Group Group V ((−)ssRNA) Family Bunyaviridae Species Heartland virus | Order Unassigned Genus Phlebovirus | |
The Heartland virus (HRTV) is a tick-borne phlebovirus of the Bhanja virus serocomplex discovered in northwestern Missouri by Dr. Scott Folk of Heartland Regional Medical Center in St. Joseph, Missouri. The virus was first proven to infect humans in June 2009 when two farmers, living 60 miles (97 km) apart, presented with fever, fatigue, diarrhea, thrombocytopenia, and leukopenia. The Lone Star Tick transmits the virus to people when feeding on blood.
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Classification
The Heartland virus is part of the Bunyaviridae family of viruses which contain 3 segments of -ssRNA. The genus of the virus is Phlebovirus and the species is the Heartland virus. The SFTS virus from China, discovered in 2011, is a related species causing a similar disease.
Transmission
The Heartland virus(HRTV) has been isolated from the Lone Star Tick (Amblyomma americanum) by researchers from the CDC and Missouri Western State University. Work continues as of 2013 to identify the reservoir host. The reservoir host is unknown, as HRTV has not been isolated from any wild or domestic animals. Many white-tailed deer and raccoon from northwestern Missouri had antibodies to HRTV, suggesting that these animals may be hosts. In a retrospective study using convenience samples of different animal sera only deer, raccoon, coyotes, and moose had antibodies against HRTV. They lived in thirteen states: Florida, Georgia, Illinois, Indiana, Kansas, Kentucky, Maine, Missouri, New Hampshire, North Carolina, Tennessee, Texas, and Vermont. The infections could have occurred as early as 2003, based on the estimated ages of affected deer.
Symptoms and signs
The following symptoms and signs have been reported: fever in excess of 100.4 °F (38 °C), lethargy (weakness), headaches, muscle pain (myalgia ), loss of appetite, nausea, diarrhea, weight loss, joint pain(arthralgia), low white blood cell count (leukopenia) and easy bruising from low platelet count(thrombocytopenia). Elevated liver transaminases may also be present.
Risk factors
All known 11 human cases have been reported from three U.S. states: Missouri, Tennessee, and Oklahoma. All currently known cases occurred between May and September and people spent a fair amount of time outdoors in regions where ticks were endemic; In all known cases people reported being bitten by ticks in the previous 14 days.
Diagnosis
Diagnosis is currently through the elimination of other causes of infectious diseases with related symptoms like ehrlichiosis and anaplasmosis or if the patient fails to respond to treatment with the antibiotic doxycycline. RT-PCR may then be used to detect viral ssRNA in the blood. Antibody titers against the virus may also be used to indicate infection with the Heartland virus.
Treatment
Treatment is non-specific. Antibiotics are not useful against viruses. Intravenous fluid administration and medications for the relief of pain are currently the best options.
Prevention
When planning to spend time outdoors in areas where the virus is known or suspected to be harbored by ticks, it is recommended that one cover the body completely with long sleeves and pants, and to avoid bushy and wooded areas. Although ticks are not consistently repelled by DEET-containing repellents, insect repellents should still be applied to one's body and gear. It is recommended that one perform thorough tick checks after being outside, and to remove any tick immediately. If a tick is found, one should remove the tick by the head, preferably with a pair of fine-tipped tweezers. Squeezing the abdomen of a tick while it is attached can force viruses and bacteria into the wound, increasing the chance of infection. Crushing an unattached tick will also release bacteria and viruses from its abdomen, which may then be able to enter a wound or burrow through the skin.