Findings into the source of the recent SARS outbreak in Beijing and Anhui Province

It has been more than two months since the Ministry of Health of China notified WHO and the world about an outbreak of SARS in Beijing and Anhui Province.

Since then, WHO experts have been supporting the Chinese authorities in their investigation into the cause of the laboratory-acquired cases, and in assessing the effectiveness of measures taken to control the outbreak.

On July 1 2004, the Ministry of Health of China released its status report on the investigation.

While the outbreak has now been successfully contained, initial findings from the investigation and the assessment of control measures have raised several important lessons for global public health.

Investigation into the source of the outbreak

During the course of the investigation, a significant amount of information was gathered, although all the practices within the National Institute of Virology in Beijing have yet to be thoroughly assessed. Although not all detailed information has been made available to WHO, the following conclusions have been made about the source of the outbreak:

• The National Institute of Virology in Beijing was the most likely source of the outbreak.
• At least four individuals may have been infected with SARS at the Institute. These include the two laboratory workers reported in April, and two additional laboratory workers. These two additional laboratory workers appear to have suffered from SARS-like illnesses in early February 2004. Recent laboratory tests performed at a national reference laboratory were positive for SARS antibodies.
• The use of inactivated SARS coronavirus, which was not tested to determine the effectiveness of the inactivation, in a general laboratory at the Institute appears the most likely cause of the outbreak.

During the investigation, it became apparent that all the positive laboratory workers worked in the same general laboratory at the Institute. Although no research involving live SARS viruses was known to have taken place in this laboratory, SARS coronavirus that had been inactivated in a Biosafety Level 3 laboratory in the Institute was used on several occasions during the early months of 2004 in experiments carried out in this area. The timing of the use of inactivated SARS coronavirus in the general laboratory coincides with the presence there of all the positive workers and with their likely incubation periods.

WHO recommends that further work is needed to verify the effectiveness of the method used to inactivate the live SARS virus. At the same time, other possible explanations of the cause of the outbreak cannot be fully excluded.

Biosafety concerns raised by the outbreak

The incident at the National Institute of Virology in Beijing has raised concerns about biosafety in general, and the way in which inactivated viral material is handled in particular.

''In light of the investigation, WHO believes that Member States should carefully review biosafety standards and strengthen them to avoid further incidents,'' said Dr Shigeru Omi, Regional Director of WHO's Western Pacific Region.

WHO will be working with Member States and expert groups to develop country and regional strategies to strengthen biosafety. Core components of such biosafety programmes at country level are likely to include:

• A containment policy to reduce the number of laboratories storing and working on SARS coronavirus.
• A legislative framework and independent advisory body to assist in the development, implementation and evaluation of a national biosafety programme and in the investigation of biohazard incidents and the dissemination of lessons learned to the global scientific community.
• A laboratory accreditation system based on standardized biosafety criteria.
• An occupational health service to monitor the well being of laboratory workers.

Comprehensive biosafety and training programmes in all diagnostic and research institutes supported by a management framework that facilitates compliance with evidence-based guidelines and the adoption of a positive biosafety culture.

WHO also emphasizes that scientists working with highly pathogenic viruses such as SARS need to handle inactivated material with the utmost caution. In particular, WHO recommends that:

• Researchers use appropriate and internationally accepted methods for validating the inactivation of live viruses.
• Inactivated material should be handled only in laboratories at biosafety level (BSL) 2 or above.
• Researchers handling inactivated material should wear appropriate personal protective equipment.
• New methods for inactivation should be adopted only after rigorous testing. -- Clear and comprehensive protocols should be available for all inactivation techniques.

Assessment of effectiveness of outbreak control measures

In addition to supporting the investigation into the possible source of the outbreak, WHO has worked with Chinese authorities to evaluate the effectiveness of the outbreak control measures.

Joint WHO-Ministry of Health teams have visited all the hospitals where the recent cases were treated before they were admitted to designated SARS facilities. In addition, WHO experts have reviewed data on contact tracing and other control measures.

''Overall,'' said Dr Omi, ''WHO believes that the Chinese authorities acted swiftly and effectively to control the outbreak once the alarm had been raised. Extensive contact tracing was undertaken in a matter of hours, and the effective isolation of cases and identification of contacts appears to have ensured that the outbreak was contained with remarkable speed.'' However, there was a delay in detecting the initial cases. As a consequence, two generations of transmission occurred and the application of effective hospital and community control measures took place late in the outbreak. The Ministry of Health of China has acknowledged this and is looking to strengthen further the current detection and response system. There are a number of lessons from this outbreak that are important globally, for Member States and for WHO itself:

• Health care workers, laboratory workers and people in close contact with certain animals are at risk of contracting a range of infectious diseases with outbreak potential. Disease detection systems need to be designed to take these risk factors, as well as clinical information, into account -- and to be robust enough to ensure that nobody slips through the net and evades detection.
• Health care workers need to be aware of the risks associated with certain occupations (including their own) and to be able to take a detailed occupational history from a patient.
• Health care workers also need to be aware of the importance of asking about the health of close contacts of anyone with a potentially contagious respiratory illness. Quickly identifying possible clusters of respiratory illness is important in the control of such diseases and the detection of new or rare infectious diseases.
• All health care workers should be empowered to initiate effective measures to protect themselves and others from potentially contagious diseases, in a ''safety first'' approach. This means that health care workers should be aware of potential clinical and epidemiological risk factors; have ready access to the equipment and knowledge needed to protect themselves and others; and be allowed to initiate the most appropriate infection-control measures immediately -- with validation and approval from senior members of staff later.

This recent outbreak has demonstrated once again that SARS is a containable disease. WHO commends the Chinese authorities for taking swift action to control the latest outbreak. WHO will be working closely with the Chinese authorities to assist in the strengthening of biosafety, and to build a long-term strategy for strengthening laboratory research and diagnosis in China.

WHO looks forward to working with China in its efforts to tackle SARS and other public health issues in the future.