30 May 2013
Flu infections follow seasons, typically rising in winter and dropping in summer. As it moves, a virus mutates, with the risk that with every new flu season, a highly infectious virus could come back more deadly than before. We struggle between the hype of a new disease and the potential threat it imposes.
In 1918, shortly after the end of the first World War, the deadly Spanish flu (H1N1) swept around the world, killing an estimated 50 million people in just under 2 years, more than the number of people killed in the 4 years of war preceding it. South Africa was among the countries most affected, with an estimated 500,000 deaths. Many people who got infected succumbed fast, dying within days of getting sick. Today there is concern that, with the right conditions, we could soon face a similar pandemic.
Viruses are extremely efficient - they sneak past the host’s defense system and implant themselves inside cells, using their machinery to copy themselves endlessly. In one day, a single virus can make millions of copies of itself. Once they’ve depleted the cell’s resources, they burst it open, releasing a swarm of viruses ready to infect nearby cells.
The deadliness of a virus depends largely on two things - how good it is at infecting cells, and how good our defenses are at detecting it and wiping it out before we succumb to the disease. Not all viruses are trying to kill us. The ones that do are just too good at copying themselves, and our defenses are too slow to catch them. But generally, our immune systems are good at recognising new infections, attacking them, and remembering those invaders for the next infection. That’s why if we get flu one season, we don’t get sick the next; our immune system can detect and fight off the virus. Each year, about 0.1% of people with flu die, although this varies depending on the virus. With Spanish flu it was much higher with estimates ranging from 1 to 2%.
To defeat our immune systems, viruses mutate. They keep themselves one step ahead of our inner sentries by constantly changing themselves, becoming difficult to recognise. If two different viruses end up in the same cell, their DNA can mix together like a deadly cocktail, creating a new virus. This is why viruses end up with different names like H1N2, H5N1 - the names reflect the mixing and matching of different parts of the virus that scientists can trace by sequencing the viral genes.
Flu infections follow seasons, typically rising in winter and dropping in summer, with the changes in temperature. As it moves, a virus mutates, with the risk that with every new flu season, a highly infectious virus could come back more deadly than before.
Most viruses are only able to spread between the same species - from human to human or bird to bird. But sometimes the virus mutates in just the right way to allow it to jump between species. The reservoirs of viruses in livestock animals like pigs and birds are the most likely place where a potentially deadly virus will arise and get passed onto us. The 2009 swine flu pandemic was caused by a new strain of the influenza virus, a grandchild of the Spanish flu virus, and was a mixture of viruses from pigs and birds.
Organizations like the World Health Organisation (WHO) and the Centres for Disease Control (CDC) are constantly alert to these jumps from animals to humans. Swine flu spread quickly, causing about 17,000 deaths after 6 months and the WHO declared it a pandemic, scaling up research and treatment campaigns to prepare for its resurgence in the next flu season. But by then, the disease had dropped back to typical seasonal flu patterns and was no longer a major threat.
Currently, two outbreaks are being closely monitored. Since February, the newest flu H7N9 has left 36 dead and 131 infected in China and a single infection in Taiwan. Its origin is not exactly known, but it was introduced to humans through birds and doesn’t seem to spread from human to human. The WHO has already sequenced the viral genome, and is working on a vaccine. The number of new cases is dropping, but WHO reports say that this virus has a higher potential to spread from human to human than other known bird flu viruses.
The second virus is a coronavirus, similar to the SARS virus that caused a massive outbreak in South-East Asia, Taiwan and China ten years ago. This new outbreak in the Middle East is raising red flags because it is spreading from human to human, although not very well.
Because viruses adapt so easily, it is hard to predict what course these two diseases will take. Each time a new influenza or coronavirus is detected, we have no idea whether we’re looking at the birth of a pandemic. Currently, our best hope is to monitor new cases, contain the spread of the disease, figure out which type of virus is causing the disease and try to create a vaccine as soon as possible. With the 2009 outbreak of H1N1 we managed this successfully, but there still isn’t an effective and safe vaccine for SARS.
Meanwhile, we struggle between the hype of a new disease, especially with our instantaneous access to news, and the potential threat it imposes. With each new outbreak, the decision has to be made whether to use our energy and resources to treat this like a health emergency, or as just another seasonal flu. Not only are the outbreaks risky for us, but they can strike the economy hard due to the loss of livestock through mass slaughtering to contain the disease, or in lost revenue.
The WHO underwent heavy criticism for declaring the 2009 H1N1 outbreak a pandemic with complaints that it was over exaggerated and caused unnecessary panic. It has been suggested that the WHO was pressured by drug companies who stood to make a profit off the stockpiling of vaccines. But amidst the hype and hysteria, we can’t afford to become immune to news about these new viruses. They pose a real threat, and we must be constantly prepared for what they might become.