Zoom in on microorganisms

Germs that infect humans



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

Microorganism: this virus is a member of the genus Morbillivirus of the family Paramyxoviridae.

Disease: measles

Occurrence of the disease

History: following the launch of a widespread vaccination program in 1966, the number of cases of measles has decreased by 98%.

Current situation: between 2,000 and 3,000 cases of measles are reported each year in the United States. However, 90% of these occur in non-vaccinated people. In the developing countries without vaccination programs, 220,000 deaths from measles occur each year. In 1994 the industrialized countries undertook to eradicate the spread of measles by the end of the year 2005. In Canada only 16 cases of measles were reported in 1998.

Mechanism of action of the microorganism: the measles virus enters the organism via the respiratory system or the ocular conjunctiva (eyes) and multiplies within the cells in the lung. From there it enters the bloodstream and travels to different organs, including the skin.

Symptoms of the disease: the first signs of the disease are nasal secretions, fever, cough, headaches, and conjunctivitis. These are followed by eruptions of the skin, rash and eruptions of the mucous membranes in the mouth. These spots in the mouth, which are red with a blue and white center, are called Koplik’s spots.

Incubation period: ten to 14 days

Contagious period: the contagious period lasts from four days before until four days after the appearance of the rash.

Hosts: humans

Tranmission: this is a very contagious disease.

Treatment: no specific treatment

Geographical distribution of the microorganism: before immunization, measles was present throughout the world. Massive immunization programs have considerably reduced the rate of measles infection in industrialized countries.

Prevention: vaccine

Vaccine: the vaccine against measles is attenuated. This vaccine is combined with vaccines against rubella and mumps. This vaccine is called MMR and the injections are recommended at 12 and 18 months. Ninety-nine per cent of those vaccinated with the two recommended doses are protected against measles.