In 1918 the Spanish Flu (named after the country of origin of the first reported case) swept the globe, killing 20-40 million people – more than the First World War (which killed 15 million) which was just ending. When an epidemic spreads to multiple regions, especially multiple countries or continents, it becomes a pandemic. Flu pandemics happen 2-3 times each century.

This is probably partly why there has been so much news attention, even some mild hysteria, surrounding recent outbreaks of swine flu, beginning in Mexico. It is hard to say how many cases and how many deaths there have been so far, because information from Mexico is spotty. Specifically it is difficult to say if people who have died with flu-like symptoms really had the swine flu or something else.

Estimates are that more than 800 people have contracted the swine flu in Mexico with 29 confirmed deaths, although none in the last week.  The Centers for Disease Control (CDC) reports as of May 5th that there have been 403 confirmed cases in the United States, with the first death just reported. World-wide there have been 1,490 cases in 21 countries (according to the World Health Organization– WHO).

Some Background on Influenza

The influenza or flu virus is an RNA virus that comes in three genera – A, B, and C. Influenza A is the most common type. It can infect mammals and birds, with aquatic birds being its natural endemic host. Each year there is a seasonal epidemic of Influenza A, infecting millions of people world-wide and killing 100-200,000 – mostly the very old, the very young, and the sick.

Influenza B is less common than A and infects only humans, seals and ferrets. Influenza B mutates slower than A, and so has less genetic diversity and is less virulent as a result. Influenza C infects humans, dogs, and pigs and is the least common type, but can be virulent when outbreaks occur.

All of the pandemics over the last century have been of Influenza A. Its primary weapon is its ability to rapidly mutate, avoiding the immune systems of its hosts. This is why each year new strains of Influenza A are causing that season’s epidemic.

The flu starts out like a common cold, but lasts longer and becomes more severe. It is characterized by high fevers, muscle aches, fatigue, headache, and severe cough.

Influenza A strains are designated by the two main proteins that determine their infectivity and virulence -haemaglutanin and neuraminidase, H and N. There are 16 Hs but only H 1-3 infect humans, and there are 9 Ns but only 1 and 2 infect humans. Haemaglutanin is a protein that allows the virus to latch onto and infect host cells, while neuraminidase allows expelled viruses to reinfect other cells.

The flu is potentially a fatal illness, killing about 1% of those infected. Death results from one of three types of causes – the flu infection itself can cause a serious pneumonia (lung infection) that can impair breathing to the point of death. A serious infection can also leave someone open to a superinfection (another organism causing a second infection while the host’s immune system is occupied with the flu). And those who have a chronic underlying illness may succumb from the added physiological stress added by the flu.

The Current Swine Flu

The swine flu virus is Influenza A H1N1. This strain came about probably by four different strains of Influenza A infecting the same host (probably a pig, hence the name swine flu). Viruses can exchange genetic material, so one strain can combine bits from other strains, creating a new strain. The current swine flu likely combined bits from a human virus, a bird virus, and two swine viruses, although this is still being confirmed.

Further, there are 8 gene segments in the Influenza A virus that can be shared among different strains. Typically these reassorted viruses are weak strains when they first come into existence. Their genes have just been mixed, with unpredictable results, and they have not yet had time to optimize the new assortment. But once these new viruses start spreading they evolve quickly as they are fine-tuned by selective pressure to be more infective and hardy.

It is not yet clear how the current H1N1 became so virulent so quickly – it is already adapted for human-to-human spread. It is also not clear if it has the potential to cause a pandemic. We do not yet know what specific mutations allow an Influenza virus to cause a pandemic so even though we have isolate the virus we cannot directly tell how dangerous it is. Likely this strain will need to undergo further mutations in order to have pandemic potential. However, during an outbreak, when the viruses is rapidly multiplying and spreading, it mutates quickly, increasing the chance of a mutation to pandemic potential.

