Sudden acute respiratory syndrome

Abstract

Emergence of new diseases Against this background, the emergence of new human infectious diseases or viruses is unsurprising. Severe acute respiratory syndrome was first recognised at the end of February in Hanoi, Vietnam.3 The agent is highly infectious, with attack rates of >50% among healthcare workers caring for patients with the syndrome.4 Preliminary data from the first cluster of about 60 probable cases in Hanoi indicate an incubation period of 5–9 days. The most common early systemic symptoms in Hong Kong and Hanoi include fever, malaise, myalgia, headache, and dizziness. Sore throat and rhinorrhoea occur early in fewer than 25% of cases, and cough occurred early in only 39% of cases.4 Because of its non-specific early manifestation, sudden acute respiratory syndrome will be overlooked unless clinicians have a high index of suspicion and seek a history of travel or contact with the syndrome. After 3–7 days of fever the lower respiratory phase begins, with a non-productive cough, which may be accompanied by dyspnoea and chest pain.5 Breathlessness requiring oxygen occurred in many cases after about five days and progressed to hypoxaemia requiring ventilatory support in around 15%, a rate similar to the 10-20% observed elsewhere.5 Early chest x ray findings typically show small focal unilateral diffuse interstitial infiltrates, which may be overlooked initially. The appearance evolves rapidly, often becoming more generalised and affecting both lung fields. Chest radiographs may, however, be normal during the febrile prodrome and throughout the illness.4 Lymphocytopenia is common and occasionally liver function values are raised.4 Clinical presentation suggests an illness of variable severity ranging from mild illness to death. The speculation is that the most severe illnesses occur among first level contacts of an index case. If real, this may reflect either repeated high dose exposure of the unsuspecting healthcare workers to the index case or attenuation of the pathogen during subsequent waves of infection.