Temporary is not a term applied to viral infections.
Correct Answer: Temporary
Acute infections involve the rapid production of virions followed by rapid resolution and elimination of the infection by host defenses. Two excellent examples of this type of infection are influenza (caused by influenza virus) and the common cold (caused by rhinovirus).
Correct Answer: Rapid production of virus and rapid resolution of infection by host defence
Influenza has an incubation period of 1 to 2 days.
Correct Answer: Influenza
Mumps has an incubation period of 17 to 20 days.
Correct Answer: Mumps
Papilloma virus has an incubation period of 2 to 3 months.
Correct Answer: Papilloma
HIV has the longest incubation period of 1 to 10 years.
Correct Answer: HIV
Antigenic shift describes major changes in the structure of the virion as a result of the acquisition of new genes either from co-infection or through recombination events.
Correct Answer: Antigenic shift
Latent infections have three general characteristics: absence of an early productive infection (in other words, no large-scale production of virions), reduced or absent host immune response, and persistence of an intact viral genome so that productive infections. They can also integrate into the host chromosome.
Correct Answer: The presence of an early productive infection
In a latent infection, the viral genome integrates into the host chromosome (without destroying it) and remains there until it is re-activated. The age of the host doesn’t affect the type of infection.
Correct Answer: Can integrate into the host chromosome
Virulence varies from one virus to another and can be directly affected by the route of infection and by the age, the health, and in some cases the gender of the host. Alterations in the ability of the virus to replicate can also affect virulence, for example, a genetic mutation that decreases the number of virions produced in an infected host cell can lower the virulence of the virus. Last, any change in a host cell’s function can affect virulence.
Correct Answer: All of the choices
Although the digestive tract is a common route of infection, it is extremely hard on the virus because of the hostility of the environment, which contains stomach acid, bile, strong digestive enzymes, immunoglobulins, and phagocytic cells. Consequently, viruses that infect the digestive tract must be resistant and resilient.
Viruses that are released from the basal surface of the host cell are released into the underlying tissues and usually spread to other sites.
Correct Answer: Cause a systemic infection
Iatrogenic transmission is transmission of infection because of poor techniques employed by health care workers.
Correct Answer: Health care workers
Like many viruses, rabies virus uses the neuronal network to disseminate through a host’s body. For rabies virus, the neuron is also the target. In rabies, for instance, both mature virions and nucleocapsids have been identified in the axons and dendrites of neurons.
Correct Answer: The neuron
Hepatitis C virus can spend years travelling round in the blood stream and targets hepatocyte cells in the liver, where it can cause a persistent infection leading to serious liver damage. It is transmitted by contact with infected blood.
Correct Answer: Can spend years traveling round the blood
Virulent virus is never used in a vaccine because it may produce disease in healthy people and spread the disease.
Correct Answer: Non-virulent and attenuated virus
The PD50 (paralytic dose 50%), indicates how much virus is needed to paralyze 50% of infected individuals. Although all this measurement may seem to be somewhat arbitrary, it is an important indicator of the potential virulence of some viruses.
Correct Answer: Paralytic dose of a virus in 50% of infected individuals
Koplik’s spots are white pus pimples seen on the oral mucosa several days before the outbreak of the measles rash.
Correct Answer: Measles
In 1796 (more than 200 years ago) Edward Jenner developed a vaccine for smallpox. First polio vaccines became available in 1918 and reached millions in the 1950s. Measles, Mumps and Rubella vaccine appeared in the 1960s.
Correct Answer: Smallpox
A live attenuated vaccine is made up of intact viral particles that have been mutated and selected for based on their poor growth in humans. Because these vaccines are composed of infectious virions, there is the potential danger of accidental infection of individuals receiving the vaccination.
Correct Answer: Consists of live attenuated virus
Only inactivated vaccines are made from dead pathogens: live attenuated vaccine is made up of intact viral particles that have been mutated and selected for based on their poor growth in humans, subunit vaccines are composed of immunogenic parts of the virus.
Correct Answer: The vaccine must be made from killed pathogens
Oncogenic viruses are viruses of any family that are associated with the development of cancer. They cause persistent infections and it seems that viral proteins or transcriptional controls override the mechanisms that normally ensure that cells divide only when necessary. Such overriding leads to the uncontrolled cell growth that we know by the generic term cancer.
Correct Answer: Are associated with cancers
Norwalk virus uses the gastrointestinal tract as its portal of entry, where it first enters specialized cells called M cells. From these M cells it can enter lymphocytes and be disseminated throughout the body.
Correct Answer: M cells
The cold sore is a symptom of the herpes simplex virus.
Correct Answer: Herpes simplex virus
The MMR vaccine is a type of live attenuated vaccine.
Correct Answer: MMR
A live attenuated vaccine is made up of intact viral particles that have been mutated and selected for based on their poor growth in humans.
Correct Answer: A vaccine with intact viral particles
An inactivated vaccine, also called a killed vaccine, is composed of virus that is either dead or made non-infectious via chemical or physical treatment.
Correct Answer: A vaccine with either dead or non-infectious particles
A subunit vaccine is composed of immunogenic parts of the virus and is usually made using genetic engineering and recombinant DNA techniques.
Correct Answer: A vaccine of viral immunogenic parts
Edward Jenner infected a boy with the harmless (to humans) cowpox virus and then infected him with smallpox. The boy didn’t become ill.
Correct Answer: The use of harmless virus as vaccine