China ; epidemiology ; Humans ; Severe Acute Respiratory Syndrome ; epidemiology ; transmission

INTRODUCTIONIt has been noted that SARS transmission is characterised by a few super-spreading events (SSEs) giving rise to a disproportionate number of secondary cases. Clinical and environmental features surrounding the index cases involved were compared with cases in non- SSEs.

MATERIALS AND METHODSData on 231 cases of probable SARS admitted to Tan Tock Seng Hospital (TTSH) were used. Index cases directly causing 10 or more secondary cases were classified as having been involved in SSEs; all others were defined as non-SSEs.

RESULTSOnly 5 cases were involved in SSEs; all 5 were isolated on day 5 of illness or later, and spent at least a brief period in a non-isolation ward; in contrast, amongst the 226 non-SSE cases, only 40.7% and 4.0% were isolated late and admitted to non-isolation wards respectively, and only 3.1% had both these environmental features present; the differences were highly significant (P = 0.012, P <0.001 and P <0.001 by Fisher's Exact test). When compared to 7 non-SSE cases with delayed isolation and an admission to non-isolation wards, SSEs were more likely to have co-morbid disease or require ICU care at time of isolation (P = 0.045 for both factors).

CONCLUSIONSSEs were likely due to a conglomeration of environmental factors of delayed isolation and admission to a non-isolation ward, coupled with severe disease stage at time of isolation.

Adult ; Female ; Humans ; Male ; Middle Aged ; Severe Acute Respiratory Syndrome ; epidemiology ; transmission ; Singapore ; epidemiology

Betacoronavirus ; Coronavirus Infections ; epidemiology ; transmission ; Disease Outbreaks ; Humans ; Pandemics ; Pneumonia, Viral ; epidemiology ; transmission ; Severe Acute Respiratory Syndrome ; epidemiology

OBJECTIVETo explore the characteristics of severe acute respiratory syndrome (SARS) transmission in the population base on analyzing the first imported case and the chains of transmission.

METHODSFor the first imported SARS case and cases who were transmitted by the index case, epidemiological investigations were conducted using the guidelines for surveillance and case investigation issued by the Ministry of Health. Data as the date of onset of symptoms, date of hospitalization, contact history etc. for each of the cases and their close contacts were collected and analyzed.

RESULTSThe first imported SARS case introduced to Beijing had infected 9 people within the family and at the hospital, with two of whom died of the same disease. The incubation period for that index case was 4 days, and that for the cases considered to be the secondary and tertiary generations were 7 and 8 days, respectively. The shorter the incubation period, the longer the fever would last and clinically more severe.

CONCLUSIONOne of the epidemiological characteristics of SARS in Beijing was noticed that the disease clustered in families and hospitals. Infection through droplets and close contact has been viewed as the primary mode of transmission.

Adult ; China ; epidemiology ; Contact Tracing ; Cross Infection ; transmission ; Family Health ; Female ; Humans ; Infectious Disease Transmission, Patient-to-Professional ; Male ; Middle Aged ; Severe Acute Respiratory Syndrome ; epidemiology ; transmission

OBJECTIVEBy measuring airflow and ventilation distribution of ward building, to explore and verify the hypothesis of airborne transmission and risk factor of severe acute respiratory syndrome (SARS) nosocomial infection.

METHODSTracer gas (perfume of plant oil) was emitted to the bathroom of wards when SARS index patient lived. Six different experimental situations were designed to control the status of exhaust fan in bathrooms, exhaust fan in the top of building and fresh air exchange system. The concentration of perfume was separately measured by 4 groups of lab workers and recorded blindly by the scores of "tenth degree".

RESULTSTracer gas was detected from the wards of 8th to 13th floor.

CONCLUSIONArchitecture and ventilation system of the inpatient building in the hospital contributed to the aerodynamic condition of SARS nosocomial infection through airborne transmission. The distribution of tracer gas in the wards was associated with SARS patients in this building. It was possible that SARS could have been transmitted to for distance by aerosol or other carriers.

Air Microbiology ; China ; Cross Infection ; etiology ; Hospitals ; Humans ; SARS Virus ; isolation & purification ; Severe Acute Respiratory Syndrome ; transmission ; Ventilation

BACKGROUNDSevere acute respiratory syndrome (SARS) is characterized by both an atypical pneumonia and efficient nosocomial transmission. However, it remains unknown whether the infectivity and the virulence of the pathogen will change throughout the successive transmission. This study was conducted to compare the clinical features and management regimens of patients with SARS among the multiple generations from nosocomial transmission initiated by a super-spreader.

