Smallpox – or how I learned to love child endangerment

I’ve been on a conference, so I haven’t had time to write a new article this week. Instead, you get sloppy seconds this week. This article was previously published in On Dit (2006) as my first public article. Still carries on the  series though. Oh, and happy birthday, Disease of the Week!

ResearchBlogging.org

Smallpox is a now-eradicated disease that is caused by the variola virus. There are two main types of small pox: variola major, the typical case of smallpox that killed up to 30% of those infected with it; and variola minor, which was a less deadly, but rarer form, leading to deaths in around 1% of those infected. Two extremely rare forms also existed: haemorrhagic and flat smallpox, both of which are basically death sentences. Variola major is the primary focus of my story today.

 

Eradication through vaccination is possible, as the case of smallpox has shown (Photo by the American Federal Government via the Public Health Images Library (PHIL))

 

Smallpox is usually spread through breathing in cough or sneeze droplets, but can also be spread, as Native Americans found out, by Thanksgiving blankets or clothes. The pus filled sores also contain large amounts of the virus.

After infection, a person may feel fine for 1.5 to 2 weeks. This is the incubation period, in which time the virus has infected and is replicating in the host’s cells. The virus can’t be transmitted at this time. Flu-like symptoms suddenly erupt and stick around two to three days.

After this, the patient feeld better as a distinctive rash spreads, starting on the face and extremities then progressing to the trunk of the body. Sores forming in the mouth and nose leak newly-replicated virus particles into saliva and mucus, allowing spread through coughing and sneezing. This marks the  start of the infectious phase.

The rash eventually turn into vesicles (small blisters), which then fill with pus. These dry out and turn into scabs. The patient remains infectious until the last of the scabs are shed. Small, pocked scars form, giving the disease its name.

The specific cause of death is still controversial among scientists . Some say that tissue damage due to excessive immune response against the virus is probably what kills people; others say that smallpox leaves the gate open for deadly secondary bacterial infections. What is settled upon is that 30% of all people infected with smallpox died.

Treatment of smallpox involves getting the patient comfortable, waiting around and building a third of a coffin.  Prevention lies in vaccination, which provides a nice segue into the next segment.

As mentioned in previous articles, vaccinations work by inducing antibody production by the immune system. Antibodies are highly specific molecules that recognise a particular shape of a molecule and attach to it. Antibodies specific to viruses (such as smallpox) stick to them and make it easier for the immune system to destroy. The mechanism is like the exploding ink packets marking a bank robber.

Before exposure to the virus, there are very few antibodies specific to smallpox produced because antibodies take energy to make. The body has to have a small level of antibodies specific to all of the different things you might encounter, so only a few of each type can be made. To extend the analogy, only one or two of the bags of money in the bank have ink packets in them because they cost too much.

Once a patient is exposed, the antibody binds to the virus. This binding is detected by the immune system, which responds by pumping out some more of the same type. The police see that the ink packet has exploded, and realise there’s a crimewave. They go pick up some more ink packets from the shop to mark more robbers.

A virus can become deadly if it replicates quickly before the immune system can produce enough antibodies to neutralise them. The bank goes bankrupt before the cops come back from the shop.

By vaccinating, we’re telling the immune system to produce more antibodies toward a virus by giving them a slow, dumb target to train against. So after vaccination, there are lots of antibodies specific to smallpox around – i.e., there are plenty of ink packets around to tag robbers. So even if a large group of quick robbers come, they can all be tagged and quickly arrested.

 

Development of the smallpox vaccine (Photo by CDC)

 

The vaccine for smallpox was a great invention and eventually led to the eradication of the disease, saving untold millions from a horrible death. In 1796, science (in the form of Edward Jenner, a milkmaid and a young boy) would start wiping out the disease that killed 300 million people in the 20th century alone and countless more before it.

Before this time, doctors were emplying person suffering from variola minor. They took a pustule from this patient and vaccinated people with the pus. This way they would only get a mild case, but would have built up antibodies to battle any upcoming variola attacks. This technique had its downsides: you didn’t have people with variola minor everywhere, you still ran a chance of dying from variola minor and it spread smallpox throughout the population.

Enter Edward Jenner, a doctor during these times. He found that some people he jabbed didn’t end up showing symptoms of the milder form of smallpox, instead they just got a bit red at the site of inoculation and got better. A lot of these people he noticed were sexy milkmaids. The reason why they were sexy was they didn’t have the ugly scars of smallpox on their face and hands.

Jenner eventually found a relationship between the people resistant to the inoculation and previous exposure to cowpox, which is caused by a very similar virus called vaccinia (coming from Latin vacca meaning cow).

Being a scientist, he needed to test his claim. So in 1796, he found a milkmaid with fresh cowpox pustules and removed her pus. He then obtained consent from the parents of an eight year old child, scratched his arms and smeared the pus into them. The boy got cowpox a week later and easily recovered (cowpox doesn’t kill healthy people). Now for the real test; Jenner took pus from a smallpox-infected man and jabbed the boy with it. Nothing happened. So he jabbed him again and again. And again and again and again. He was immune to the smallpox virus!

He repeated this with 13 other people with great results. So much so, he published his findings in a small book he paid for out of his own pocket. People doubted him, as people often do with new things, but after a while it was popularised by other doctors. The news of vaccinia (which incidentally is where we get the word vaccine) spread around the world. By 1980, the world saw its last case of smallpox and the World Health Organisation declared it eradicated.

 

Making sure this doesn't happen again - A Bangladeshi girl with smallpox 4 years before eradication (Photo from the CDC and PHIL)

 

As a final point, two small batches of the smallpox virus still exist (one in the former USSR, one in the USA) and are under very strict lock and key. There are people who say we should destroy them while we can and others that say we can gain some good research that could cure other diseases using it. Others think we’re just tempting a bioterrorism incident by leaving it around. What do you think?

Add to FacebookAdd to DiggAdd to Del.icio.usAdd to StumbleuponAdd to RedditAdd to BlinklistAdd to TwitterAdd to TechnoratiAdd to Yahoo BuzzAdd to Newsvine

TT

 

Reference

Stanford, M., McFadden, G., Karupiah, G., & Chaudhri, G. (2007). Immunopathogenesis of poxvirus infections: forecasting the impending storm Immunology and Cell Biology, 85 (2), 93-102 DOI: 10.1038/sj.icb.7100033

Advertisements

7 Comments

Filed under Thomas' Corner

7 responses to “Smallpox – or how I learned to love child endangerment

  1. Pingback: Vaccine styles for specific diseases « Disease of the Week!

  2. Pingback: Viruses Vs. Bacteria – Debate Rebuttals « Disease of the Week!

  3. Pingback: De verborum notatio morbi – On the etymology of diseases « Disease of the Week!

  4. Pingback: Syphilis – or how love drives people crazy « Disease of the Week!

  5. Pingback: Scientia Pro Publica 43: Loving, Living, Learning « Traversing the Razor

  6. Pingback: Blogging Carnival Selection! « Disease of the Week!

  7. Pingback: Quick Links | A Blog Around The Clock

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s