1. Severe Fever with Thrombocytopenia Syndrome (SFTS) is an emerging infectious disease that is endemic in China, Japan and South Korea. It is caused by a member of the Bunyaviridae family of viruses and is most commonly transmitted from infected animals (e.g. goats, cattle, dogs, chickens, pigs and rodents) to humans via a tick bite. There is no evidence to suggest that the main vector, Haemaphysalis longicornis, is established in tropical environment, such as in Singapore. Person-to-person transmission through contact with blood or respiratory secretions from an infected person has also been reported, but is rare. The incubation period of the disease is 9 days on average (5-14 days range).
2. The peak season for SFTS is typically between spring and summer, which corresponds with the seasonal life cycle of the tick vector and the increased outdoor activity during summer. The Korean Centers for Disease Control and Prevention (KCDC) has reported the first case of SFTS in 2018 while Japan and China have not reported cases thus far. Both KCDC and China have since advised the public to take precautionary measures in preventing tick bites. To date, there are no indications of unusual trends in STFS in these endemic countries. Please refer to Table 1 below for the annual number of SFTS reported by South Korea, Japan and China.
Table 1. Annual number of SFTS reported in South Korea, Japan and China, 2013 – 2018
No of cases
No of deaths
No of cases
No of deaths
No of cases
No of deaths
3. The importation of an SFTS case via an infected traveller is possible in view of the approaching SFTS season and the high travel volume between SFTS endemic countries and Singapore. While the likelihood of exposure during travel might increase during times of seasonal flare-ups, the risk of acquisition can be significantly reduced if travellers are informed and aware of the risk, and if basic tick-bite precautionary measures are followed. Most of the SFTS cases reported were from wooded and hilly areas.
4. In the event of an imported case, the risk of sustained transmission in the community is low, as the main vector, Haemaphysalis longicornis, is restricted to temperate regions of the world.
5. If a case were to occur locally, persons most at risk of secondary infection would be those in close contact with the blood and bodily fluids of the case. These would include healthcare workers, laboratory workers handling specimens, and also family members who would have provided direct nursing care for the case prior to diagnosis. Delays in the identification of cases can pose risks to healthcare facilities. However, observances of standard precautions in well-resourced settings are sufficient to prevent onward transmission.
6. Case definition to identify patients for investigation:
An acutely ill person with acute onset of
- Fever AND
- Thrombocytopenia AND
- Influenza-like symptoms (myalgia) OR gastrointestinal symptoms (nausea, vomiting, diarrhea) AND
- With onset of symptoms occurring within 14 days of travel to a country where there is ongoing SFTS virus transmission AND relevant exposure risk (e.g. outdoor activities such as hiking or farm stay).
7. Blood samples (~3mL) should be taken using red or yellow topped tubes and sent to National Public Health Laboratory (NPHL) for SFTS PCR, together with the MOH Surveillance Submission Form.
8. The clinical manifestations of SFTS are non-specific and similar to several diseases. It is important to exclude other conditions such as dengue, severe bacterial sepsis, rickettsiosis, leptospirosis and Zika virus infection.
9. A significant proportion of persons exposed to the SFTS virus probably develop mild infection or are asymptomatic, but the exact proportion is not known. The clinical course of most observed cases of SFTS can be divided into 3 phases, with an estimated mortality rate that is between 6-30%.
- Febrile phase (5-11 days): SFTS begins with a non-specific prodrome, with fever, anorexia, myalgia and gastrointestinal symptoms (including nausea, vomiting and diarrhea). Regional, especially inguinal, lymphadenopathy is common. Leukopenia, thrombocytopenia, elevated serum levels of alanine/aspartate aminotransferase (ALT/AST), alkaline phosphatase (ALP), lactate dehydrogenase (LD), and creatine kinase (CK), and prolongation of activated partial thromboplastin time may be expected.
- Critical phase (7-14 days): In the second week of illness, complications of multiple organ dysfunction can occur, including acute renal failure, cardiac arrhythmias, myocarditis and meningoencephalitis. Patient may develop haemorrhagic manifestations with mucosal bleeding or disseminated intravascular coagulopathy. Sustained platelet decline, elevations in AST, LDH, CK, CKMB are major risk factors for death.
- Convalescent phase (11 to 19 days): Clinical symptoms and biochemical abnormalities resolve during this phase.
10. Patients under investigation with signs of severe illness should be hospitalized and monitored for complications. Patients under investigation well enough to be managed as outpatient can be managed as outpatient or referred to the National Centre for Infectious Diseases (NCID) the next working day for review. There is no specific anti-viral treatment available and management is supportive. Persons who are under investigation or confirmed to have SFTS do not require isolation but should strictly be placed on standard precautions, with droplet precautions for aerosol-generating procedures.
11. Close contacts of persons with confirmed STFS should be advised to monitor themselves for the development of fever for the duration of incubation period (i.e. 14 days), and to seek medical attention early if this occurs.
12. Laboratory staff handling specimens should take precautions as for bloodborne pathogens, according to laboratory protocol.
NOTIFICATION TO MOH
13. All patients under investigation and confirmed cases of SFTS should be notified to MOH via submission of MD131 notification of infectious diseases form (under ‘Other significant disease’) through the Communicable Diseases Live & Enhanced Surveillance (CDLENS) system at www.cdlens.moh.gov.sg, or by fax to 6221-5528/38.
14. Please disseminate this alert to the relevant staff for their attention.
Communicable Diseases Division National Centre for Infectious Diseases
Ministry of Health, Singapore
Date: 25 May 2018