The Origins of the Avian Flu
It sounded like the plot of a made-for-television movie. In the remote corner of China, a group of villagers developed a severe, rapidly fatal respiratory infection. The source of the illness is traced to a virus that normally affects birds. Officials are relieved to see that it only affects villagers exposed to sick birds and did not spread from person to person. They feel comfortable that they have contained the outbreak by destroying flocks of infected birds. Then the same disease appears in other regions in China and then jumps to Indonesia. Health care officials realize that migrating birds are spreading the virus across Southeast Asia — and soon would carry the infection throughout the world.
In recent years, it has been hard to pick up a newspaper or turn on the TV without yet another story of bird or avian flu. Since it first appeared in China in 1997, avian flu has infected birds in 48 countries in Asia, Africa, and Europe. It has caused devastating illness in people in seven countries in Southeast Asia, as well as in Egypt and Turkey. Over 200 children and adults have been stricken and more than 100 have died — a mortality rate of more than 50 percent.
Adding to the concern is the discovery that the infamous influenza epidemic of 1918 was caused by a form of avian flu. Health officials around the world have put into place increased viral surveillance as well as established public health strategies to contain an outbreak if it should develop in a country. When the Bush Administration issued an executive order that allowed officials to declare a state of quarantine should it be needed, it was a sobering reminder of just how seriously experts regarded the threat.
Are we really on the verge of an avian flu pandemic? Many of the critical signs are certainly there. An animal virus suddenly becomes lethal to man. Pandemics come in cycles and we are definitely overdue for this type of worldwide outbreak. On the other hand, there have only been 200 cases in humans. Is the anxiety the result of an overactive imagination on a slow news day? The truth lies somewhere in between.
Avian Flu 101
Avian flu is a form of influenza that until recently only affected birds. When an animal virus becomes compatible with man, the virus undergoes a number of genetic changes, all bad. It tends to produce extremely severe illness that attacks a wide number of organs in the body. Given the pattern of a genetic shift in the influenza virus, doctors are concerned that the current status of transmission of avian flu from bird to human will change to human transmission.
Most cases of avian flu are seen in people who had direct contact with infected poultry. It is believed that the bird flu is spread by contact with sick poultry. Farmers and those who work in poultry processing plants are currently at the highest risk of contracting the disease. There have been less than a dozen cases where the disease has been spread from person to person. In the spring of 2006, a family of seven died from avian flu. Doctors were especially concerned because it was the first time that the infection had spread to others twice removed from contact with a sick bird.
In fact, one of the most puzzling aspects of avian flu is its low level of contagion between people. Researchers at the University of Washington suggest that the difficulty in people to people transmission virus is linked to the fact that the virus likes to grow in cells that are found in the lower lungs. The deep-seated infection means that it is less likely to spread by sneezing or kissing, slowing the spread of viral particles. However, the viral growth in the lower airways also is one of the reasons that avian flu is such a severe illness.
While this is somewhat reassuring, scientists know that the influenza viruses are relentlessly changing. There is a deep concern that with a few small changes in the genetic code, the avian flu virus will start to flourish in the upper airways. With this type of development, the infection could be easily spread by sneezing and coughing. Even a used tissue could be the source of millions of infectious viral particles.
Symptoms of Avian Flu
I am waiting for the first call from a patient who fears that they have come down with avian flu. While even the garden variety of annual flu can make you feel truly awful, the symptoms of avian flu are dramatic and overwhelming. It begins with a high fever, severe diarrhea, and a cough. Within a few days, avian flu victims develop shortness of breath and bloody sputum. On x-ray, the lungs have all the signs of viral pneumonia. Severe respiratory distress follows and the kidneys and heart begin to fail. Avian flu affects people of all ages but is particularly severe in children.
The Good News about Avian Flu
In light of the very real concerns of an impending epidemic, it is reassuring to see the worldwide mobilization of health care resources. At this point, our best defense is a strong offense with heightened surveillance and rapid, comprehensive response to signs of flu in both birds and man. Avian flu is not a silent disease in poultry flocks. Reports of sick and dead birds activate teams of investigators that test for the presence of the virus. To prevent the outbreak from spreading, entire flocks in the region are destroyed and healthy birds are vaccinated against the disease.
