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Viral hemorrhagic fevers (VHFs) refer to a group of illnesses that are caused by several distinct families of viruses. In general, the term "viral hemorrhagic fever" is used to describe a severe multisystem syndrome (multisystem in that multiple organ systems in the body are affected). Characteristically, the overall vascular system is damaged, and the body's ability to regulate itself is impaired. These symptoms are often accompanied by hemorrhage (bleeding); however, the bleeding is itself rarely life-threatening. While some types of hemorrhagic fever viruses can cause relatively mild illnesses, many of these viruses cause severe, life-threatening disease. The Special Pathogens Branch (SPB) primarily works with hemorrhagic fever viruses that are classified as biosafety level four (BSL-4) pathogens. A list of these viruses appears in the SPB disease information index. The Division of Vector-Borne Infectious Diseases, also in the National Center for Infectious Diseases, works with the non-BSL-4 viruses that cause two other hemorrhagic fevers, dengue hemorrhagic fever and yellow fever.
VHFs are caused by viruses of four distinct families: arenaviruses, filoviruses, bunyaviruses, and flaviviruses. Each of these families share a number of features:
In rare cases, other viral and bacterial infections can cause a hemorrhagic fever; scrub typhus is a good example.
Viruses associated with most VHFs are zoonotic. This means that these viruses naturally reside in an animal reservoir host or arthropod vector. They are totally dependent on their hosts for replication and overall survival. For the most part, rodents and arthropods are the main reservoirs for viruses causing VHFs. The multimammate rat, cotton rat, deer mouse, house mouse, and other field rodents are examples of reservoir hosts. Arthropod ticks and mosquitoes serve as vectors for some of the illnesses. However, the hosts of some viruses remain unknown -- Ebola and Marburg viruses are well-known examples.
Taken together, the viruses that cause VHFs are distributed over much of the globe. However, because each virus is associated with one or more particular host species, the virus and the disease it causes are usually seen only where the host species live(s). Some hosts, such as the rodent species carrying several of the New World arenaviruses, live in geographically restricted areas. Therefore, the risk of getting VHFs caused by these viruses is restricted to those areas. Other hosts range over continents, such as the rodents that carry viruses which cause various forms of hantavirus pulmonary syndrome (HPS) in North and South America, or the different set of rodents that carry viruses which cause hemorrhagic fever with renal syndrome (HFRS) in Europe and Asia. A few hosts are distributed nearly worldwide, such as the common rat. It can carry Seoul virus, a cause of HFRS; therefore, humans can get HFRS anywhere where the common rat is found. While people usually become infected only in areas where the host lives, occasionally people become infected by a host that has been exported from its native habitat. For example, the first outbreaks of Marburg hemorrhagic fever, in Marburg and Frankfurt, Germany, and in Yugoslavia, occurred when laboratory workers handled imported monkeys infected with Marburg virus. Occasionally, a person becomes infected in an area where the virus occurs naturally and then travels elsewhere. If the virus is a type that can be transmitted further by person-to-person contact, the traveler could infect other people. For instance, in 1996, a medical professional treating patients with Ebola hemorrhagic fever (Ebola HF) in Gabon unknowingly became infected. When he later traveled to South Africa and was treated for Ebola HF in a hospital, the virus was transmitted to a nurse. She became ill and died. Because more and more people travel each year, outbreaks of these diseases are becoming an increasing threat in places where they rarely, if ever, have been seen before.
Viruses causing hemorrhagic fever are initially transmitted to humans when the activities of infected reservoir hosts or vectors and humans overlap. The viruses carried in rodent reservoirs are transmitted when humans have contact with urine, fecal matter, saliva, or other body excretions from infected rodents. The viruses associated with arthropod vectors are spread most often when the vector mosquito or tick bites a human, or when a human crushes a tick. However, some of these vectors may spread virus to animals, livestock, for example. Humans then become infected when they care for or slaughter the animals. Some viruses that cause hemorrhagic fever can spread from one person to another, once an initial person has become infected. Ebola, Marburg, Lassa and Crimean-Congo hemorrhagic fever viruses are examples. This type of secondary transmission of the virus can occur directly, through close contact with infected people or their body fluids. It can also occur indirectly, through contact with objects contaminated with infected body fluids. For example, contaminated syringes and needles have played an important role in spreading infection in outbreaks of Ebola hemorrhagic fever and Lassa fever.
Specific signs and symptoms vary by the type of VHF, but initial signs and symptoms often include marked fever, fatigue, dizziness, muscle aches, loss of strength, and exhaustion. Patients with severe cases of VHF often show signs of bleeding under the skin, in internal organs, or from body orifices like the mouth, eyes, or ears. However, although they may bleed from many sites around the body, patients rarely die because of blood loss. Severely ill patient cases may also show shock, nervous system malfunction, coma, delirium, and seizures. Some types of VHF are associated with renal (kidney) failure.
Patients receive supportive therapy, but generally speaking, there is no other treatment or established cure for VHFs. Ribavirin, an anti-viral drug, has been effective in treating some individuals with Lassa fever or HFRS. Treatment with convalescent-phase plasma has been used with success in some patients with Argentine hemorrhagic fever.
