Severe acute respiratory syndrome – caused by one of the coronavirus group, see also MERS and COVID19. The virus probably originated in bats, then crossed into humans via masked palm civets.
The virus spread beyond its original outbreak in China when a businessman became unwell on his flight out of China and died in Vietnam in 2003. Further outbreaks appeared rapidly, as far afield as Toronto. Eventually led to 8000 cases globally, but rapid surveillance and isolation measured brought the epidemic to an abrupt end within 4 months.
Super shedders exist, who have much higher infectivity (1 case on a plane infected 120 others, whereas another plane had 4 cases on board, but no secondary cases occurred!). On the other hand, there is no documented transmission by asymptomatic cases, or between children.
Incubation period is 5-7 but up to 14 days. Spread is by respiratory, fomites, and faecal-oral routes. Peak shedding occurs at peak of clinical disease hence outbreaks were often among health care workers.
Symptoms are ‘flu-like, and non-specific. Fever is universal. Those who do badly have sudden deterioration on 10th day, with ARDS. Mortality is around 10%, but very age dependent, reaching over 50% in the over 65s. Children have lower viral loads, and generally have a benign course. Compared with adults, they perhaps get more gastrointestinal symptoms than respiratory.
Children under 5 yrs are hardly affected at all – perhaps because recent coronavirus infection protective, perhaps because of reduced immune reactivity.
No long term morbidity seen in children.
The diagnosis is suggested by the paucity of clinical signs (mild crepitations only, if anything) with an abnormal chest radiograph (non-specific), and laboratory evidence of leucopenia, lymphopenia, and thrombocytopenia. Raised AST/ALT also seen.
Definitive diagnosis is by ELISA or PCR, neither of which is very sensitive, or useful early on in disease.
Interferon alpha appears to be of benefit in vitro. Otherwise supportive.
Personal Protective Equipment effective if used properly – so buddy system.
Infection control – encourage self isolation, dedicated staff etc.