2 Strengthening Preparedness for Pandemic Influenza Flashcards
Overview Summary
This session provides an overview of preparedness for pandemic influenza. In the introductory session, you learned about what constitutes a global health policy issue. In this session, you will apply the concepts learned in the previous session to the issue of pandemic influenza.
Overview Aims
The aim of this session is to provide students with an understanding of the global dimensions of pandemic influenza; why combating this particular disease is important; the contemporary governance mechanisms aimed at preventing and controlling this disease; and the key issues inhibiting and/or facilitating collective action to strengthen preparedness.
Overview Learning outcomes
By the end of this session, you should be able to: 1 Understand the nature, epidemiology and history of the influenza virus; 2 Analyse the various factors that contribute to and/or mitigate the risk of pandemic influenza; 3 Identify the key actors and institutions in global efforts to control and mitigate the threat of pandemic influenza; 4 Assess national measures to enhance pandemic influenza preparedness; and 5 Explain the contemporary debates/issues inhibiting effective governance of pandemic influenza.
Key Terms Antigenic drift
This occurs when there is a minor change (mutation) during virus replication in the same sub-type of the influenza virus, resulting in a new strain of the virus emerging.
Key Terms Antigenic shift
This occurs when there is a major change during virus replication resulting in an entirely new sub-type of the influenza virus emerging that may or may not be capable of crossing the species barrier, but which has pandemic potential.
Key Terms Antiviral medication
A category of medication that is used to treat viral infections (such as influenza) by inhibiting viral replication. This is usually accomplished through preventing the virus from entering and infecting cells.
Key Terms Case Fatality Rate (CFR)
The ratio of the number of deaths caused by a specific disease divided by the number of confirmed diagnoses of that disease.
Key Terms Influenza
A viral infection of the nose, throat and lungs (respiratory infection) caused by one of three sub-types of an RNA virus (Type A, B or C).
Key Terms Influenza vaccines
Biological preparations developed using deactivated or partially live influenza viruses for the purpose of conferring immunity against influenza by stimulating the human immune system to identify the virus as a foreign entity.
Key Terms Pandemic influenza
A pandemic is the worldwide spread of a new disease. An influenza pandemic occurs when a new subtype of the influenza virus emerges to which humans have little to no immunity, that is easily transmissible between humans and causes serious illness.
Key Terms Social distancing measures
Non-pharmaceutical infection control measures. These can include quarantine, isolation, school closures, face masks, cancellation of mass public gatherings.
- Background
An influenza pandemic occurs when a new strain of influenza virus spreads around the world to which most people do not have immunity. Viruses that have caused past pandemics typically originated from animal influenza viruses. Although rare, influenza pandemics are a regular feature of human existence and are likely to remain so until the elusive (and perhaps impossible) goal of a universal flu vaccine is achieved. Every year, millions of people are exposed to seasonal influenza viruses, but in most cases these viruses only cause mild to moderate illness. For an influenza pandemic to happen, a new sub-type of the virus must emerge to which humans have little or no immunity, and which has the potential to cause severe illness. A pandemic can occur when this virus then achieves effective human-to-human transmission, meaning that it can spread easily amongst people.
- Background
The World Health Organisation (WHO) has been at the forefront of efforts to prepare the international community for another influenza pandemic. The WHO’s Global Influenza Surveillance and Response System (GISRS) is the foundation of the contemporary global influenza governance system. The GISRS brings together scientists and public health professionals based in laboratories and influenza research institutions around the world to share information and data, isolate viruses, and determine which strains of the virus are circulating. The information generated by this network is then used to inform the development of influenza vaccines, which offer the best protection against becoming infected with influenza.
- Background
Influenza vaccines provide the best protection against infection so the WHO has encouraged governments to secure access to influenza vaccines as part of their contingency planning. The core problem, however, is that global production capacity of influenza vaccines is limited, and it currently takes months to develop vaccines against specific virus strains (such as a new pandemic strain). Anti-viral medications may help to reduce the severity of illness, and non-pharmaceutical measures can assist in preventing infection, but vaccines continue to offer the best protection. Every government around the world has been encouraged to develop, and then exercise, a national pandemic influenza preparedness plan in order to limit the social disruption and loss of human life that may occur from an influenza pandemic. In this section we will give a brief explanation of the history and epidemiology of influenza to show why it is such an important threat to global health. The following sections will then discuss the efforts being made to prepare and respond to this threat at international and national levels.
