Severe Fever with Thrombocytopenia Syndrome (SFTS) is a serious, emerging infectious disease that represents a significant concern for public health. This viral illness is characterized by the sudden onset of symptoms, which can rapidly progress to severe complications. The disease is associated with mortality rates that can reach as high as 30% in certain areas. Understanding the cause, recognizing the signs of infection, and knowing the methods of transmission and prevention is important for people living in or traveling to regions where the disease is established.
Defining the SFTS Virus and Its Range
The illness is caused by the Severe Fever with Thrombocytopenia Syndrome virus (SFTSV), classified within the genus Bandavirus of the family Phenuiviridae. This classification places it among viruses often transmitted by arthropods, such as ticks. SFTS is considered a zoonotic disease, naturally transmitted between animals and humans.
The virus was first identified in China in 2009 and is now endemic across several countries in East Asia. The primary regions reporting SFTS cases are central and eastern China, South Korea, and Japan. The disease is most prevalent in rural areas, with a majority of cases occurring between spring and early autumn (March to November). The virus is maintained in nature through a cycle involving ticks and various animal hosts, making people who live or work in agricultural and forested environments the most commonly affected demographic.
Clinical Signs and Disease Progression
The incubation period for SFTS typically ranges from six to 14 days following exposure. The illness begins abruptly with non-specific symptoms, including a sudden, high fever, generalized fatigue, muscle pain (myalgia), and headache. Patients often experience gastrointestinal issues, such as nausea, vomiting, diarrhea, and abdominal pain.
A laboratory hallmark is the simultaneous reduction in two types of blood cells. Patients consistently show thrombocytopenia (low platelet count) and leukopenia (reduced white blood cell count). This decline in platelets can lead to hemorrhagic manifestations, such as easy bruising, petechiae, and mucosal bleeding in severe cases.
As the illness progresses, usually into the second week, some patients enter a severe phase characterized by multiple organ dysfunction. This deterioration can involve liver and kidney impairment, reflected in elevated liver enzyme levels and signs of acute renal failure. The most serious form of the disease can lead to shock, neurological disturbances, and disseminated intravascular coagulation (widespread clotting and bleeding). Patients who survive typically enter a convalescent phase where symptoms and laboratory abnormalities gradually resolve over several weeks.
How SFTS Spreads and Effective Prevention
The primary way SFTS is transmitted to humans is through the bite of an infected tick, establishing it as a tick-borne zoonosis. The most significant vector identified is the hard-bodied tick Haemaphysalis longicornis, which is widely distributed across the endemic regions. These ticks acquire the virus by feeding on infected animals and transmit it to humans during a subsequent blood meal.
Domestic animals, including cattle, sheep, goats, dogs, and cats, play a role as amplifying hosts in the virus cycle. While these animals often show antibodies to the virus, humans are generally considered accidental hosts.
Although less common, human-to-human transmission of SFTSV has been documented, primarily through direct contact with blood or other bodily fluids from an infected person. This secondary spread often occurs in healthcare settings among caregivers who have close contact with severe cases, highlighting the need for appropriate infection control measures. Transmission via contaminated instruments or percutaneous exposure, such as a needle-stick injury, has also been reported.
Preventing infection largely revolves around avoiding tick bites, especially for people who spend time outdoors in rural, grassy, or forested areas during the warmer months.
Prevention Measures
- Wear protective clothing, such as long-sleeved shirts and pants, and tuck pants into socks to limit skin exposure.
- Apply insect repellents containing active ingredients like DEET to exposed skin and clothing.
- Perform a thorough check of the body and clothing for ticks after outdoor activities.
- Remove any attached ticks promptly and correctly using fine-tipped tweezers.
Confirmation and Patient Care
Diagnosis of SFTS begins with recognizing the clinical picture, which includes the sudden onset of fever and the characteristic low blood cell counts. A patient’s history of being in an endemic area or reporting a tick bite strongly supports the possibility of SFTS infection.
Laboratory confirmation is necessary, typically achieved by detecting the virus’s genetic material using reverse transcription-polymerase chain reaction (RT-PCR) in serum samples. Serological testing, such as enzyme-linked immunosorbent assay (ELISA), is another diagnostic approach used to look for specific IgM and IgG antibodies.
Currently, there is no specific antiviral drug or vaccine widely approved for the treatment or prevention of SFTS. Patient care is primarily supportive, focusing on managing symptoms and maintaining the function of vital organs. Supportive care includes careful monitoring of fluid and electrolyte balance, pain management, and addressing complications such as organ failure or hemorrhagic tendencies. While antiviral agents like favipiravir have been considered, their overall effectiveness in treating SFTS remains under evaluation. Early diagnosis and prompt supportive interventions are the most effective strategies to improve outcomes for patients.