So far this approach of surveillance and containment has been working. In Thailand and Vietnam, there has not been a single human death this year from avian flu. In Africa, where the lack of health care resources and infrastructure were felt to be a weak link, there has not been an explosion of disease among domestic flocks that are so essential for the African economy.
Preventing and Treating Avian Flu
Even more encouraging has been the progress in the development of a vaccine. There are over 30 different types of avian flu vaccines now in development. The first vaccine has been tried in more than 1,000 people. While it seems safe, it is not particularly effective. The routine dose of the annual flu shot is 7.5 units and is up to 90 percent effective in adults under the age of 65. Unfortunately, even 150 units of the prototype of the avian flu vaccine is only 40 percent effective. Given that, we can barely produce sufficient quantities of the annual flu vaccine, this new vaccine cannot be made in sufficient quantities to protect large numbers of the populations.
Vaccine Development
The threat of a deadly epidemic has actually focused long-needed attention on vaccine development and production. One of the most interesting developments is the addition of compounds to the vaccine that improve its performance. Called adjuvants, they can raise the efficiency of a vaccine so that lower doses can be used and more people can be protected. Another exciting area of research is the development of a universal influenza vaccine. Currently, flu viruses change enough each year to require a new formulation, and each year there is an anxious scramble to produce sufficient quantities of an effective vaccine. A universal vaccine will be able to protect against the genetic make-up of the viruses. Without the need to remake the vaccine from scratch each year, the flu vaccine shortages will no longer be an issue.
Testing
Fear of an avian flu pandemic has also stimulated new diagnostic technology. We now have an effective test for avian flu that provides results in several hours. Not satisfied with the wait, virologists are working on a test that will show results in a matter of minutes. The new techniques that are being developed for this test will then be used to help us diagnose other new infections as they arise.
Antiviral Treatments
There have been equally impressive developments in the search for effective antiviral treatments. Doctors are aware that Tamiflu has shown an ability to reduce the spread of the avian flu virus. It can be used to protect people exposed to the flu virus as well as to treat those who are already infected. Governments throughout the world have rushed to stockpile Tamiflu, but the drug is expensive and in extremely short supply. The patent is held by just one company and the manufacture of this drug is time-consuming, complicated, and even has a step that can explode. Tamiflu starts with a spice called star anise that is in relatively limited supply. Star anise is a licorice-tasting seed, grown only in China and harvested only from March to May. It is the only source of shikimic acid, the first essential ingredient in the production of Tamiflu.
It has been truly exciting to watch scientists investigate and come up with new ways to produce Tamiflu. A researcher at the University of Michigan has been able to produce shikimic acid via fermentation of genetically engineered bacteria. At Harvard, a scientist starts with two very inexpensive and common ingredients that actually avoid dangerous and explosive steps in Tamiflu production.
Medical Advancements
As we look at the disturbing, grainy photographs of the 1918 influenza epidemic, it is important to recognize that the current worldwide, early warning systems now in place certainly have dampened the natural course of epidemic disease. In 1918, we did not even know that influenza was caused by a virus. There were no vaccines, no antibiotics, nor diagnostic tests. Advances in surveillance and communications have interrupted the spread and mortality characteristic of past epidemics. They may not have eliminated or even contained avian flu, but these strategies have brought us valuable time to develop better vaccines and treatments and organize public health measures if and when the avian flu becomes pandemic.
The Danger at our Doorstep
As we anxiously scan the skies for the birds that could bring avian flu to the Americas, we should not forget the very real dangers that the annual flu brings to our communities. It is important to remember that each year, the flu affects up to 60 million Americans, puts 400,000 in the hospital, and is fatal to over 20,000. Much of this death and disease can be prevented with a single yearly flu shot, but a disturbing number of Americans choose not to be immunized. Only about 60 percent of older adults line up for the shot, while just 12 percent of younger adults at risk for complications get the protection they need. Even more troubling, less than 40 percent of health care professionals are immunized against influenza.
We are absolutely right to be concerned about the possibility of a deadly avian flu pandemic. We should be at least as concerned about protection for the annual influenza outbreaks that we know will appear in our community each fall. If you take just one idea away from this article, let it be the need for an annual flu shot for the whole family.
