Emerging Infectious Diseases

1) Ebola Hemorrhagic Fever (Ebola virus disease)

Ebola is one of the important emerging infectious diseases that begins with fever, headache, vomiting, and diarrhea. Later, bleeding into the gastrointestinal tract occurs, followed by shock and disseminated intravascular coagulation. The hemorrhages are caused by severe thrombocytopenia. The mortality rate associated with this virus approaches 100%. Most cases arise by secondary transmission from contact with the patient’s blood or secretions (e.g., in hospital staff). Reuse of needles and syringes is also implicated in the spread within hospitals. Although greatly feared, Ebola hemorrhagic fever is quite rare.

Monkeys can be infected but, because they become sick, are unlikely to be the reservoir. Bats are suspected of being the reservoir, but this has not been established. The high mortality rate of Ebola virus is attributed to several viral virulence factors: Its glycoprotein kills endothelial cells, resulting in hemorrhage, and two other proteins inhibit the induction and action of interferon. Lymphocytes are killed, and the antibody response is ineffective.

Diagnosis is made by isolating the virus or by detecting a rise in antibody titer. (Extreme care must be taken when handling specimens in the laboratory.) No antiviral therapy is available. Treatment with immune serum globulins containing antibody to Ebola virus has had variable results.

Prevention centers on limiting secondary spread by proper handling of patient’s secretions and blood. There is no vaccine.

2) Middle East Respiratory Syndrome (MERS)

Middle East Respiratory Syndrome (MERS) is a respiratory disease, which was reported first in Suadi Arabia in 2012, that is caused by viruses. This disease is new to human beings. Middle East Respiratory Syndrome Coronavirus (MERS-CoV) is the virus responsible for MERS. Corona virus infections are usually common in human that present as mild to moderate cold-like illnesses. But, MERS-CoV infection is different from other coronavirus infections previously found in humans.

MERS infected people had mild symptoms or no symptoms at all, but many MERS-CoV infected humans developed severe respiratory symptoms. They had cough, fever and shortness of breath. Others symptoms like gastrointestinal symptoms, like nausea/vomiting and diarrhea and kidney dysfunction. MERS can even be a fatal disease. Many people infected with MERS have died.

3) Chikungunya Virus

This virus causes chikungunya fever is another important emerging infectious disease characterized by the sudden onset of high fever and joint pains, especially of the wrists and ankles. A macular or maculopapula rash over much of the body is common. Outbreaks involving millions of people in India, Africa, and the islands in the Indian Ocean have occurred in the years from 2004 to 2006. Chikungunya virus is an RNA enveloped virus and is a member of the Togavirus family. It has a single-stranded, positive-polarity RNA genome. It is transmitted by species of Aedes mosquitoes, both Aedes aegypti and Aedes albopictus. The latter mosquito is found in the United States, so the potential for outbreaks exists. Individuals returning to the United States from areas where outbreaks have occurred have been diagnosed with chikungunya fever. Laboratory diagnosis involves detecting the virus in blood either by culturing or by enzyme-linked immunosorbent assay (ELISA). Antibody tests for either IgM or a rise in titer of IgG can also be used to make a diagnosis. There is no antiviral therapy, and no vaccine is available.