Should We Worry

This week on the SGU we interviewed Mark Crislip, and infectious disease doctor, host of Quackcast, and one of the authors here at Science-Based Medicine. We discussed in detail the latest swine flu outbreak, and what level of concern is currently appropriate. The bottom line is this – this is a new strain of flu virus which appears to be spreading. It is not yet known if it has the capability of producing a world-wide pandemic, but it might and if it does it could theoretically rise to the level of the 1918 pandemic which killed millions. Some of the reported deaths from Mexico were young healthy adults (which was also common in the 1918 pandemic), which can mean that the strain is virulent.

But it is too early to tell. This epidemic may also fizzle out quickly, ultimately affecting very few. In 1976 there was a swine flu epidemic with concerns that it would be the next big pandemic, but it just fizzled and amounted to nothing.

What determines whether this latest strain with be a bang or a bust is how infectious it is (how many people with catch the virus) and how virulent it is (how may infected people will die from the infection). We do not yet know how this current swine flu will behave – we don’t have enough data points yet. Probably we will not know until the pandemic is underway, or until after it has burnt itself out.

At this point in time there is no reason to panic or make major changes in your lifestyle. The WHO and the CDC are watching closely and will make recommendations. At present the CDC recommends the following:

People who are sick are urged to stay home from work or school and to avoid contact with others, except to seek medical care. This action can avoid spreading illness further.

That’s it – they are not recommending that we limit international travel or that we start shutting down schools. Essentially, if you have a cold or flu-like illness, don’t tough it out and go to work – stay home and seek medical care if necessary.

The WHO has similar recommendations. They are not recommending limiting travel at this time. While not explicitly recommending the use of masks in public, they also provide guidance as to how to properly use a mask. The same document also details general recommendations to avoid spreading the infection – wash your hands, keep a meter away from symptomatic individuals, stay home if you are sick.

Mexico, which has been hardest hit so far, shut down schools, museums, and public places for 5 days. They even canceled their Cinco de Mayo celebrations. However, they claim that new cases in Mexico are already past their peak and therefore the epidemic is slowing down. They have lifted their restriction and are trying to get their economy back on track.

That is where we are today. If the infection continues to spread and show signs that it is developing into a pandemic, the WHO and CDC will update their recommendations. There are some possible signs already that this outbreak will not be the next major pandemic. Early numbers indicate that this strain is no more infectious or virulent than the usual seasonal flu strains.

However, some warn that we are not yet out of the woods. New cases are still being reported.  The WHO also pointed out that in the 1918 pandemic there was a second wave of a more virulent strain of the virus, and it was this second wave that caused the pandemic. So we may be in store for a second wave of H1N1 in a couple of months.

Perhaps the most alarming warning I have read comes from Yi Guan, who is famous for identifying the SARS virus in 2003. In a recent interview he criticized the WHO for not reacting quickly enough to the outbreak in Mexico. He says:

WHO should have gone to level 4 or even level 5 on Friday. We missed the golden period to contain the virus. Several hours could be another couple hundred cases. Every second was valuable at that time. We made a huge mistake. From then on, it was countdown to the pandemic.

Guan also warns that the H1N1 may combine with the H5N1 strain, which has a 50% mortality rate. He says this is very  very unlikely, but if it does happen it will be a “nightmare for the whole world.”

Therefore at present the ultimate fate of H1N1 will be determined by how it mutates and combines with other strains – unpredictable events. At this point all we can do is monitor the outbreak closely and react accordingly.

There are treatments for the swine flu. This strain will respond to certain anti-viral drugs, which may decrease the severity of the illness and decrease the mortality. The CDC has this to say:

There are four influenza antiviral drugs approved for use in the United States (oseltamivir, zanamivir, amantadine and rimantadine). The swine influenza A (H1N1) viruses that have been detected in humans in the United States and Mexico are resistant to amantadine and rimantadine so these drugs will not work against these swine influenza viruses. Laboratory testing on these swine influenza A (H1N1) viruses so far indicate that they are susceptible (sensitive) to oseltamivir and zanamivir.