With the exception of yellow fever and Argentine hemorrhagic fever, for which vaccines have been developed, no vaccines exist that can protect against these diseases. Therefore, prevention efforts must concentrate on avoiding contact with host species. If prevention methods fail and a case of VHF does occur, efforts should focus on preventing further transmission from person to person, if the virus can be transmitted in this way.Because many of the hosts that carry hemorrhagic fever viruses are rodents, disease prevention efforts include
For hemorrhagic fever viruses spread by arthropod vectors, prevention efforts often focus on community-wide insect and arthropod control. In addition, people are encouraged to use insect repellant, proper clothing, bednets, window screens, and other insect barriers to avoid being bitten. For those hemorrhagic fever viruses that can be transmitted from one person to another, avoiding close physical contact with infected people and their body fluids is the most important way of controlling the spread of disease. Barrier nursing or infection control techniques include isolating infected individuals and wearing protective clothing. Other infection control recommendations include proper use, disinfection, and disposal of instruments and equipment used in treating or caring for patients with VHF, such as needles and thermometers. In conjunction with the World Health Organization, CDC has developed practical, hospital-based guidelines, titled Infection Control for Viral Haemorrhagic Fevers In the African Health Care Setting. The manual can help health-care facilities recognize cases and prevent further hospital-based disease transmission using locally available materials and few financial resources.
Scientists and researchers are challenged with developing containment, treatment, and vaccine strategies for these diseases. Another goal is to develop immunologic and molecular tools for more rapid disease diagnosis, and to study how the viruses are transmitted and exactly how the disease affects the body (pathogenesis). A third goal is to understand the ecology of these viruses and their hosts in order to offer preventive public health advice for avoiding infection.
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World Trade Center Attack Memorial - September 11, 2001 Breaking News From GOD: April 17, 2006 11:25 AM
Send mail to Webmaster (at) Twin-Towers.net with questions or comments about
this web site. On Tuesday, September 11, 2001, at 8:45am New York local time, One World Trade Center, the north tower, was hit by a hijacked 767 commercial jet airplane, loaded with fuel for a trans-continental flight. Two World Trade Center, the south tower, was hit by a similar hijacked jet 18 minutes later at 9:03am. (In separate but related attacks, the Pentagon building near Washington D.C. was hit by a hijacked 757 at 9:43am, and at 10:10am, a fourth hijacked jetliner crashed in Pennsylvania.) The south tower, WTC 2, which had been hit second, was the first to suffer a complete structural collapse at 10:05am, 62 minutes after being hit itself, 80 minutes after the first impact. The north tower, WTC 1, then also collapsed at 10:29am, 104 minutes after being hit. WTC 7, a substantial 47 story office building in its own right, built in 1987, was damaged by the collapsing towers, caught fire, and later in the afternoon also totally collapsed.
The list of collapsed buildings (as confirmed by the New York Times through Saturday, 2001.0915) included all seven buildings of the World Trade center complex — including WTC 6, the U.S Customs House to the north; WTC 3, the 22 story Marriot World Trade Center hotel just west of Tower Two; and WTC 4 and 5, the Plaza Buildings to the east (although satellite images suggest much of WTC 5, the north Plaza Building, was still standing). Other nearby buildings were significantly damaged, including the St. Nicholas Greek Orthodox Church, and One Liberty Plaza, a 54 floor, 743' tall building across Church Street to the east. About 2800 people died in the attack. The recovery and site clearing process officially concluded on May 30, 2002 with 1796 people still remain unrecovered. 1.8 million tons of debris was removed from the disaster site. Yahoo! Buzz Index Overall Leaders 1. Jennifer Lopez 2. Britney Spears 3. Euro 2004 4. Harry Potter and the Prisoner of Azkaban 5. Usher 6. 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Grand Theft Auto: San Andreas 14. Zelda 15. Mega Man Yahoo! Buzz Index Video Games Movers 1. NBA Live 2004 2. SOCOM 2 3. EverQuest 4. Pokemon Crater 5. Starcraft Cheats 6. Silent Hill 4 7. Battlefield 1942 8. Command and Conquer 9. Fire Emblem 10. Mortal Kombat 11. Final Fantasy X-2 12. Sonic 13. Counter-Strike Hacks 14. FFX 15. MVP Baseball 2004 Yahoo! Buzz Index Networks Leaders 1. ESPN 2. Cartoon Network 3. Nickelodeon 4. BBC 5. CNN 6. Disney Channel 7. MTV 8. Weather Channel 9. Food Network 10. CBS 11. QVC 12. Fox News 13. Univision 14. MSNBC 15. PBS Yahoo! Buzz Index Baseball Leaders 1. Chicago Cubs 2. New York Yankees 3. Houston Astros 4. Boston Red Sox 5. Los Angeles Dodgers 6. San Francisco Giants 7. Texas Rangers 8. San Diego Padres 9. St. Louis Cardinals 10. Cincinnati Reds 11. Philadelphia Phillies 12. Atlanta Braves 13. Chicago White Sox 14. Milwaukee Brewers 15. Anaheim Angels Yahoo! Buzz Index Basketball Leaders 1. Detroit Pistons 2. Los Angeles Lakers 3. 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