Microorganism: rubella virus, which is part of the family Togaviridae

Disease: rubella or German measles

Occurrence of the disease

History: rubella was first described in the 1800s in Germany. An epidemic occurred in the United States in 1964-1965. In the course of this epidemic 30,000 fetuses died and more than 20,000 infants were born with cardiac problems, mental retardation, or visual or hearing defects. Massive vaccination campaigns were started in 1968.

Current situation: 168 cases of rubella were reported in Canada in 1998.

Mechanism of action of the microorganism: the virus multiplies in the respiratory system. It is then able to migrate through the bloodstream or the lymphatic system to the skin.

Symptoms of the disease: small red spots, fever, and eventually discomfort in the joints of the fingers, wrists, and knees.

Infection with rubella in the early stages of pregnancy may have serious consequences for the baby. Congenital malformations may result and the fetus is Read More

Microorganism: rubella virus, which is part of the family Togaviridae

Disease: rubella or German measles

Occurrence of the disease

History: rubella was first described in the 1800s in Germany. An epidemic occurred in the United States in 1964-1965. In the course of this epidemic 30,000 fetuses died and more than 20,000 infants were born with cardiac problems, mental retardation, or visual or hearing defects. Massive vaccination campaigns were started in 1968.

Current situation: 168 cases of rubella were reported in Canada in 1998.

Mechanism of action of the microorganism: the virus multiplies in the respiratory system. It is then able to migrate through the bloodstream or the lymphatic system to the skin.

Symptoms of the disease: small red spots, fever, and eventually discomfort in the joints of the fingers, wrists, and knees.

Infection with rubella in the early stages of pregnancy may have serious consequences for the baby. Congenital malformations may result and the fetus is at risk of dying. All women should check their immunization status against rubella before attempting to become pregnant. In the United States fewer than ten cases of rubella-related congenital malformations are reported per year.

Incubation period: between 12 and 23 days.

Contagious period: the contagious period lasts from one week before to four days after the appearance of the skin rash.

Hosts: humans

Transmission: this is a very contagious disease. The virus is spread in drops of saliva from infected persons.

Treatment: none – rubella is a minor infection.

Geographical distribution of the microorganism: worldwide

Prevention: vaccine

Vaccine: the rubella vaccine is derived from an attenuated virus. This vaccine is combined with the vaccines against measles and mumps in a vaccine called MMR. Children are injected with this vaccine at 12 and 18 months. Ninety-nine per cent of those who have been vaccinated with the recommended doses are protected against rubella.


© Robert Alain, SME, INRS-Institut Armand-Frappier

Rubella virus

Photo : Robert Alain

© Robert Alain, SME, INRS-Institut Armand-Frappier


Microorganism: variola virus, a member of the Poxviridae family

Disease: smallpox

Occurrence of the disease

History: in the process of colonizing the Americas, Europeans brought with them many diseases unknown to the aborigines, including smallpox. At that period, smallpox was one of the most widespread diseases in Europe, and Europeans had developed some degree of resistance to it. Aborigines, on the other hand, had no resistance to the disease and were devastated by its introduction in the New World. In 1966, the World Health Organization (WHO) undertook a worldwide vaccination campaign that succeeded in eradicating the disease eleven years later in 1977. Nevertheless, a laboratory accident caused the death of one person in 1978.

Current situation: the smallpox virus now exists only in a few laboratories around the world where it is kept for research purposes.

Forecast: the destruction of the last colonies of variola virus is planned for the year 2002.

Symptoms of the disease: small Read More

Microorganism: variola virus, a member of the Poxviridae family

Disease: smallpox

Occurrence of the disease

History: in the process of colonizing the Americas, Europeans brought with them many diseases unknown to the aborigines, including smallpox. At that period, smallpox was one of the most widespread diseases in Europe, and Europeans had developed some degree of resistance to it. Aborigines, on the other hand, had no resistance to the disease and were devastated by its introduction in the New World. In 1966, the World Health Organization (WHO) undertook a worldwide vaccination campaign that succeeded in eradicating the disease eleven years later in 1977. Nevertheless, a laboratory accident caused the death of one person in 1978.

Current situation: the smallpox virus now exists only in a few laboratories around the world where it is kept for research purposes.

Forecast: the destruction of the last colonies of variola virus is planned for the year 2002.

Symptoms of the disease: smallpox is a viral disease that causes a severe skin rash in the form of pustules. Other symptoms may occur, such as fever, headache, back pain, and occasionally abdominal pain and vomiting.

There are two types of smallpox: variola minor and variola major. Variola minor has a mortality rate of less than one per cent; that of variola major is 20 to 40%, or more.

Incubation period: the incubation period varies between seven and 19 days.

