Influenza Pandemic Planning

The NZ Primary Health Care Online Training Course

Welcome!

This course aims to provide the best possible information for Influenza Pandemic Planning in New Zealand and to equip practitioners with a firm platform of knowledge, and keep it relevant at all times in order to foster professional growth.

Key Course Objectives

Learning Outcomes

Summary of Key Issues

Influenza Viruses

Influenza A viruses are found in many animal hosts and can potentially cause global (pandemic) influenza outbreaks, whereas types B and C only affect humans and do not cause pandemics.

Influenza A viruses are classified by subtype on the basis of the two main surface glycoproteins hemagglutinin (HA) and neuraminidase (NA). Click here for full topic...

Seasonal, Avian and Pandemic Influenza:

Avian:

Avian influenza ('bird flu') - eg type A subtype H5N1 - is a disease of birds which does not usually infect people, although it is clear that it can in some circumstances. The concern about the current epizootic of H5N1 in bird populations in Asia is that the virus could change to be able to pass from person-to-person and cause a pandemic, because there is no pre-existing immunity in humans to this new virus. It is not clear if, when or how long this process of adaptation would take.

Pandemic Potential:

The H5N1 virus could improve its transmissibility among humans via two principal mechanisms:

The first is a "reassortment" event, in which genetic material is exchanged between human and avian viruses during co-infection of a human or pig. Reassortment could result in a fully transmissible pandemic virus, announced by a sudden surge of cases with explosive spread. This was the mechanism leading to the viruses causing the 1957 and 1968 influenza pandemics.

The second mechanism is a more gradual process of adaptive mutation, whereby the capability of the virus to bind to human cells increases during subsequent infections of humans. Very recent genetic analysis of the 1918 influenza virus suggests that the 1918 virus was not a reassortment virus (like those of the 1957 and 1968 pandemics), but more likely an entirely avian-like virus that adapted to humans, ie was able to cross the species barrier. This virus resulted in an unknown number of deaths worldwide but estimated at 50 - 100 million deaths, 8250 deaths in NZ, and shortened life expectancy by 13 years in the USA. The greatest impact was in the 20-40 year age group.

H5N1 Potential:

Given the unprecedented number of birds infected with H5N1, the fact that so far there have only been 165 (to the end of January 2006) confirmed human cases shows the low (direct) risk from avian influenza to humans so far. Over half of those with confirmed H5N1 infection have died. However, if the virus mutates to a human form, it is likely to become less lethal - the New Zealand planning model, based on the 1918 pandemic, assumes a 2% case fatality rate.

Risk in NZ:

If avian H5N1 enters NZ via an infected bird there is little direct human health threat as long as the virus does not establish itself in bird populations in NZ. Click here for full topic...

New Zealand Pandemic Planning

Scenarios used to gauge the potential impact of an influenza pandemic in NZ estimate a maximum 40% incidence, potentially resulting in 83 influenza consultations per GP/week (likely more owing to GP sickness) over an 8 week period (compared with a usual death rate of 4,400). Note: that the pandemic is not linear, but rates peak in the middle weeks.
Click here for full topic...

Primary Health Care Preparedness

Transmission of influenza occurs by either droplets or direct contact. Overall "hand hygiene" is the single most important measure to reduce the risk of transmission. Other infection control measures in the surgery include:

• Keeping 1 metre distance
• Wearing a surgical mask (dependent on level of risk)
• Adequate ventilation
• Cough etiquette
• Availability of personal protection packs for use when there is high risk of aerosol spread of respiratory secretions

Being prepared:

• Encourage influenza vaccination in all staff and eligible patients. Although this is unlikely to protect against pandemic influenza, vaccination will protect against seasonal influenza, which is a significant cause of morbidity and mortality in New Zealand
• Be on alert for an index case
• Have an information sheet available on the use of Tamiflu^®
• Plan stocks of masks, gowns, gloves, tissues, antibiotics, etc
• Keep 2 higher level personal protection packs
• Train all staff in infection prevention and control
• Establish procedures for dealing with patients who have relevant symptoms and a history of travel to an affected country
• Consider how to operate with reduced staff
• Share your planning with the community

During a pandemic:

• Encourage patients to ring instead of presenting at the practice if suspected of suffering from pandemic influenza.
• Use strict infection control procedures
• Staff who have influenza symptoms must stay away
• Ensure security considerations are properly addressed in an environment of panic and desperation (particularly with regard to stocks of drugs such as antibiotics and antivirals).
• Click here for full topic...

Anti-Viral Drugs

H5N1 influenza virus has been shown to have resistance to amantadine, which is unlikely to be effective.

Tamiflu^® (oseltamivir) can be used for either treatment or prophylaxis (75mg bd for 5 days for treatment, one cap daily for prophylaxis). Its effectiveness against H5N1 has not been tested in vivo although it has been shown to be effective against the virus in the laboratory. Final policy on priorities for the use of Tamiflu can only be made once the epidemiology of the pandemic strain is understood, but it is currently planned that, in accordance with WHO advice, Tamiflu will be predominantly used for the treatment of cases, although at an early stage when attempts are being made to stamp out small clusters it may be administered to contacts of cases or suspect cases in an effort to reduce spread. The drug is ineffective if given more than 48 hours after infection. Early usage (within 48 hours) is therefore crucial. The drug appears generally safe with the most common side effects being transient nausea, vomiting, abdominal pain, and headache. Based on studies of its use for seasonal influenza, it reduces viral production and shedding, shortening the duration of the illness. Click here for full topic...

Vaccines

Current influenza A vaccines are unlikely to offer protection against a new pandemic strain. Although New Zealand has an agreement in place for access to vaccine against a future pandemic strain, there would be a delay of at least 15-27 weeks between identification of a pandemic and the arrival of a vaccine. 2 doses of vaccine are likely to be required with up to 4 weeks between courses, but trials are still in progress. Vaccine manufacturers are developing a "prototype" vaccine to the current H5N1 virus which may offer some protection against a future pandemic strain. Click here for full topic...