METHODSThe clinical data of 84 epidemiologically-linked SARS patients from a hospital outbreak were retrospectively studied. All patients, in whom a clear-cut transmission generation could be noted, had a direct or indirect exposure to the index patient and the epidemic successively propagated through the multiple generations of cases within a short period of time.

RESULTSThere were 66 women and 18 men with mean age of (29.2 +/- 10.3) years in this cluster; and 96.4% of whom were health care workers. Detailed contact tracing identified 35 (41.7%) first-generation cases, 34 (40.5%) second-generation cases, and 15 (17.8%) third-generation cases. No statistical differences among the multiple generations of transmission were found in terms of age, gender, incubation period and length of hospital stay. With the advanced transmission generations, the initial temperature lowered, the number of cases with dry cough decreased. There were no statistical differences in the peak temperature and duration of fever, other accompanying symptoms, leucopenia; however, the time from initial pulmonary infiltrates to radiographic recovery shortened (P < 0.05). No differences were found in maximum number of lung fields involved, duration from the onset of fever to the occurrence of pulmonary infiltrates and time from the initial pulmonary infiltrate to its peak among the multiple transmission generations (P > 0.05). No statistical differences were found in modes of oxygen therapy and sorts of antibiotics prescribed among the various transmission generations (P > 0.05); however, as with the advanced transmission generations, the number of cases prescribed with methylprednisolone, human gamma-globulin, interferon-alpha, antiviral drugs (oral ribavirin or oseltamivir) increased (P < 0.05) and time from admission to starting these medication shortened (P < 0.05).

CONCLUSIONSThere is no evidence that SARS infection will evolve or transmit within a fashion that permits it to become less powerful throughout the successive transmission within a short time.

Adult ; Contact Tracing ; Cross Infection ; physiopathology ; Female ; Humans ; Male ; Personnel, Hospital ; Retrospective Studies ; Severe Acute Respiratory Syndrome ; physiopathology ; transmission

OBJECTIVETo evaluate the infectivity of severe acute respiratory syndrome (SARS) during its incubation period by investigating chains of transmission and individuals isolated for medical observation with a view to providing scientific evidence for updating protocols of medical isolation.

METHODSIndividuals related with the two SARS chains of transmission in Beijing in 2003 and a group of individuals isolated for medical observation in Haidian district of Beijing during the SARS outbreak were selected as subjects of study. Contactors with SARS patients and those with symptom development following the contacts were investigated via questionnaire. Serum samples were collected from super transmitters and tested for SARS-CoV antibody by neutralization test and enzyme linked immunosorbent assay (ELISA).

RESULTSA total of 1112 contactors were investigated in three surveys. Of them, 669 had a history of close contact with symptomatic SARS patients, 101 developed symptoms with a rate of 15.1%, 363 had a history of close contact with patients in their incubation period, none of whom developed symptoms (0%). Serum samples were collected from 32 highly-exposed individuals, of whom 13 developing SARS symptoms after contact had serum samples positive for SARS-CoV antibody. Samples collected from the asymptomatic contactors were all negative for SARS-CoV antibody.

CONCLUSIONSARS cases are infectious only during their symptomatic period and are non-infectious during the incubation period. Isolation for medical observation should be placed for individuals who are in close contact with symptomatic SARS patients. The results of our study are of decisive significance for the Ministry of Health to the definition of SARS close contactor.

China ; epidemiology ; Disease Outbreaks ; Humans ; Infectious Disease Incubation Period ; SARS Virus ; physiology ; Severe Acute Respiratory Syndrome ; epidemiology ; transmission ; virology

OBJECTIVETo study the transmission route of severe acute respiratory syndrome (SARS) nosocomial infection.

METHODSTen identified SARS patients were selected from a general hospital in March. Survey was carried out through a standardized questionnaire provided by Chinese Center for Disease Control and Prevention. Contents of the questionnaire would include: history of contact with SARS patient, route of infection, methods used for protection and so on.

RESULTS(1) Distribution os SARS patients were confined to 3 wards: 4, 5, and 6 on the 7, 8, 12, 13 and 14 floors in the west unit of the inpatient building. Most of the inpatients were elderly and having severe original diseases. (2) Index patients were the first generation source of transmission and they infected inpatients and medical staff, making them the second generation. People with latent infection who had close contact with SARS patients might also serve as the possible source of transmission. (3) The major transmission routes were: near distant droplet infection and close contact infection. There was also a clue to the probability of aerosol or droplet nuclei infection through air-conditioning and ventilation system.

