Lecture 7: Biological Hazards and Human Health
• Nontransmissible (cannot be transferred from human to human). Examples of such
nontransmissible diseases include:
-cardiovascular - diseases related to heart as a result of food (high cholesterol), lack of
exercise, lots of stress, smoking, etc
-cancer - many different causes (we cannot specify just one cause for it). Every cancer is
caused with many different agents (environmental, genetical, etc.). No proof that these
diseases can be transferred from human to human
-diabetes - caused because of genetics, food, and obesity. No proof that diabetes can be
transferred from human to human
-asthma - closely related with some allergens (something in our environment). No proof that
asthma can be transmitted from human to human
• Transmissible diseases: (can be transferred from humans to humans). Examples of such
transmissible diseases include: bacteria, viruses, protozoa.
• Bacteria can be cured using anti-biotics.
• However, anti-biotics do not work with viral infections. For example, doctors will not
prescribe anti-biotics if you have flu, or some other kind of viral infection because it can lead
to very significant resistance of bacteria to these anti-biotics.
• This is because growing germ produces resistance to antibiotics. They are growing very fast;
hence quickly transfer that mutation (adjustment) to the next generation. (High reproductive
rate allow them to become genetically resistant quickly).
• One more reason why bacterias grow resistance to anti-biotics is because of the use of
antibiotics in food additives to boost livestock. If we consume that kind of meat (with high
concentration of anti-biotics), we might become more resistant to antibiotics.
• Bacterial Diseases – Tuberculosis, Anthrax, Brucellosis, Various forms of plague
• Viruses – HIV, SARS, Bird Flu, Smallpox, West Nile Virus
• Significant threat in the past (during WWII) and even now.
• Evidence that mummies from Egyptian era had symptoms of tuberculosis.
• This disease used to run in families, as it was transferred from one family member to another
member of the family, very easily. Marriage sometimes depended on if the bride/groom’s
family had tuberculosis.
• During 18 and 19 centuries, this disease was related to vampires because those who had it
were very pale, had watery bloody eyes, and sometimes spit blood
• After discovery of antibiotics, most cases (not all) of tuberculosis were cured.
• Makes it hard to cure because agents (disease) mutate easily and change very quickly. This
can cause different types of tuberculosis (which is why they are a threat today)
• In 2004, mortality statistics included
-14.6 million chronic active TB cases
-8.9 million new cases
-1.6 million deaths (mostly in developing countries) • Chronic active means when an individual comes in contact with an agent (bacteria), that
person does not get ill right away. Active means visible symptoms. Chronic means for a long
• Why is it mostly in developing countries? Disease is a socially related disease. Poor people
with not adequate supply of food, bad housing, wet walls, unsafe conditions, these get sick
more easily because their immune system is reduced (lower) and they catch this disease
faster. Also, their health system is not very organized, not all people have access to proper
health. This adds to one of the reasons for tuberculosis.
• Transmission through - cough, sneeze, speak, kiss, or spit of ill person, breathing (basically,
any direct contact).
• Most commonly attacks the lungs (through the breathing of the agent).
• Sensitive to UV radiation and oxygen
• Symptoms include chest pain, coughing up blood, and a productive, prolonged cough for
more than three weeks, fever, chills, night sweats, appetite loss, weight loss, paleness and
often a tendency to fatigue very easily.
Tuberculosis- a growing threat
• Problem in Africa (mostly southern Africa), South America, Asia. Not a problem in North
America, Australia. If you want to travel in tuberculosis affected countries, you have to get a
• After 9/11 this disease was of big concerns that it can be used as a biological weapon.
• Spores of anthrax (form of bacteria) are usually found in soil. When bacteria is in unpleasant
(something that does not support growth of the bacteria), they become this form to survive,
until they are back in conditions that will be good for them to grow.
• Bacillus anthracis (large gram-positive, spore-forming bacteria).
• Gram test is used by microbiologists to test bacterias. These bacterias produce toxins. This
toxin is really poisonous.
• Three major clinical forms of this disease are seen in the literature:
-Cutaneous, Inhalation, Gastrointestinal.
• All three may lead to septicaemia (large amounts of bacteria that will lead to very serious
conditions and even death)
• No smell or taste. They are so small that they cannot be seen by naked eye.
• Cannot be transmitted from person to person.
• The most common naturally occurring type of anthrax.
• More that 95% of all cases of anthrax are cutaneous.
• Can be contaminated after skin contact with contaminated meat, wool, or leather from
infected animals, or contact with an animal that was sick with anthrax.
• The incubation period ranges from 1-12 days. During this period there are no symptoms.
• After the first 12 days, first symptoms are tiny rash first starting as a bump (like a spider bite,
very tiny). Then it will progress into very severe change in the skin (like pimples). Then it
progresses into vesicle and then a painless ulcer.
• Besides changes in the skin, the person goes through fever, headache, lymph glands swell.
This disease is successfully treated with antibiotics if the treatment starts early
• 20% of all cases not treated or not treated in time will result in death. Inhalation Anthrax
• Inhalation anthrax is the most lethal form.
• Person gets sick through inhalation of spores of anthrax
• The kind of disease that government believes to be a possible bio-weapon.
• Incubation period 1-60 days. Usually the literature says that the range is from 1 – 7 days, but
it can be expanded to 1 – 60 days.
• Starts as viral respiratory illness: sore throat, mild fever, muscle aches, flu.
• May progress to respiratory failure (difficulty breathing and then the person cannot breathe at
all) and shock (losing conscience) with developing meningitis (inflammation of the brain or
membranes around the brain)
• 75 % of cases result in death even with all possible supportive care
• Person gets sick by consumption of raw or uncooked contaminated meat.
• Incubational period (period when there is no symptoms) is 1-7 days.
• Symptoms include nausea, loss of appetite, vomiting, and fever, stomach problems.
• Once they get more severe these symptoms are followed by abdominal pain, vomiting blood
and bloody diarrhoea.
• 25%-60% of cases result in death (not known how effect of early treatment can help)
Bioterrorism Related Anthrax
• Inhalation anthrax is subject of biggest concern that it can be used as a bio-weapon.
• How is it possible? Given that spores are not visible, however, they can be mixed with
powder. This is how the spores can be transported through mail envelopes
• There were a couple of incidents in US that certain government institutions received
suspicious mails (i.e. inappropriate or unusual labelling, excessive postage, no return address,
no x-ray, oily stains, excessive weight)
• What should people do who get a letter with powder? Do not shake, touch, sniff, taste, empty,
and carry the envelope. Put the envelope down on a stable surface, alert others, leave