The 2009 Influenza Pandemic Influenza A virus, subtype H1N1

“pandemic” novel strain, the majority of the population has not been exposed to it before (no immunity) flu pandemic highly contagious can infect cells deep in the lungs old flu vaccines are not effective

Flu vs. cold there is no “stomach flu” – if it lasts 24 h and makes you vomit and have diarrhea it’s viral gastroenteritis!

both are caused by viruses and antibiotics, herbal remedies and homeopathic medicines are useless... Cold usually comes on gradually — over the course of a day or two leaves you feeling tired, sneezing, coughing and with a runny nose fever is rare and not very high usually last three to four days, but can hang around for 10 days to two weeks

Flu comes on suddenly feel weak and tired and you could run a fever as high as 40 C muscles and joints will probably ache, you will feel chilled and could have a severe headache and sore throat fever may last three to five days, but you could feel weak and tired for two to three weeks

Signs & symptomsColdFlu Fever Occasional Often above 38.5 C for 2-4 days Headache Frequent, but not severeProminent and often severe Aches/pains SlightOften severe Fatigue/weakness MildCan last 2-3 weeks Extreme exhaustion NeverEarly and prominent Stuffy nose CommonOccasional Sore throat CommonOccasional Cough HackingCan be severe Chest discomfort Mild to moderateCommon, can become severe Onset Gradual (develops over a day or two) Sudden (within a few hours) Cause 200 strains of cold virus3 strains of influenza virus

The Flu

Influenza is mainly a disease of water fowl H1-16\N1-9

Influenza Types Influenza TypesHosts Type AHumans, birds, pigs and horses Type BHumans only Type CHumans only

Influenza Viral Structure an enveloped RNA virus has Hemagluttinin and Neuraminidase glycoproteins on its surface RNPs: ribonucleoproteins, transcribe viral RNA into cellular RNA

Life Cycle influenza attaches itself to cell’s surface using hemagluttinin (H) it is brought into the cells entire and disassembles in it once the virus has made copies of itself it uses nueraminidase (N) to leave the cell

Epidemiology (study of health and illness at the population level) Incubation period 1-4 days Virus first detected just before onset of illness. Virus usually not detected after days. More prolonged shedding in children, and immunosuppressed hosts

...a sneeze

Spread direct transmission (infected person sneezes mucus into the eyes, nose or mouth of another person) through people inhaling the aerozolized droplets produced by infected people coughing, sneezing and spitting hand-to-mouth transmission from either contaminated surfaces or direct personal contact, such as a hand-shake (doorknobs, light switches, bank notes…)

Attack rates: 10-20% general population, selected populations % Typical Season: 200,000 hospitalizations and 36,000 deaths

How Does Influenza Change? Particular characteristic that enables influenza A viruses to cause annual epidemics, even pandemics Type A viruses undergo frequent changes in their surface antigens or proteins Minor changes - antigenic drift Major changes - antigenic shift

Antigenic Drift Occurs among influenza A viruses resulting in emergence of new variants of prevailing strains every year New variants result in seasonal flu each winter Some years are worse than others – partly related to degree of ‘drift’

Antigenic Shift Occurs in two ways: Sudden ‘adaptive’ change during replication of a normal virus OR From an exchange of genes between human strain of an influenza A virus and an animal strain (e.g. avian flu) BIG change, can cause pandemics

PANDEMICS OF INFLUENZA 20 H7 H5 H9 * Recorded new avian influenzas H1N1 H2N Russian influenza H2N Asian influenza H2N2 H3N Hong Kong influenza H3N2 H3N Old Hong Kong influenza H3N Spanish influenza H1N Pandemic influenza H1N1 Recorded human pandemic influenza (early sub-types inferred) Reproduced and adapted (2009) with permission of Dr Masato Tashiro, Director, Center for Influenza Virus Research, National Institute of Infectious Diseases (NIID), Japan. Animated slide: Press space bar H1N1 Pandemic H1N1

