% specimens (+) for at least one virus among children < 5 yrs with severe ARI BMC Infect Dis. 2012 Jan 17;12:7
Influenza in Refugees on the Thailand–Myanmar Border, May–October 2009
Monthly Incidence (per 1,000 population) (A) URI and (B) ALRI
URI and ALRI common Influenza in 20% influenza‐
like illnesses, 23% of pneumonias
Emerg Infect Dis. 2010 Sep;16(9):1366‐72
Burden of acute respiratory infections in crisis‐affected populations
• Systematic review on the burden of ARI.• ARI always within the top four causes of hospitalization.• ARI the first or second most frequent cause of outpatient consultation.
• ARI among the top three causes of death in all but one study, irrespective of age group.
• Very high excess morbidity and mortality (20‐35% mortality) due to ARI
Confl Health. 2010 Feb 11;4:3. doi: 10.1186/1752‐1505‐4‐3
Risk factors morbidity and mortality from pandemic influenza in refugee/displaced populations
• overcrowding• poor access to basic health‐care services• malnutrition• communicable diseases• logistic challenges, remote locations or ongoing conflict • lack of adequate surveillance to detect cases • poor links to national disease surveillance systems• possible exclusion from national influenza preparedness activities
• lack of staff to investigate outbreaks and manage ill persons.
Pandemic influenza preparedness and mitigation in refugee and displaced populations WHO 2008
Influenza Planning
• Improved influenza surveillance with global coordination
• International/national/regional/local planning and development of surge capacity
• Plans for vaccine development, production, and administration
• Antiviral susceptibility testing and consideration of antiviral stockpiling/dispensation
Pandemic influenza preparedness and mitigation in refugee and displaced populations WHO 2008
WHO provides surveillance data % samples (+) and influenza type 30Sept, 2016
WHO 5Oct2016 http://www.who.int/influenza/surveillance_monitoring/updates/2016_10_03_influenza_update_273.jpg?ua=1
Shading of countries shows % (+) for influenzaPie charts give virus type
WHO Global Early Warning and Response System (EWARS)
• Brings together expertise in disease outbreaks and humanitarian emergencies to strengthen early warning, alert and response in emergency settings
• technical guidance, training and field‐based tools• EWARS in a box: kit of ruggedized, field‐ready equipment needed to establish and manage surveillance and response activities in field settings without reliable internet or electricity (mobile phones, laptops, solar generators).
www.who.int/features/2016/disease‐early‐warning‐response/en/
Build capacity to cope with a pandemic
• Implement public health measures• Implement communication plans• minimize shortages of essential services such as health care (including for usual burden of disease), access to food, safe water, sanitation, power, communications and security/protection;
• minimize social disruption;• prioritize vulnerable countries • strengthen partnerships with governments to ensure the coordination of activities
Pandemic influenza preparedness and mitigation in refugee and displaced populations WHO 2008
Pandemic response lessons from influenza H1N1 2009 in Asia
• “Despite warm words and pledges, efforts to engage the international community to
ensure equitable sharing of limited resources such as antivirals and vaccines fell short and stockpiles in the main
remained in the rich world.”
Respirology. 2011 Aug;16(6):876‐82
Public Health Measures
Social distancingRespiratory etiquette
Cover coughs and sneezesDo not spit in publicIf using masks, dispose of them or wash them Wash hands Wash hands with soap and clean water carefully and often (and clean surfaces).