1.1 Brief history of influenza
Influenza is one of the oldest diseases known to humans. The first documented influenza epidemic in Europe occurred in 1173 CE. There were many other epidemics over the next 400 years, but it is generally accepted that the first influenza pandemic took place in 1580 [Potter 2001]. Since then, documentary evidence reveals that pandemics have occurred with regular frequency. In the 20th century there were three major influenza pandemics, the worst in 1918 which killed tens of millions of people. For centuries, medical practitioners did not know how influenza spread. Early theories suggested that the disease was spread through foul-smelling air, or miasma, or that it was caused by meteorological or telluric conditions such as solar flares, rainfall, or even volcanoes and earthquakes. In the late 19th century, a new theory emerged that the disease was actually spread by microscopic agents that were too small to be seen by the human eye but the debate was not truly concluded until 1933 when a group of scientists isolated the influenza virus from pigs. An effective vaccine to protect humans from influenza was not developed until the 1940s.
1.2 Basic epidemiology of the influenza virus
As you may be aware, influenza is a respiratory infection of the upper respiratory tract – usually affecting the nose, throat and lungs. Importantly, influenza is a disease common to humans, but it is also frequently found in both pigs and birds. Less well known is that it is a disease that also affects whales, horses and seals.
1.2 Basic epidemiology of the influenza virus
Transmission of the influenza virus in humans most commonly occurs when there is direct contact with respiratory secretions from an infected person, usually in the form of coughing or sneezing. The influenza virus is a fairly hardy virus and is capable of surviving outside the human body for up to 48 hours. This means it can live for a period on inanimate items such as door handles, tables, and so on. Another name for these inanimate objects is fomites.
1.2 Basic epidemiology of the influenza virus
Symptoms usually start to appear between one to four days post exposure and commonly include coughing and sneezing accompanied by a fever. Lethargy or tiredness, muscle pains and headaches are also commonly experienced. Individuals with the influenza virus will usually be infectious for one to two days before symptoms appear, and up to five days after symptoms appear. Most people usually recover within one to two weeks. Although influenza is often confused with other illnesses such as the common cold, influenza is far more serious, as it has the potential to overwhelm the body’s immune system which can lead to more life-threatening conditions.
1.2 Basic epidemiology of the influenza virus Subtypes of Influenza
Following the isolation and identification of the influenza virus in 1933, scientists identified three main types of the virus (and numerous sub-types), which have been named A, B and C.
1.2 Basic epidemiology of the influenza virus Subtypes of Influenza
Type A - Type A influenza is known to be the most dangerous for humans. It is also found in pigs, birds and other mammals. This ability to infect a wide range of animal hosts as well as humans means that the virus has ample opportunity to mutate and change. Type A virus is often the virus that is responsible for causing epidemics and pandemics.
1.2 Basic epidemiology of the influenza virus Subtypes of Influenza
Type B - Type B influenza has been found in seals but is otherwise believed to be exclusive to humans. The limited number of hosts means that the virus has less opportunity to change. Type B has been identified as being responsible for occasional epidemics in humans, but historically these have been relatively mild.
1.2 Basic epidemiology of the influenza virus Subtypes of Influenza
Type C - Type C influenza is the rarest. It is believed to be found in pigs and dogs as well as humans, but generally will only cause mild respiratory illness.
1.2 Basic epidemiology of the influenza virus Subtypes of Influenza
Most viruses are DNA based, so that every time these viruses copy themselves, the new virus is identical to the first. But influenza is an RNA-based virus, which means that it is much more prone to mutation when it replicates.
1.2 Basic epidemiology of the influenza virus Structure of Influenza A virus
Figure 1 shows a simplified image of the influenza A virus as if it has been cut in half through the middle. The pink and purple stripes that surround the virus represent the proteins on the surface of the virus: neurominidase (NA) and hemagglutinin (HA) which the virus uses to attach itself to another cell so it can then invade that cell.