There is currently no vaccine for this strain, and it will take several months to mass produce one. Depending on the timing of the outbreak this may or may not be in time – but if it is a serious outbreak it will likely last several months, so the vaccine will come out toward the end. The role of the vaccine, therefore, may be to shorten the pandemic, but not to avoid it.

Part of the problem is that flu vaccines are still manufactured with 50 year old technology, using chicken eggs. This is a time consuming process. It will likely take a couple of years to make enough vaccine to inoculate the world against the swine flu. There are companies working on developing newer technologies – where vaccine can be mass produced in vats – but any new technology will not be ready for this pandemic, if it occurs.

The Swine Flu Hubbub

Meanwhile the media has treated the swine flu with near panic. And not just the media – governments and health organizations like the WHO and CDC are stuck between a rock and a hard place. If they overreact to the potential threat then they are accused of being hysterical. The US government and CDC were soundly criticized for sounding the alarm bells in 1976 when that swine flu amounted to nothing. Yet, if they under-react we could be left unprepared for the next major pandemic. Mark Crislip argued, and I agree, it is better to be a little over-prepared than a little under-prepared.

Already the WHO is being criticized for overreacting to this swine flu. In response WHO officials warn that there could be a second wave of swine flu outbreaks in a month or two – which is what happened in 1918. And as I stated above, they are simultaneously being criticized for not reacting fast enough.

Rather than focusing on pointing fingers at this stage of the game, the WHO, CDC, and world governments should simply plan prudently for a pandemic, and then hope to be wrong.

Another aspect of the hysteria is countries fighting with each other. Mexico is getting a little defensive that travel and exports from Mexico may be restricted – so maybe they are downplaying the number and severity of cases to avoid this. Other countries, even old allies, are bickering over recommendations for travel restriction. Concerns have already been raised that the UK might horde their flu vaccines, leaving the US high and dry.

It seems to me that the purpose of an organization like the WHO is to coordinate international information and efforts to avoid this very type of national bickering in times of a world-wide health crisis. Although the media may give the impression of chaos, behind the headlines the recommendations and actions of the CDC and WHO are all reasonable and prudent. I am optimistic that when the next big pandemic hits the WHO, CDC and similar organizations will rise to the task and do what is necessary.The question is – is there anything that can be done to avoid a pandemic, or do we have to ride it out and take steps to minimize it.

And, of course, with swine flu grabbing headlines the quacks and cranks have come out of the woodwork to exploit the situation to push their woo and pseudoscience. Offers for snake oil for the swine flu infected spam last week, accounting for 2% of all spam.

The Huffington Post, rapidly becoming the leader of health pseudoscience on the web, has had several recent posts recommending every sort of dubious health treatments and preventions for the swine flu. Orac at Respectful Insolence does a nice takedown of the swine flu woo over at the HuffPo.

And of course the conspiracy theorists have to have their say as well. They can see the Truth behind the hype that the swine flu was manufactured as part of the latest government dark cabal conspiracy to control the world.


At present there is no cause to panic over the swine flu. Yes – this could be a serious outbreak, but we just have to wait and see. So far the early signs are already indicating this will not be a major pandemic, and may already be on the way out. But we still have to watch closely to see which way it will go. The CDC and WHO will be the best sources of information in the coming weeks. I would avoid the day-to-day roller-coaster of mainstream media headlines and focus on the official reports and recommendations.

The best recommendations are to take simple and rational steps to avoid getting infected, or if symptomatic to avoid spreading the infection to others. This means staying home if you are sick with flu-like symptoms. Wash your hands before and after using public facilities or contact with others who may be infected.

But even if the swine flu of 2009 proves to be like the 1976 fizzle, eventually we will be hit with another pandemic. For every pandemic there are likely to be a dozen false alarms. The public should not be dismayed by these false alarms nor should they lose faith in the CDC and WHO when early warnings do not pan out. Their job is to keep their eye on early outbreaks, knowing most will not amount to a pandemic, but waiting for the one that will.

Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.