Pandemic influenza preparedness and mitigation in refugee and displaced populations WHO 2008
Family/Household Level: measures to mitigate pandemic influenza in low‐resource settings
Prevention• Keep your distance. • Wash your hands, cover your coughs and sneezes. • Isolate your ill
Care • Fluids, nutrition • Fever • Rest • Medications, care seeking
Influenza Other Respir Viruses. 2013 Nov;7(6):909‐13
Community/District Level: measures to mitigate pandemic influenza in low‐resource settings
Prevention• Educate on prevention. • Limit public crowding, gathering, mixing, and contacts
Care • Educate on home care, assist the neediest (including care, food, and water). • Community case management
Influenza Other Respir Viruses. 2013 Nov;7(6):909‐13
Estimated number of persons affected by pandemic influenza in a population of 10,000 in
a crowded, low‐resource setting
Pandemic influenza preparedness and mitigation in refugee and displaced populations WHO 2008
Description rates # persons/day Ill influenza 15-60% up to 100 outpatients 30–50%* up to 50
inpatients Up to 10% * up to 10
Deaths 4% or more * up to 4 or more *of those ill
Hospital Surge Planning
• Screening, surveillance, and tracking of exposed individuals
• Controlled access to facility• Prevention strategies (next slide)• Disease specific admission criteria• Enable continuity of clinical operations• Sustained increase in patients (staff/space)• Additional triage areas• Increased ventilator/ICU needs and support
Pediatric Education in Disasters Manual, Influenza, Nyquist and Berman
Prevention strategies in hospital surge planning
• Isolation and cohorting• Personal protective equipment (PPE: masks, gloves, gowns)
• Vaccination• Antiviral prophylaxis• Environmental controls (separate areas ill/non‐ill patients)
• Visitation and ill staff policies
Pediatric Education in Disasters Manual, Influenza, Nyquist and Berman
Prioritization for vaccine and antivirals
Pandemic influenza preparedness and mitigation in refugee and displaced populations WHO 2008Pediatric Education in Disasters Manual, Influenza, Nyquist and BermanCDC 4Nov2013: http://www.cdc.gov/flu/about/disease/index.htm
Group Rationale
Health‐care workers
HCWs are the highest risk group for infection(also 1st responders: EMTs, police, fire)HCWs may transmit illness to vulnerable patients.
Essential staff Maintain essential services in health facilitiesHigh risk conditions
Risk of severe disease: pregnant women, young, elderly, underlying medical conditions
Influenza ManagementSupportive care
Antivirals: Neuraminidase inhibitors (oseltamivir and zanamivir) for prophylaxis and treatment.Uncertain availability and efficacy in low resource settings.
“Efforts centred on … maintaining and increasing vaccine production, and ensuring access to pharmaceuticals –responses that remain unattainable for many low‐ and middle‐income countries... reflects a particular view of biomedicine that pays inadequate attention to the weak capacity of many health systems.” Glob Public Health. 2012;7 Suppl 2:S111‐26
O2 delivery in 12 African countries: 44% with uninterrupted access to an oxygen source J Infect Dev Ctries. 2010 Aug 4;4(7):419‐24
Current influenza vaccinesSafe Effectiveness is variable and depends on:
– antigenic match and immunogenicity– host factors such as age and immune status
May require annual reformulation due to antigenic changes.
Egg-based technologies limit rapid response and surge capacity for pandemics.
Katz, CDC http://www.preventinfluenza.org/NIVS_2011/2‐katz_vaccine_technologies
Influenza Virus Vaccine for the 2016‐2017 Season, northern hemisphere
• Both inactivated and live attenuated vaccines (only inactivated recommended in USA 2016)
Trivalent:• A/California/7/2009 (H1N1)pdm09‐like virus;• A/Hong Kong/4801/2014 (H3N2)‐like virus;• B/Brisbane/60/2008 ‐like virus (Yamagata lineage).
Quadrivalent influenza vaccines add the following additional B strain to the above trivalent vaccine:• a B/Phuket/3073/2013 ‐like virus (Victoria lineage)www.who.int/influenza/vaccines/virus/recommendations/2016_17_north/en/
Summary• Influenza viruses change constantly on the basis of antigenic drift and shift, requiring reformulation of vaccines and leading to pandemics.
• Influenza virus infections in resource limited settings, including among refugees/displaced persons, cause significant disease in children and adults.
• Control measures include universal hygiene behaviors and social distancing.
• Influenza vaccines and antivirals may be employed if available.