Thomas Bergstrom, Sahlgrenska University Hospital
Opening Note: Death due to infectious disease has almost been eliminated in the US since 1900. Unfortunately, this is not so in Sub-Saharan Africa. Today, we will discuss global responses to viral epidemics.
Background
- The eradication of smallpox demonstrates that through global, coordinated efforts, viral epidemics can be eliminated.
o Smallpox is unique in that the symptoms are visible and easily diagnosed.
o Once cases of smallpox were identified, the effected person and/or people were isolated.
o There is no carrier stage in smallpox.
o A vaccine for smallpox was created 200 years ago.
o The creator of the vaccine studied smallpox for 20 years.
o The vaccine was given to French and English soldiers during the Napoleonic Wars.
o Once coordinated, global efforts began, it only took about 10 years to eradicate smallpox.
o Strains of smallpox are still stored in military laboratories and could be redeployed. However, neither smallpox nor any other virus would serve as a good weapon.
- The primary sources of newly emerging infections in humans are animals.
o The West Nile Virus- wild birds/ mosquitoes
o SARS virus- pteropid bats?
o Influenza A virus- wild ducks
o However, humans are equally vulnerable to human infection as evidenced by the spread of measles, HIV, Ebola, etc.
- Emerging diseases have enormous impacts on the following:
o Public health
o Animal health/ welfare
o Food supply
o Economies
o Environment (Biodiversity)
- It is important to note that humans dominate the biological world.
- The recent human population explosion and urbanization have serious implications from the spread of infectious diseases globally.
o Today, people are more exposed to ticks, rats and mosquitoes than ever before.
- Contacts with exotic “pets” also contribute to the spread of infections.
- Emerging virus infections in the last decennia have been facilitated by changes in:
o The social environment including mobility, behavior, demography, socio-economic status and public health measures. (A break-down in public health measures could lead to increased spread of viruses. / How you structure your health-care determines how many people will die from infections.)
o Technology including medical technology and food production.
o Virus mutation and recombination.
o Ecology including animal contacts, agriculture, fisheries, environmental pollution and global warming. (Global warming has led to an exponential proliferation of the mosquito population in the Northern Hemisphere.)
- Nature is the main bioterrorist!
- Humans are also destroying / altering habitat conditions.
Morbilliviruses (measles)
- This air-born virus is a great threat to all species. However, it is important to keep in mind that no infection kills everyone; there are always survivors.
- Seals contracted measles from dogs in Northern Europe.
Coronaviruses (SARS)
- SARS is a new human coronavirus that was big news in 2003.
- SARS is the best example after smallpox of rapid global cooperation in the eradication of a virus.
o Scientific data was shared.
o A steering committee was appointed by the WHO.
o There was rapid implementation of prophylactic measures.
o There was rapid development of diagnostics.
o Thus, the outbreak was terminated in less than 6 months.
- SARS was transmitted to humans in live animal markets in South East Asia.
- SARS was originally a bat virus. Incidentally, bats are a common source of viruses including rabies, Ebola, etc.
Influenza Viruses
- Symptoms of influenza include:
o A fever of more than 39 degrees Celsius
o Acute onset
o Myalgia
o Total malaise
o Shivers
o Coughing
o Redness of mucosa in the nose and throat
- 20th Century influenza pandemics include:
o 1918: “Spanish Flu,” more than 40 million deaths, A(H1N1)
o 1957: “Asian Flu,” 1-4 million deaths, A(H2N2)
o 1968: “Hong Kong Flu,” 1-4 million deaths, A(H3N2)
- Today’s flu pandemic (2009) is characterized by:
o Easy transmission
o Easy mutation
o Exchange between species and genes
o Almost no immunity since those exposed to the Spanish Flu are now dead.
o Younger victims
o Diarrhea which is unusual in the seasonal flu
- The current pandemic is a variant of the Spanish Flu and is neither the Avian Flu nor the Swine Flu.
- The Avian influenza can be transmitted to humans but then cannot be transmitted from human to human.
o There has been no documented spread between humans.
o There have been 442 reported human cases, of which 262 died. This is a 60% mortality rate.
- Is our influenza preparedness good?
o There is constant surveillance by the WHO.
o Culling has and does occur.
o There is strict control over bird markets.
o There are adequate and rapid diagnostics.
o There are levels of public awareness.
- The current flu vaccine targets specific viral strains and has much better average protection.
o Generally, Sweden is against vaccination but Sweden is currently universally recommending vaccination.
Emerging Viruses
- Emerging viruses are being identified with increasing frequency in the human and animal worlds.
- As a result, we should invest in early warning systems and pandemic preparedness plans.
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