Preparing to Survive the H5N1 Avian Flu Pandemic
AVIAN FLU: PANDEMIC PREPAREDNESS
Written and Compiled by Bruce E. Abraham,
December 2005
Advisory Board, King County Long Term Care, Ombudsman Program
Edited by M. Jeanne Cummings, Infection Control Specialist, Harborview Medical Center
Avian influenza, or “bird flu”, is a contagious disease of animals caused by viruses that normally infect only birds and, less commonly, pigs. Avian influenza viruses are highly species-specific, but have, on occasions, crossed the species barrier to infect humans. These viruses have several main types and many subtypes. Most of these viruses are harmless to people because they don’t have properties which allow them to attach readily to human cells. Even if we are exposed to most of these other subtypes, humans are unaffected.
In domestic poultry, infection with avian influenza viruses causes two main forms of disease, distinguished by low and high extremes of virulence. The so-called “low pathogenic” form commonly causes only mild symptoms (ruffled feathers, a drop in egg production) and may easily go undetected. The highly pathogenic form is far more dramatic. It spreads very rapidly through poultry flocks, causes disease affecting multiple internal organs, and has a mortality that can approach 100%, often within 48 hours.
However some avian viruses are “learning” to infect humans (zoonotic). Their surface protein has changed so that it is more compatible with our cells. So far, one specific avian virus (named H5N1) has changed itself (“mutated”) in ways that allows it to infect humans, although it doesn’t do so easily. Nor has it gained the ability to pass easily from one person to another (i.e., it is not very contagious) [as of December 2005].
The World Health Organization has documented more than 130 human cases and more than 70 human deaths caused by avian influenza since January 2004. So far, most human cases appear to have been from bird-to-human transmission only, although some cases of human-to-human transmission are documented and others are suspected.
The term “pandemic” (from Greek, for “all people”) is used to refer to an unusually severe and unique kind of global contagion. The H5N1 virus is expected to continue to mutate. This might make sustained human-to-human transmission possible, allowing the virus to spread easily among humans across the globe (a pandemic).
We live in an age of rapid, global travel. Because adults can be infectious from the day before symptoms begin through approximately 5 days after illness onset it will be near impossible to keep a pandemic virus constrained to any region of the world. Children can be infectious for > 10 days, and young children can shed virus for several days before their illness onset. Severely immunocompromised persons can shed virus for weeks or months. Although the current outbreaks seem to be mostly confined to SE Asia and Indonesia, the situation may change rapidly. Indeed, avian influenza viruses, including H5N1 have recently been found in migratory birds in Russia, China, Croatia, Romania, Turkey, Kuwait and Canada. Migratory bird routes are expected to carry the H5N1 virus to Eastern Africa very soon. Once the virus learns to spread easily from human to human and becomes a pandemic (most disease experts say it’s when, not if), we will be confronting a worldwide public health emergency with potentially hundreds of millions of people infected.
Despite all our medical and scientific advances, we do not have an effective treatment for avian influenza. Nor do we have an effective means to stop a virus from spreading from city to city or across the globe. Furthermore, during a pandemic there will be more sick people than there are hospitals and staff to care for them.
Avian flu is very different from the regular seasonal flu. It’s a different virus, and the regular seasonal vaccine or “flu shot” will not protect you, although all experts agree that getting the current seasonal vaccine is important as protection from the current circulating viruses. It is also important to also get the pneumonia vaccine injection as well. Many of the people who fall seriously ill from flu die of secondary bacterial pneumonia.
The medical histories of those who have already died from H5N1 influenza are disturbingly similar to accounts of sufferers of the Spanish flu in 1918-19. Otherwise healthy people are completely overcome by the virus, developing all of the classic flu symptoms: coughing, headache, muscle pain, nausea, dizziness, diarrhea, high fever, depression, and loss of appetite. But these are just some of the effects. Victims also suffer from pneumonia, encephalitis, meningitis, acute respiratory distress, and internal bleeding and hemorrhaging. An autopsy of a child who died of the disease in Thailand last year revealed that the youth's lungs had been torn apart in the all-out war between disease-fighting cells and the virus, a cytokine storm. There is no effective vaccine that can protect against pandemic flu because scientists will need to first identify the precise strain of virus in order to design a reliable vaccine. The virus is thought not to have yet mutated to a human to human transmission form, therefore a vaccine is not available.
As Dr Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy, summarizes, “The signs are alarming: the number of human and animal H5N1 infections has been increasing; small clusters of cases have been documented, suggesting that the virus may have come close to sustained human-to-human transmission; and H5N1 continues to evolve in the virtual genetic reassortment laboratory provided by the unprecedented number of people, pigs, and poultry in Asia. The population explosion in China and other Asian countries has created an incredible mixing vessel for the virus. Consider this sobering information: the most recent influenza pandemic, of 1968-69, emerged in China, when its population was 790 million; today it is 13 billion. In 1968, the number of pigs in China was 5.2 million; today it is 508 million. The number of poultry in China in 1968 was 12.3 million; today it is 13 billion. Changes in other Asian countries are similar. Given these developments, as well as the exponential growth in foreign travel over the past 50 years, an influenza pandemic could be more devastating than ever before.”
According to US Health and Human Services Secretary Mike Leavitt, a worst-case scenario projection, based on the 1918 pandemic, six weeks after an H5N1 pandemic arrives in the US, we will see 722,000 pandemic cases in the United States, by week nine -- 37.4 million, by week 12 -- 90.8 million, and by the end of week 16, 92.2 million cases.