GENETIC ORIGINS OF THE PANDEMIC (H1N1) 2009 VIRUS: VIRAL REASSORTMENT 21 PB2 PB1 PA HA NP NA MP NS PB2 PB1 PA HA NP NA MP NS PB2 PB1 PA HA NP NA MP NS Classical swine, N. American lineage Avian, N. American lineage Human seasonal H3N2 Eurasian swine lineage Eurasian swine H1N1 N. American H1N1 (swine/avian/human) Pandemic (H1N1) 2009, combining swine, avian and human viral components

H1N1 Antigenic Shift Human and avian flu viruses infect same host cell (eg. swine); exchange of segments occurs New subtype of influenza with potential to cause a pandemic may be produced

RNA Haemaggluti nin Neuraminidas e Antibodies bind to haemagglutinin; inhibit infection Antigenic Drift Mutation in haemagglutinin Antibodies can no longer bind to haemagglutinin; infection and disease results

THE “SWINE FLU”: H1N1 (APRIL ) Caused by a strain of influenza A, H1N1 Originated as a mixture of swine, avian, and human influenzas The genetic change that allows a virus to “jump species” is called antigenic shift

SEASONAL INFLUENZA COMPARED TO PANDEMIC — PROPORTIONS OF TYPES OF CASES 26 Asymptomatic Clinical symptoms Deaths Requiring hospitalisation Seasonal influenza Pandemic Asymptomatic Clinical symptoms Deaths Requiring hospitalisation

WHAT WE KNOW ABOUT 2009 H1N1  Infection rate for probable and confirmed cases highest in 5−24 year age group.  Hospitalization rate highest in 0−4 year age group, followed by 5−24 year age group. Pregnant women seem particularly at risk  Most deaths in 25−64 year age group in people with chronic underlying disease. (total about world- wide, most in Africa and Southeastern Asia)  Adults, especially 60 years and old, may have some degree of preexisting protection  There are some predictions that up to 1/3 of the population could have become infected… 27

H1N1/09 virus thought to have originated in Asia mix of swine, avian, and human flu, with pigs as the “mixing vessel” a new vaccine did arrive mid-October was not mutating quickly

Influenza Diagnosis Most often a clinical diagnosis Laboratory tests – molecular detection of virus in clinical specimens – culture of virus – serology Rapid ‘near patient’ tests – detect the presence of flu within 30 minutes – cannot determine the specific virus

Treatment options Let the immune system deal with it If symptoms severe – antiviral drugs

Antiviral drugs Prevent the flu virus from reproducing Treatment can shorten the illness by a day and reduce hospitalisations by an estimated 50% (based on seasonal flu) To be effective, must be taken within 48 hours of the onset of flu symptoms Some common anti-virals for the flu are zanamivir and oseltamivir (Tamiflu)

Prevention 1) Basic measures to reduce the spread of infection Hand washing Respiratory hygiene covering the mouth and nose when coughing or sneezing; using a tissue when possible; disposing of dirty tissue promptly and carefully – bag and bin Avoiding non essential travel non attendance at large gatherings such as concerts, theatres, cinemas, sports arenas etc.

Prevention 2) Vaccines Vaccines can prevent influenza infection, particularly important for the elderly and infants Vaccine coverage is generally poor for infants – less than 10 percent; for the elderly, it can be above 60 percent

Influenza Vaccine Vaccine takes 6-8 months to produce following the emergence of a new virus Supplies will be limited, if available at all – Priority groups are usually established for use of limited vaccine (like who?) – 2nd dose after 30 days will likely be required – Need to monitor vaccine safety and efficacy

Priority groups for vaccinations Children 6-23 months of age Adults >65 years Persons 2-64 years of age with underlying chronic medical conditions Women who will be pregnant during influenza season

Examples of influenza outbreaks

Canada Flu Video deaths-crowe.html

What can we do to prepare ourselves for a pandemic?