Singapore SARS-Free For 66 Days And Clear Of Any Smoldering Cases

16 Jul 2003

The last probable SARS case in Singapore was isolated on 11 May 2003. Since then, 66 days have passed with no new probable SARS cases. Intensified surveillance has been maintained throughout this period.

Intensified surveillance to flush out any smoldering cases

The second Toronto SARS outbreak, 8 days after Toronto was first removed from the World Health Organisation's (WHO) list of countries with recent local transmission of SARS, highlighted the possibility of undetected atypical SARS cases triggering off a fresh outbreak of SARS.

As a precautionary measure, the Ministry of Health (MOH) embarked on an intensive surveillance exercise to ensure that there were no unidentified SARS cases. The exercise focused on three groups who were likely to present a higher risk, namely;

(i) patients who were in Tan Tock Seng Hospital (TTSH) and Singapore General Hospital (SGH), and in the affected ward in the National University Hospital (NUH), during the periods when the respective hospitals had SARS cases;
(ii) residents of nursing homes; 
(iii) suspect SARS patients.

Patients at TTSH, SGH and NUH

TTSH, SGH and NUH conducted reviews of patients who had been in hospital at the time there were active SARS cases. The review by SGH involved all patients who had been hospitalised in SGH during the "hot period" of the SGH Ward 57 and 58 outbreak. NUH conducted reviews on patients who were hospitalised in the same ward as patients who were later diagnosed to have SARS. TTSH has largely completed the review of the patients discharged from its "at-risk" wards since 1 March 2003. In total, the outcomes of nearly 10,000 patients from these three hospitals were traced.

Since 15 April, inpatients from TTSH and SGH who had chronic medical conditions were discharged with a 10-day home quarantine order, even if they were not known to have been exposed to SARS. At the end of the quarantine period, they were recalled to their respective hospital for a review. Other patients who did not have any chronic conditions were placed on phone surveillance for 14 days on discharge.

During the review, patients discharged on home quarantine orders or phone surveillance were traced to determine their status at the end of the home quarantine or phone surveillance period. Patients discharged to nursing homes were traced to ensure that they had gone through a "washout period" of isolation for 10 days before being admitted to the general wards of nursing homes. Patients who had not returned to the hospital for a review were contacted by telephone to determine their status.

The review of all these cases from TTSH, SGH and NUH did not turn up any suspected SARS cases.

Residents at nursing homes

Several measures had already been implemented to improve the SARS-preparedness level of Nursing homes. The free movement of patients between hospitals and nursing homes was controlled so as to reduce the risk of infection being spread between institutions. Training in infection control was provided to all step-down care providers. MOH assisted nursing homes to set up contingency plans on the steps that they should take if they have any cases suspected to have SARS. MOH also conducted audits of the SARS precautionary measures at the step-down facilities.

In late May, a fever surveillance system was implemented in all nursing homes, which require nursing homes to report to MOH when three or more residents and/or healthcare workers in the same ward are down with fever. MOH conducted on-site investigations of all fever clusters notified. MOH doctors also visited all the nursing homes to assess whether the fever surveillance was being carried out effectively

Despite this intensive surveillance, no suspected SARS cases were detected.

Patients previously admitted as suspect SARS cases

During the initial phase of the global SARS outbreak, diagnostic laboratory tests were not available as the causative agent for SARS had not yet been identified. Therefore, probable and suspect SARS cases were classified according to the WHO's SARS case definition which did not depend on laboratory testing.

When the SARS coronavirus (SARS-CoV) was subsequently identified as the causative agent, diagnostic laboratory tests to detect the virus (PCR or Polymerase Chain Reaction) and the antibodies to the virus (serology) were developed. With the availability of these diagnostic tests, the WHO case definition for probable SARS was revised on 1 May 2003 to include laboratory diagnosis as a criteria for defining a probable SARS case. Hence suspect cases which are laboratory test positive for coronavirus would be classified as probable cases.

When locally validated PCR and serology tests for coronavirus became available in Singapore on 5 April 2003 and 2 May 2003 respectively, these tests were carried out for all patients admitted for probable and suspect SARS, as well as cases which were being observed for SARS.

MOH conducted a review of all the suspect SARS cases admitted to TTSH since 1 March 2003 taking into account their serology and culture results for the SARS coronavirus. The review could only be concluded in early July 2003 as serial samples were required for the serology testing. This is because the antibody test may take up to 28 days after the onset of illness to become positive.

As at 15 July 2003, there have been about 600 patients who were admitted as suspect SARS cases. Among these, there were 32 suspect SARS cases who tested positive for SARS antibodies or had positive culture for coronavirus. A further 700 observation for SARS cases were also tested and were all negative. The 32 suspect SARS cases who were positive for SARS antibodies had been admitted to TTSH in March or April 2003. They had been isolated during their illness and had been discharged upon their recovery and after being afebrile for at least 48 hours.

Upon discharge, 10 had been placed on home quarantine orders, while the remaining 21 had been discharged on home medical leave for a period of 14 days. One case died in hospital.

There are no public health concerns based on the detailed review of these 32 cases. In line with WHO's guidelines, MOH will be reclassifying these suspect cases as probable cases solely on the basis of the positive test results which have been recently obtained. Hence the total number of probable SARS cases will be 238 cases. It is emphasised that all these cases had been previously identified and isolated as suspect cases in March or April 2003. Singapore has remained SARS free for 66 days since the last probable SARS case was isolated on 11 May 03.

Situation Update

Since the last MOH update on 9 July 2003, the last remaining probable SARS patient in TTSH has recovered from SARS. She is a 67 Chinese lady admitted to TTSH on 14 April 2003. She was in intensive care from 15 April to 10 July 2003. She was discharged from the SARS Ward on 13 July 2003. She remains in TTSH for the management of her chronic medical conditions.

New suspect case

There were no new suspect cases admitted to TTSH.

New observation cases

From 9 to 16 July 2003, a total of 7 cases were admitted to TTSH for observation. Of these, 5 have been diagnosed as non-SARS cases.

Quarantine Figures* (As of 16 July)

The quarantine figures are as follows:

#Discharged patients under home quarantine = 7

Contacts under home quarantine = 0

Total under home quarantine orders = 7

*Quarantine cases refer to those who are required to stay at home for precautionary reasons as they may have had contact with a SARS patient. These are healthy individuals.

# This is an added precautionary measure for discharged SARS patients as well as those with co-morbidities.

Summary of SARS Cases

A summary of SARS cases is as follows:

Recovered from SARS: 205

Hospitalised: nil

Deaths: 33

Probable cases: 238

Suspect cases: 0

Observation cases: 2