The Centre for Health Protection has confirmed the first screwworm infestation of the year involving a 79-year-old Yuen Long man. 

The man has no recent travel history. He developed bleeding ulcers in his mouth, and maggots were found in his mouth on March 12. He sought medical treatment and is now in stable condition.

Screwworm, or Chrysomya bezziana, eat dead or living tissue, often burrowing deep into wounds. This can cause tissue damage, secondary invasion - and sometimes death.

There were four screwworm infestations reported last year, eight in 2004 and nine in 2003.

To avoid screwworm infestations:

* All wounds should be treated immediately, and properly cleaned and dressed;

* Use proofing measures, including window screens, to keep flies out;

* Observe good personal and environmental hygiene;

* Seniors homes workers should ensure good environmental hygiene, be alert to people developing symptoms of the disease and arrange for residents who feel unwell to see a doctor promptly.