Contagious period: the contagious period starts with the first lesions and lasts until the disappearance of the last scabs (about three weeks).

Transmission: person to person through ambient air

Hosts: humans are the only host for this disease. Today, the last colonies are stored in freezers under high security.

Geographical distribution of the microorganism: this organism used to be found worldwide. However, no case of smallpox has been reported since 1977.

Vaccine: Jenner developed a vaccine against smallpox in 1798. Mass immunization with the cowpox virus (a similar virus occurring among cattle, but not infectious to humans) has permitted the eradication of smallpox.


© Armand-Frappier Museum, 2008. All rights reserved.

Variola virus

Photo : Robert Alain

© Robert Alain, SME, INRS-Institut Armand-Frappier


Microorganism: the human papillomavirus (HPV), family: Papovaviridae.

Disease: warts

Occurrence of the disease

Mechanism of action of the disease: the virus attacks the skin, and spreads by direct contact.

Symptoms of the disease: skin lesions (warts).

Incubation period: two to three months, on average.

Contagious period: unknown, but probably as long as the lesions are present.

Hosts: humans.

Transmission: usually by direct contact. Scratching may result in self-inoculation, i.e., propagation of the warts from one part of the body to another.

Treatment of the disease: warts usually disappear on their own within a few months or years, but may be removed with liquid nitrogen, lasers, or the direct application of podophyllum, a drug.

Geographical distribution of the microorganism: worldwide.

Prevention: avoidance of contact with infected individuals.

Read More

Microorganism: the human papillomavirus (HPV), family: Papovaviridae.

Disease: warts

Occurrence of the disease

Mechanism of action of the disease: the virus attacks the skin, and spreads by direct contact.

Symptoms of the disease: skin lesions (warts).

Incubation period: two to three months, on average.

Contagious period: unknown, but probably as long as the lesions are present.

Hosts: humans.

Transmission: usually by direct contact. Scratching may result in self-inoculation, i.e., propagation of the warts from one part of the body to another.

Treatment of the disease: warts usually disappear on their own within a few months or years, but may be removed with liquid nitrogen, lasers, or the direct application of podophyllum, a drug.

Geographical distribution of the microorganism: worldwide.

Prevention: avoidance of contact with infected individuals.

Vaccine: none.


© Armand-Frappier Museum, 2008. All rights reserved.

Human papillomavirus

Photo : Robert Alain

© Robert Alain, SME, INRS-Institut Armand-Frappier


Microorganism: West Nile virus, family: Flaviviridae.

Disease: West Nile fever

Occurrence of the disease

History: the West Nile fever virus was isolated in 1937 in a woman in the West Nile district of Uganda.

Some specialists believe the West Nile virus to have been brought to North America by migrating birds. However, because most birds do not cross the Atlantic Ocean, others believe the virus to have come to North America via imported birds or infected humans.

Current situation: the first cases of West Nile fever in the western hemisphere were reported in 1999 in the state of New York. The epidemic affected 61 people and resulted in seven deaths. Birds and horses were also affected.

Mechanism of action of the microorganism: the virus enters the body through a mosquito bite and infects a variety of tissues. In severe cases, it may attack nerve cells. No cases of West Nile fever have been reported in Canada.

Symptoms of the disease: fever, headache, sore throat, back pain, fati Read More

Microorganism: West Nile virus, family: Flaviviridae.

Disease: West Nile fever

Occurrence of the disease

History: the West Nile fever virus was isolated in 1937 in a woman in the West Nile district of Uganda.

Some specialists believe the West Nile virus to have been brought to North America by migrating birds. However, because most birds do not cross the Atlantic Ocean, others believe the virus to have come to North America via imported birds or infected humans.

Current situation: the first cases of West Nile fever in the western hemisphere were reported in 1999 in the state of New York. The epidemic affected 61 people and resulted in seven deaths. Birds and horses were also affected.

Mechanism of action of the microorganism: the virus enters the body through a mosquito bite and infects a variety of tissues. In severe cases, it may attack nerve cells. No cases of West Nile fever have been reported in Canada.

Symptoms of the disease: fever, headache, sore throat, back pain, fatigue, nausea, weight loss, stomach pain, diarrhea and breathing problems. In half the cases, infected individuals also have small pink skin eruptions. The virus may also cause severe encephalitis (inflammation of the brain). The disease is most severe in older women and in immunodeficient individuals.

Incubation period: unknown. Five to 11 days for Japanese encephalitis, a disease similar to West Nile fever.

Contagious period: West Nile fever is usually not transmitted between humans.

Hosts: some birds and mosquitoes.

Transmission: the West Nile fever virus is transmitted from birds to humans by mosquitoes, primarily those of the genus Culex.

Geographical distribution of the microorganism: Africa, Europe, the Middle East, central and west Asia, Oceania, and more recently, North America.

