“For the first time in history, we have the opportunity to prepare,” remarked Dr. Kristy Duncan, a medical geographer at U of T. Past pandemics have caught us by surprise, but the scientific community believes modern science will help us predict new viral threats before they explode across the map.
A pandemic is a disease outbreak that affects a large proportion of the population of a continent or the entire world. Avian influenza, or H5N1, has been flagged as the next pandemic threat because it has already killed several people who have caught the virus directly from birds. Currently, 50 per cent of those infected with H5N1 die.
Avian influenza infects deep areas of the lungs, eventually causing pneumonia in human patients. Since it infects deeply enclosed tissue, the virus isn’t expelled by coughing or sneezing, and isn’t transmissible between humans. But if H5N1 gains the ability to infect the upper respiratory tract, this will spell pandemic for human populations.
Influenza strains evolve the ability to infect humans by mixing their genes with other influenza strains. Pigs, which can be infected with both human and bird influenza viruses, are perfect vessels for this mixing. Humans will have no immunity to the new virus, a factor that would make it incredibly dangerous.
The H5N1 pandemic may occur any time from the next few months to fifty years from now, if it occurs at all. The aim of today’s public health strategies is not to stop the virus (which is impossible), but to slow its spread until a vaccine is developed.
Vaccines and anti-viral medication are our two trump cards if bird flu evolves into a widespread killer. Though vaccines are the most effective preventative tool against viruses, a vaccine for H5N1 can’t be developed until the virus has evolved to its killer form. TamiFlu, currently the most effective anti-viral medication, is being stockpiled in preparation for a pandemic. However, viruses can develop resistance to drugs the same way bacteria do to antibiotics, creating a race to develop newer anti-viral treatments.
Some infectious disease specialists believe that H5N1 may become less virulent once it becomes easily transmissible between humans. From the virus’s perspective, killing its victim quickly would render it homeless and is therefore a bad strategy. If the virus moves to the upper airways it can be spread more easily, but becomes less harmful, since the air-conducting channels in the upper airways are less sensitive than the delicate alveoli deep down.
Another factor to consider is how well the virus can survive outside a host. Currently, H5N1 can live for up to two days on a clean surface, meaning a person can pick up the flu from a door handle or bathroom tap contaminated up to two days ago.
Compared to influenza, the Ebola virus has gained much public attention because of its devastating effects (killing up to 90 per cent of those infected), but doesn’t loom as large a threat. It kills its victims too quickly for them to transmit the virus and doesn’t survive long outside the body. Ebola also isn’t transmitted through the air, but through contact with bodily fluids. Because of this, Ebola outbreaks have so far been confined to one country at a time.
Viruses aren’t the only microscopic particles that can cause pandemics. Creutzfeld-Jakob disease (CJD) is a prion disease in humans. A variation of the disease called vCJD (variant CJD), can be contracted by eating beef contaminated with bovine spongiform encephalopathy, commonly called mad cow disease. Unlike viruses, prions have no genetic material and are formed from a protein that is naturally present in the body. Proteins become infectious prions if their natural configuration is changed in a certain way. The abnormally shaped, diseased prion can spread the transformation to other normal proteins they come into physical contact with.
The danger of a prion pandemic is relatively small because infection is limited to ingestion of tainted meat, certain medical procedures, and hereditary transmission. Prions do have two secret weapons: a long dormant period and extreme durability. A person can be infected for up to 20 years before showing signs of the disease, and prions can only be destroyed by extreme methods like an hour-long bleach soak.
Ebola and prions are “sexy” diseases for sensational media stories, but less exciting and more dangerous threats to human health also need consideration. The most insidious dangers to humanity now include drug-resistant strains of tuberculosis and Staphylococcus aureus. These bugs aren’t killed by the antibiotics we’ve come to rely on, and they account for an increasing number of hospital-acquired infections.
As of yet, influenza has not reached pandemic proportions, but remains a serious health concern.
Modern science and medicine aim to protect humans from natural biological threats, but a medical approach that neglects history and geographic factors is incomplete. Applying our knowledge of infectious diseases from past pandemics will give us the best chance of surviving the next one.
