Microbiology topic on pathogens, specifically on BSL-4. During our 3rd year high school.

1. Shaina Mavreen D. Villaroza
Microbiology
1. 3 examples of pathogens that are at BSL-4:
a.) Ebola virus (EBOV) causes severe disease in humans and in nonhuman primates in the form
of viral hemorrhagic fever.
Ebola virus was first introduced as a possible new "strain" of Marburg virus in 1977 by
two different research teams. At the same time, a third team introduced the name Ebola
virus. In 2000, the virus name was changed to Zaire Ebola virus and in 2005 to Zaire Ebola
virus.
b.) Smallpox is an infectious disease unique to humans, caused by either of
two virus variants,Variola major and Variola minor. The disease is also known by
the Latin names Variola or Variola vera, which is a derivative of the Latin varius, meaning
"spotted", or varus, meaning "pimple". The term "smallpox" was first used in Europe in the 15th
century to distinguish variola from the "great pox" (syphilis).
Smallpox localizes in small blood vessels of the skin and in the mouth and throat. In
the skin, this results in a characteristic maculopapular rash, and later, raised fluid-
filled blisters. V. major produces a more serious disease and has an overall mortality rate of 30–
35%.
V. minor causes a milder form of disease (also known
as alastrim, cottonpox, milkpox, whitepox, and Cuban itch) which kills about 1% of its victims.
c.) Hantaviruses are negative sense RNA viruses in the Bunyaviridae family. Humans
may be infected with hantaviruses through rodent bites, urine, saliva or contact with rodent
waste products. Some hantaviruses cause potentially fatal diseases in humans, hemorrhagic
fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS), but others have
not been associated with human disease. Human infections of hantaviruses have almost
entirely been linked to human contact with rodent excrement, but recent human-to-human
transmission has been reported with the Andes virus in South America. The name hantavirus is
derived from the Hantan River area inSouth Korea, which provided the founding member of the
group: Hantaan virus (HTNV), isolated in the late 1970s by Ho-Wang Lee and
colleagues. HTNV is one of several hantaviruses that cause HFRS, formerly known as
Korean hemorrhagic fever.
2.) Different Modes of Transimission of Diseases
Droplet Contact

2. Also known as the respiratory route, it is a typical mode of transmission among many infectious
agents. If an infected person coughs or sneezes on another person the microorganisms, suspended in
warm, moist droplets, may enter the body through the nose, mouth or eye surfaces. Diseases that are
commonly spread by coughing or sneezing include
 Bacterial Meningitis
 Chickenpox
 Common cold
Viral Droplet Nuclei Transmission
Droplet nuclei are an important mode of transmission among many infectious viruses such as
Influenza A. When viruses are shed by an infected person through coughing or sneezing into the air, the
mucus coating on the virus starts to evaporate. Once this mucus shell evaporates the remaining viron is
called a droplet nucleus or quanta. The mucus evaporation rate is determined by the temperature and
humidity inside the room. The lower the humidity, the quicker the mucus shell evaporates thus allowing
the droplet nuclei to stay airborne and not drop to the ground. The low indoor humidity levels in
wintertime buildings ensure that higher levels of droplet nuclei will survive: droplet nuclei are so
microscopic that they are able to stay airborne indefinitely on the air currents present within indoor
spaces. The Wells-Riley equation predicts the infection rates of persons who shed quanta within a
building and is used to calculate indoor infection outbreaks within buildings. When an infected person
coughs or sneezes, a percentage of their viruses will become droplet nuclei. If these droplet nuclei gain
access to the eyes, nose or mouth of an uninfected person– either directly, or indirectly after touching a
contaminated surface – then the droplet nuclei may penetrate into the deep recesses of their lungs. Viral
diseases that are commonly spread by coughing or sneezing droplet nuclei include
 Common cold
 Influenza A & B
 Mumps
Fecal-Oral Transmission
Direct contact is rare in this route, for humans at least. More common are the indirect routes; foodstuffs
or water become contaminated and the people who eat and drink them become infected. In developing
countries most sewage is discharged into the environment or on cropland as of 2006; even in developed

3. countries there are periodic system failures resulting in a sanitary sewer overflow. This is the typical
mode of transmission for the infectious agents of :
 Cholera
 Hepatitis A
 Polio
Sexual Transmission
This refers to any disease that can be caught during sexual activity with another person,
including vaginal or anal sex or through oral sex . Transmission is either directly between surfaces in
contact during intercourse or from secretions which carry infectious agents that get into the partner's
blood stream through tiny tears in the penis, vagina or rectum. In this second case, anal sex is
considerably more hazardous since penis opens more tears in the rectum than the vagina, as the
vagina is more elastic and more accommodating.
Some diseases transmissible by the sexual route include
 HIV/AIDS
 Chlamydia
 Genital warts
Oral Transmission
Diseases that are transmitted primarily by oral means may be caught through direct oral contact such
as kissing, or by indirect contact such as by sharing a drinking glass or a cigarette.
 Cytomegalovirus infections
 Herpes simplex virus
 Infectious mononucleosis
Transmission by direct contact
Diseases that can be transmitted by direct contact are called contagious These diseases can also be
transmitted by sharing a towel or items of clothing in close contact with the body if they are not washed

4. thoroughly between uses. For this reason, contagious diseases often break out in schools, where towels
are shared and personal items of clothing accidentally swapped in the changing rooms.
Some diseases that are transmissible by direct contact include:
 Athlete's foot
 Impetigo
 Syphilis
Vertical Transmission
This is from mother to child, often in utero or during childbirth. It occurs more rarely via breast milk.
Infectious diseases that can be transmitted in this way include: HIV, Hepatitis B and Syphilis.
Vector borne transmission
A vector is an organism that does not cause disease itself but that transmits infection by
conveying pathogens from one host to another.
The route of transmission is important to epidemiologists because patterns of contact vary between
different populations and different groups of populations depending on socio-economic, cultural and
other features. For example, low personal and food hygiene due to the lack of a clean water supply may
result in increased transmission of diseases by the fecal-oral route, such as cholera.