Severe Fever with Thrombocytopenia Syndrome

Causative agent

Severe Fever with Thrombocytopenia Syndrome (SFTS) is an emerging infectious disease caused by SFTS virus in the family Phenuiviridae.

Clinical features

Common symptoms of STFS include fever and gastrointestinal symptoms (nausea, vomiting, diarrhoea, and melena), and are sometimes accompanied by abdominal pain, muscle pain, neurological symptoms, lymph node swelling, and bleeding symptoms. Severe infections can cause haemorrhagic fever and multiple organ failure leading to death. The mortality rate of SFTS ranged from 10 to 30%. The elderly (in particular female), and patients with haemorrhagic or neurologic manifestations are at risk of higher fatality.

Mode of transmission

SFTS is primarily transmitted to humans through the bite of certain kinds of ticks that carry SFTS virus. It can also be transmitted through direct contact with blood, secretions, excretions of the sick or deceased persons, or objects contaminated by them. Pets such as cats and dogs, as well as domestic animals like sheep and cattle in endemic areas, are important hosts for the ticks; close contact with these animals can increase the risk of infection. Although rare, transmission of SFTS may occur via ocular exposure to blood or other body fluids of infected patients.

Incubation period

The incubation period for SFTS is commonly 6 – 14 days.

Management

There is no specific treatment for SFTS, and management of patients primarily focuses on symptomatic treatment to relieve discomfort. For patients with severe SFTS, hospitalisation with supportive management is often necessary.

Prevention

The vectors transmitting SFTS are mainly found in vegetated areas; preventive measures should be taken when visiting rural areas to avoid being bitten by these vectors.

Pre-visit preparation:

• Wear loose, light-coloured, long-sleeved tops and trousers
• Wear shoes that cover the entire foot, avoid wearing sandals or open shoes
• Tuck trousers into socks or boots to prevent arthropods from reaching the skin
• Use DEET-containing insect repellent on exposed parts of the body and clothing
  • Pregnant women and children of 6 months or older can use DEET-containing insect repellent. In general, use DEET of up to 30% for pregnant women and up to 10% for children. For children who travel to countries or areas where tick-borne or mosquito-borne diseases are endemic or epidemic and where exposure is likely, children aged 2 months or above can use DEET-containing insect repellents with a concentration of DEET up to 30%.
• Avoid using fragrant cosmetics or skin care products
• If both insect repellents and sunscreen are used, apply insect repellents after sunscreen

During the visit:

• Stay on footpaths and avoid walking through vegetation. Do not brush along the vegetation at the sides of footpaths
• Avoid resting on vegetation, or at humid and dark places
• Do not hang clothing on trees or vegetation
• Do not feed wild or stray animals
• Re-apply insect repellents according to instructions

After the visit:

• Inspect body parts and clothing. Clear any attached arthropods carefully
• Take a soapy shower and wash the clothes
• Inspect and clean the bodies of accompanying pets

If an attached tick is found on the body:

• Gently remove it by grasping its head with tweezers or fine-tipped forceps close to the skin, then disinfect the bite area and wash hands with soap and water
• Do not crush or twist the tick during removal

Control of vectors and the reservoir of the diseases are also useful preventive measures:

• Disinfest your pets regularly
• Inspect and disinfest pet beddings regularly
• Trim vegetation particularly the grass in your premises

Besides, maintaining good personal hygiene is effective to prevent the spread of SFTS.

For details about the use of insect repellents and the key points to be observed, please refer to 'Tips for using insect repellents'.