— Nucleosidic (or nucleotidic) reverse transcriptase inhibitors (NRTI) (for example: azidothymidine, AZT; lamivudine, 3TC; didanosine, ddI, etc.). These are nucleoside analogs that bind to the active center of the enzyme are integrated in the DNA strands, resulting in "chain termination."
— Nonnucleosidic reverse transcriptase inhibitors (NNRTI) (for example: efavirenz, EFV; nevirapine, NVP, etc.). This class of substances also inhibits the production of viral cDNA by reverse transcriptase, but does not prevent viral production by infected cells.
— Protease inhibitors (PI) (for example: indinavir, IDV; ritonavir, RTV; saquinavir, SQV, etc.): PIs inhibit viral protease and thus viral maturation.
Combination Treatments of HIV Infections:
To avoid development of resistant HIV variants, a combination of at least three drugs from at least two substance classes is usually administered. The following combinations are currently established practice:
a) One PI and two NRTIs b) One NNRTI and two NRTIs c) Two PIs and one or two NRTIs d) One PI and one NNRTI, alternatively with one or two NRTIs as well;
e) Three NRTIs a) and b) appear to produce the best long-term results.
Standard vaccines can be used to prevent other infections, for example opportunistic infections in HIV-positive persons, especially children showing no symptoms. The dead vaccine type is recommended for polio. Live vaccine materials should generally not be used in persons showing AIDS symptoms.
Precautions for Healthcare Staff ■
All personnel in medical professions should know that HIV is not highly contagious and that precautions, as they apply to hepatitis B, are considered sufficient: wear protective gloves in all situations involving possible contact with blood. If blood droplets could be spattered or sprayed, masks and goggles should also be worn.
If exposure has occurred despite precautions (accidental injection, stab wound, contamination of a wound or mucosa with material containing HIV), immediate commencement of a combination therapy with one PI and two NRTIs for two to four weeks is indicated in addition to a thorough wound toilet and disinfection.
Viruses with Double-Stranded RNA Genomes Reoviruses
■ Reoviruses possess a segmented, double-stranded RNA genome. Among the reoviruses, the rotaviruses are the most significant human pathogens. They cause diarrhea in small children and the elderly and can also produce severe sequelae in immunosuppressed patients.
Diagnosis: reovirus—isolation; rotavirus—antigen detection or electron microscopy. Isolation of this viral type in cell cultures is not a routine method. ■
Pathogen. The name reovirus is derived from the abbreviation for respiratory enteric orphan virus, recalling that no diseases were associated with the virus upon its discovery (hence "orphan virus"). The family Reoviridae includes, in addition to phytopathogenic and zoopathogenic strains, three genera in which human pathogens are classified:
— Coltiviruses include a large number of pathogens significant in veterinary medicine as well as the human pathogen virus that causes Colorado tick fever.
— Reoviruses in the narrower sense, with three serogroups.
— Rotaviruses, groups A to F, further subdivided into subgroups, serotypes, and electropherotypes (see below). The rotaviral genome consists of eleven segments of double-stranded RNA. Each segment codes for one viral protein. Some segments in other reoviruses code for two or three proteins.
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