Specific Agents

Filoviridae

Arenaviridae

Bunyaviridae

Flaviviridae

• Ebola virus
• Marburg virus

• Flexal virus
• Guanarito virus
• Junin virus
• Lassa fever virus
• Machupo virus
• Sabia virus

• Crimea-Congo hemorrhagic fever virus
• Rift Valley fever
• Hantaan virus

• Dengue virus
• Kyasanur forest disease virus
• Omsk hemorrhagic fever virus
• Yellow fever virus

Symptoms

Abdominal pain

Bleeding

CNS effects

Conjunctivitis

Cough

Disseminated intravascular coagulation

Fever

Flushing

Headache

Hemorrhage

Hepatitis

Jaundice

Loss of appetite

Lymphadenopathy

Meningoencephalitis

Myalgia

Nausea

Pericardial effusion

Petechiae

Pharyngitis

Photophobia

Pleural effusion

Pneumonia

Prostration

Rash

Retinitis

Retroorbital pain

Sore throat

Splenomegaly

Ulceration

Vomiting

Differential Diagnosis

Malaria may need to be eliminated in most cases. Viral encephalitides may also have to be eliminated as headaches are a common symptom. Other infectious diseases that may need to be eliminated include:

• Borreliosis;
• Hemorrhagic smallpox
• Influenza;
• Leptospirosis;
• Measles;
• Psittacosis;
• Rickettsioses;
• Salmonellosis;
• Sepsis from Gram-negative bacteria;
• Septicemic plague;
• Shigellosis;
• Staphylococcal sepsis;
• Toxic shock syndrome;
• Trypanosomiasis;
• Viral hepatitis

Diseases or poisoning of organs where signs and symptoms listed above have been seen have to be eliminated. Clotting disorders including thrombocytopenias, leukemia, and connective tissue disorders may have to be considered.

Risk Groups

First Indications

Surge Period

These diseases have incubation periods in the range 2- 21 days although 3-10 days after inoculation is when most cases are likely to develop. In an attack that is a single point event there is likely to be a surge of cases within 2-3 days of the first cases that will peak after about a week to 10 days.

If the attack is conducted by release of infected mosquito or tick vectors the surge may be slower to appear and longer lasting.

Treatment options

The American Medical Association recommends that all clinically evident viral hemorrhagic fever cases should be treated with ribavirin until the etiologic agent has been identified. Treatment can be continued when the agent is identified as an Arenavirus or Bunyavirus and discontinued otherwise. The recommended treatment is 30 mg/kg up to maximum of 2 g as a loading dose followed by 2 doses of 1 g per day for ten days. For contained casualty incidents (low numbers of exposed), the drug can be supplied intravenously. In mass casulaty incidents, it should be given orally.

Ribavirin is not approved for such use in the United States and would only be available for compassionate use as an Investigative New Drug.

Supportive treatments may include maintaining blood volume and ionic balance. Intravenous infusion should be avoided because of the possibility of bleeding around the catheter.

Precautions for health care personnel

Barrier precautions should be initiated and, if possible, patients should be in negative pressure rooms. Patient to patient transmission has been seen for some of these viruses and precautions for health care workers must be instituted immediately and enforced vigorously. Include:

• Hand washing before and after donning and removal of protective equipment;
• Double gloves
• Impermeable gowns, eye shields (including goggles) and leg and shoe coverings;
• Respirators;
• Dedicated medical equipment;
• Frequent disinfection of surfaces.

Biological samples for laboratory diagnosis and body fluids should be handled at the highest level of biological containment available and sent only to laboratories qualified to handle them.

Vaccines

Vector Involvement

• Arenaviruses are carried by specific rodent hosts in their home areas. They are well adapted to these hosts and may not become established in other rodents.
• Bunyaviruses are carried by ticks or culicine mosquitoes.
• Filovirus vectors and reservoirs are not known.
• Flaviviruses are carried by ticks or mosquitoes.

Animal involvement and indicators

The only one of these viruses that shows significant involvement with livestock is Rift Valley fever virus. It can cause significant fatalities in sheep and goats and it may be necessary to slaughter or quarantine local flocks. Dengue virus will use local mammals, include livestock and vermin, as hosts and monitoring and control of these animals will be necessary in the aftermath of an incident. Vector-borne viruses with mammalian hosts include:

• Crimean-Congo
• Dengue
• Hantaan
• Omsk
• Rift Valley
• Yellow fever

Other viruses either have very specific host requirements, such as Junin or Machupo viruses, or have no known mammalian hosts.