CONCLUSIONNosocomial infection appeared to be the main characteristic of the SARS epidemic in the early stage of this hospital. Other than close contact and near space airborne transmission of SARS virus, the possibility of long-distance aerosol transmission called for further epidemiological and experimental studies in the future.

Adult ; Aged ; China ; Contact Tracing ; Cross Infection ; transmission ; Female ; Hospitals, General ; Humans ; Male ; Middle Aged ; Severe Acute Respiratory Syndrome ; transmission ; Surveys and Questionnaires

OBJECTIVESTo investigate the transmission process of severe acute respiratory syndrome (SARS) and to evaluate the infectiveness of SARS patients in different periods of disease epidemics.

METHODSStandardized questionnaire was used to conduct case investigation and contact tracing by combining the field investigation and telephone interview. Transmission process, infectivity, transmission chain and contact history of SARS were studied through data analyses.

RESULTSOn 25th March 2003, a 91 year old man was admitted to Hospital J in Beijing with stroke and fever. He died on 30th March. From 31st March, there was an outbreak of SARS among his contacts in the family and in the hospital he was admitted to. Contacts would include his relatives, other co-patients and health care workers in the Hospital J. Chinese Field Epidemiology Training Program trainees conducted an investigation of the outbreak. Among the 207 contacts of the index cases through different generations, there were 36 cases of SARS (attack rate 17%) patients with one death. There were 12 cases having directly contact with the index case and 13 cases with one secondary case. The transmission chains of this outbreak could clearly be depicted. All the cases had close contacts during the symptomatic period of their index patients. Among the relatives, 85% of the cases had 3 - 5-day contact with their index patients after the onset of the illnesses. There was no significant difference between the two attack rates-70% for whose who had contact with the patient before and after illness onset) and 67% for those who only had contact after the onset of the illness. Out of the 44 social acquaintances and 38 of the family members who had contacts with the index patients during the incubation period, no one was found ill. Among the close contacts at the hospital who had no protection when providing care to the patient, the attack rate was found over 80%.

CONCLUSIONSAll the secondary cases of this outbreak had a history of direct and close contacts to the index patients after the onset of the illness. There was no evidence indicating that SARS cases were infectious during their incubation period.

Aged ; Aged, 80 and over ; China ; epidemiology ; Humans ; Infectious Disease Transmission, Patient-to-Professional ; Male ; Severe Acute Respiratory Syndrome ; epidemiology ; prevention & control ; transmission

BACKGROUNDTo find out the timing of serologic responses after illness onset and distribution of IgG antibody to SARS-CoV in SARS cases of transmission chain or non-transmission chain.

METHODSThe IgG and IgM antibodies to SARS-CoV were tested by indirect ELISA in serum samples from 301 clinically diagnosed SARS cases.

RESULTSTotally 158 SARS cases were involved in 15 chains of transmission. The positive rates of SARS-CoV IgG in those chains were 85.70%-100.00% and the overall rate was 94.30% (149/158). The chain of transmission could spread to four generations, but the SARS cases were reduced with increase of generations. There was no significant difference among positive rates of SARS-CoV IgG for generations, Chi square=5.11, P greater than 0.05. The positive rate of SARS-CoV IgG in cases who were not in chain of transmission was 12.59%(18/143) which was statistically significantly different from that of cases in chain of transmission, Chi square=199.64, P less than 0.001. During days 0-7,8-14,15-21,22-30 after onset, the cumulated positive rate of SARS-CoV IgG was 16.67%, 40.00%, 70.00% and 93.10%, respectively, then was kept at the level above 90% and lasted for 217 days. The cumulated positive rate of SARS-CoV IgM during days 0-7 after onset was the same to that of IgG. During days 8-14, 55.17% of cases had seroconversion for IgM which reached a peak (86.96%) during days 21-30. Then the rate rapidly declined.

CONCLUSIONMore than 94% of cases with SARS could produce IgG antibody when they were infected by SARS-CoV. Detecting SARS-CoV IgG could provide a diagnostic evidence for case confirmation. SARS-CoV IgG appeared as early as 7 days after onset and reached the peak at about weeks 4. Then the high rate of antibody was maintained for more than 6 months.

Antibodies, Viral ; blood ; Disease Transmission, Infectious ; Enzyme-Linked Immunosorbent Assay ; Humans ; Immunoglobulin G ; blood ; Immunoglobulin M ; blood ; SARS Virus ; immunology ; Severe Acute Respiratory Syndrome ; immunology ; transmission