Published on February 27, 2014
An easy way to catch most infectious diseases is by coming in contact with a person or animal who has the infection. Three ways infectious diseases can be spread through direct contact are:
The most common way for infectious diseases to spread is through the direct transfer of bacteria, viruses or other germs from one person to another.
Pets can carry many germs , Being bitten or scratched by an infected animal can make you sick and, in extreme circumstances, can be fatal.
A pregnant woman may pass germs that cause infectious diseases to her unborn baby. Some germs can pass through the placenta.
AIDS (Acquired immune deficiency syndrome) Caused by human immunodeficiency virus (HIV), a lentivirus within the family Retroviridae It was believed that it have evolved in Africa from viruses that infect other primates This Disease occurs worldwide, but certain groups are more at risk Homosexual/bisexual men Intravenous drug users Transfusion patients Newborn children of infected mothers
This Virus is acquired by direct exposure of the person’s bloodstream to body fluids Containing the virus; can also be transmitted via breast milk Virus targets CD4+ cells such as cells, macrophages, dendritic cells, and monocytes Four types of pathological changes AIDS-related complex (ARC) T-helper mild fever, weight loss, lymph node enlargement, and presence of antibodies to HIV; can develop to full-blown AIDS
Caused by herpes simplex type 1 (HSV-1), a dsDNA virus Transmission is by direct contact Blister at site of infection is due to viraland host-mediated tissue destruction Lifetime latency is established when virus migrates to trigeminal nerve ganglion
70-90% of U.S. adults have been infected Virus is periodically reactivated in times of physical or emotional stress Herpetic keratitis - recurring infections of the cornea that can result in blindness Drugs are available that are effective against cold sores, but treatment is mostly supportive Diagnosed by cell culture and immunological tests
Caused by many different rhinoviruses as well as other viruses Many do not confer durable immunity Understanding rhinovirus structure has suggested approaches to developing vaccines and drugs. At one time, common cold was thought to be spread by explosive sneezing, but now it is believed to be primarily spread by hand-to-hand contact Treatment is supportive
Certain leukemias (adult T-cell leukemia and hairy-cell leukemia) are caused by retroviruses (HTLV-1 and HTLV-2, respectively) and are spread similarly to AIDS Often fatal and there is no effective treatment, although interferon has shown some promise to cure the disease.
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Caused by a number of different strains of neurotropic viruses of the family Rhabdoviridae (negative-strand RNA viruses) Transmitted by bites of infected animals, aerosols in caves where bats roost, or by scratches, abrasions, open wounds, or mucous membranes contaminated with saliva of infected animals
Virus multiplies in skeletal muscle and connective tissue, then migrates to central nervous system, causing a rapidly progressing encephalitis Diagnosis Past - presence of Negri bodies (masses of virus particles or unassembled viral subunits) Today - immunological tests, virus isolation, as well as the detection of Negri bodies Rabies cases in the U.S Humans - about 10 per year Animals - about 8,000 per year
Hepatitis is any inflammation of the liver Currently eleven viruses are recognized as causing hepatitis Herpesviruses CMV and EBV - do not cause permanent liver damage Nine hepatotropic viruses Some have not been well characterized
Caused by hepatitis B virus (HBV), a dsDNA virus with a circular genome Virus is transmitted by Blood transfusions Contaminated equipment Unsterile needles Any body secretion Also transplacental transmission to fetus occurs
Caused by hepatitis C virus (HCV), an ssRNA virus within the family Flaviviridae Virus is spread by Intimate contact with virus-contaminated blood utero from mother to fetus In Fecal-oral route Organ transplants Diagnosis is by serological tests
Is caused by hepatitis D virus (HDV) (formally called the delta agent), which only causes disease if the individual is co-infected with hepatitis B virus Co infection may lead to a more serious acute or chronic infection than that normally seen with HBV alone Diagnosis is by serological tests
Treatment is difficult and often administration of alpha interferon involves Prevention and control is by the use of the hepatitis B vaccine Recently, hepatitis F and hepatitis G have been identified and are currently being investigated
More than 80% of U.S. adults older than 35 years have been exposed to CMV and carry a lifelong infection Most infections are asymptomatic but infection can be serious in immunologically compromised individuals
Virus persists in the body and is shed for several years in saliva, urine, semen, and cervical secretions Infected cells have intranuclear inclusion bodies Diagnosis is by viral isolation and serological tests Some antiviral agents are available for treatment, but only used in high-risk patients
Avoiding close personal contact with infected individual Use blood/organs from seronegative donors
Caused by herpes simplex type 2 (HSV-2), a dsDNA virus that is a member of Herpesviridae Virus is most frequently transmitted by sexual contact Disease has active and latent phases 1. Active Phase 2. Latent Phase
Virus rapidly reproduces Patient can be symptom free or painful blisters in the infected area may occur, as well as other symptoms Fever Burning Sensation Genital Soreness
after resolution of active phase virus retreats to nerve cells where the viral genome resides in the nuclei of host cells and can be periodically reactivated There is no cure, but acyclovir decreases healing time, duration of viral shedding, and duration of pain
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