Intermittent outbreaks continued throughout the Atlantic seaboard for the next 100 years
Second isolated virus was Eastern equine encephalitis virus (EEEV) in Virginia in 1933
Third isolated virus was Venezuelan equine encephalitis vires (VEEV) in 1936
Outbreaks almost always occurred during the summer
First outbreaks occurred as summertime epidemics of polyarthritis in Australia and New Guinea in 1928
CHIKV was isolated first in Tanzania in 1953 from the blood of humans with severe athritis
Enveloped (+)ssRNA viruses
In mice, virus primarily infects muscles and fibroblasts
Induce substantial viremia to spread to other skeletal muscle
In-vector incubation time requires 2-7 days for infectivity
For children, 1 in 8 infections results in encephalitis
For adults, 1 in 23 infections results in encephalitis
Epizootic cycle appears every 5 to 10 years and is associated with heavy rainfall and warmer water
Approximately 8 human cases occur every year in the US
These viruses are common and widespread in the Old World
Most common viruses are CHIKV and Ross River virus
CFR is ~1 in 1000 with most deaths in neonates
May be maintained in mosquitoes via vertical transmission
CHIKV incubation time of 3-12 days
Rash appears 4-8 days after initial illness
If muscles primarily hurt, probably dengue
Other symptoms include conjunctivitis (not as common for Dengue), headache, GI complaints
Rash may cause a second rise in fever and be itchy
Leukopenia is common
There are specific rtPCR primers for all alphaviruses and IgM serologies are very specific
First discovered in mosquitoes in 1943 during a yellow fever outbreak
No documnated cases of human-to-human transmissions
Incubation time of 2-6 days
Typically: Fever, generalized weakness, back pain, dizziness. Most recover in a few days
Diagnose with standard PCR, ELISA-Ag, ELISA-IgM
No specific treatment and generally not necessary
Typically: Sudden onset with headache, high fever, back pain, joint pain, stomach pain, vomiting (influenza-life syndrome)
Commonly: Conjunctivitis, flushed face, palatal petechiae
Occasionally: Jaundice, mood changes, sensory misperception
Progresses to uncontrolled bleeding, bruising starting of day 4 with CFR = 10-50%
Diagnosis: Same as Rift Valley Fever
Treatment: Sensitive in vitro to Ribavirin. Supportive care in shock phase.
Viruses (there are several that cause this) are found worldwide, but outbreaks previously occurred mostly in Asia
Transmission is identical HPS with aerosolized excreta
Incubation time is 1-2 weeks usually but can take up to 8 weeks
Sudden onset headaches, back and abdominal pain, fever, chills, nausea, and blurred vision
In less than 5% progresses to hypotension, shock, and acute renal failure
Diagnosis: Same as above
Treatment: Supportive
Enveloped, segmented (-)ssRNA virus
Life cycle restricted to cellular cytoplasm
Similar to Ebola, it encodes RNA-dependent RNA polymerase
Old World (Lassa Fever) and New World are similar except that neurologic symptoms, -penias, and bleeding are less common for Old World viruses
Incubation time of 5-20 days
Disease begins with fever, chills, malaise, anorexia, headache, and myalgias
During symptom onset they may experience swelling and bleeding gums, swelling and bleeding conjunctiva
Patients often develop petechiae from thrombocytopenia
Patients often experience bradycardia and orthostatic hypotension
During second week patients either begin to recover or begin to die
Isolation in Vero cells
rtPCR
Fatal cases can be diagnosed with immunohistochemistry with fixed tissue
Neutralization assay is useful if specific convalescent serum is available
For ANF, secondary pneumonias are common
Platelets, activated factor VII, desmopressin, and transfusion have not been systemically evaluated
In pregnant patients, abortion improves survival of mother
High-throughput screens with pseudo-typed virus indentifies several in vitro viral entry inhibitors