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

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

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 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

OBJECTIVETo investigate the clinical features of severe acute respiratory syndrome (SARS).

METHODSForty-one medical care workers (aged 23 - 55 years, with a average of 32 years; men/women = 8/32) who were admitted to our hospital and diagnosed with SARS during March and April, 2003 were retrospectively analyzed.

RESULTSThirteen of all the patients were physicians and the rest were nurses. The disease was mainly transmitted through air droplet in a short distance, and overwork induced tiredness was involved in disease stimulation. Seventy-three percent of the patients presented fever as their first symptom. Ten patients complained inertia and myalgia. One patient showed no clinical symptoms, and bilateral infiltrates was found in his chest X-ray. Among the 41 cases, 6 (15%) were diagnosed as severe type. At the first week, the counts of white blood cells (WBCs), lymphocyte and platelets were (4.4 +/- 1.5) x 10(9)/L, 0.22 +/- 0.12 and (143 +/- 37) x 10(9)/L, which were significantly lower when compared with those at the 2nd to 4th week. Abnormal liver function was found in 27 cases (mostly with elevated serum ALT), with 70% occurred at the 3rd or 4th week. In terms of CT, 30 patients (73%) showed pathological changes in lungs, and bilateral lung involvement was found in 35.59%. Of 36 cases treated with steroids, 86% received middle or low dosage (80 - 240 mg/d). Artificial ventilation was used for twenty-seven patients, and air pipe mechanical ventilation was used for 1 case. Mortality in this study was 5%.

CONCLUSIONSInertia and myalgia may be the earlier symptoms of health care workers with SARS include, which are parallel to CT manifestations. There is no objective index for the assessment of the severity of the disease at early stage. The medicine associated toxicities may be the main reason of liver lesions. damages. Middle or low dosage of steroid was reasonable to be used as early as possible.

Adult ; Female ; Humans ; Infectious Disease Transmission, Patient-to-Professional ; Male ; Methylprednisolone ; therapeutic use ; Middle Aged ; Nurses ; Physicians ; Respiration, Artificial ; Retrospective Studies ; Severe Acute Respiratory Syndrome ; diagnosis ; therapy ; transmission