Prevention: control of mosquitoes is the most effective means of preventing transmission of the disease.

Vaccine: none.

West Nile fever resembles other diseases such as Japanese encephalitis and St. Louis encephalitis, and all three diseases are caused by members of the Flaviviridae family. A Japanese encephalitis vaccine, consisting of inactivated viruses obtained from mouse brain, is available.


© Armand-Frappier Museum, 2008. All rights reserved.

West Nile fever

Illustration by Bruno Laporte

© Illustration by Bruno Laporte


Microorganism: the virus responsible for yellow fever is a flavivirus belonging to the family Flaviviridae.

Disease: yellow fever

Occurrence of the disease

History: yellow fever was the first human disease attributed to a virus. Large epidemics affected tropical America in the 17th, 18th and 19th centuries making it the "most feared disease of the Americas."

Current situation: between 1986 and 1991, 20,000 cases were reported in Nigeria, including 4,000 deaths. Since 1942, there have been no urban yellow fever epidemics due to the mosquito A. aegypti in America.

Forecast: many cities in America suffer from a re-infestation of the mosquito A. aegypti, which could possibly result in an epidemic. However, in 1998, no cases were reported in Canada.

Mechanism of action of the microorganism: this virus is capable of reproducing inside many different tissues of the Aedes aegypti mosquito (commonly called the Asian tiger mo Read More

Microorganism: the virus responsible for yellow fever is a flavivirus belonging to the family Flaviviridae.

Disease: yellow fever

Occurrence of the disease

History: yellow fever was the first human disease attributed to a virus. Large epidemics affected tropical America in the 17th, 18th and 19th centuries making it the "most feared disease of the Americas."

Current situation: between 1986 and 1991, 20,000 cases were reported in Nigeria, including 4,000 deaths. Since 1942, there have been no urban yellow fever epidemics due to the mosquito A. aegypti in America.

Forecast: many cities in America suffer from a re-infestation of the mosquito A. aegypti, which could possibly result in an epidemic. However, in 1998, no cases were reported in Canada.

Mechanism of action of the microorganism: this virus is capable of reproducing inside many different tissues of the Aedes aegypti mosquito (commonly called the Asian tiger mosquito) as well as in human or monkey tissues. The virus travels to the lymph nodes, then moves on to the liver, the spleen, the kidneys, and the heart.

Symptoms of the disease: fever, muscular pain, nausea, vomiting. Jaundice may also appear, moderate at the beginning of the disease and more severe towards the end. Fever and jaundice have given the disease its name. The majority of cases reach this point and then recovery follows. In certain cases, however, a kidney lesion develops that can be fatal.

Geographical distribution of the microorganism: the majority of the tropical countries of Central and South America, as well as Africa.

Incubation period: about three to six days

Contagious period: human blood can infect mosquitoes shortly before the appearance of fever and during the first three to five days of the disease. Then follows an incubation period of nine to 12 days in the mosquito, after which the mosquito is contagious for the rest of its life.

Transmission: the disease is transmitted by a mosquito called Aedes aegypti. There are two cycles of transmission: the urban cycle (epidemic) and the jungle cycle. In the urban cycle, the virus spreads from person to person by mosquito bites. The blood of an infected patient contains the virus. When the mosquito bites a human, it ingests virus along with the blood. The virus then travels to the intestinal tissues of the insect, reproduces and then moves to the salivary glands of the mosquito. By biting other humans, the insect injects them with the virus. The jungle cycle works essentially in the same way, except that the insects bite wild animals such as monkeys instead of humans.

Hosts: humans, monkeys, and mosquitoes

Discoverer of the microorganism: Walter Reed in 1901

Treatment: no treatment exists for this disease

Geographical distribution of the microorganism: The virus is found especially in Central and South America, and in Africa.

Prevention: vaccine

Vaccine: the vaccine used is in fact the attenuated virus. It is effective in 99% of cases. Immunization persists in the body for about 35 to 40 years but a booster is suggested for people travelling to high-risk locations.

Vaccination is often required to enter endemic zones. Although yellow fever is widespread in South America and in Africa, it has never reached Asia, even though Asians also get bitten by A. aegypti. The reason for this phenomenon is unknown.


© Armand-Frappier Museum, 2008. All rights reserved.

Virus responsible for yellow fever

CDC

© CDC


Learning Objectives

The learner will:
  • familiarize himself with the vocabulary used in microbiology;
  • explain the relationship between developments in imaging technology and the current understanding of the cell;
  • identify which microorganisms are infectious, how the immune system fights against them, and the reinforcements of modern medicine;
  • describe the benefits of microorganisms.

Teachers' Centre Home Page | Find Learning Resources & Lesson Plans