Wednesday, 7 January 2015

Plague debrief: what really happened in the July 2014 Gansu case of pneumonic plague?

by Michael Woodhead
In July 2014 a case of pneumonic plague was widely reported in the media.

The victim was a 38-year old shepherd who caught the infection from a marmot (the usual carriers of the infection) after it was caught by his dog. At the time it was widely reported that the town of Yumen (near Jiayuguan) where he was treated, had been put into lockdown. None of the 30,000 residents were allowed to leave town and more than 150 close contacts were kept under observation in quarantine. It looks like Chinese authorities did the right thing - but only after a fatal delay in the initial diagnosis. A new report published by the local infection control team gives more details of the case.

Dr Ge Pengfei and colleagues say that the man contracted the Yersinia pestis infection from an infected marmot after it was caught by his dog on 11 July. He skinned the marmot for its pelt and fed the meat to his dogs. Two days later the shepherd started to develop respiratory symptoms and went into a nearby village to seek treatment. However, when he first went to the local clinic on 15 July he was mis-diagnosed as having a simple respiratory tract infection and given just a prescription for an antibiotic (clindamycin) and some anti-inflammatories. When his condition worsened later that day he was seen by doctors at the hospital in Yuman, who diagnosed pneumonia on x-ray and they gave him an ineffective antibiotic, cefoperazone, and more anti-inflammatory treatment.

It was only later that night when the man's condition deteriorated further and he started coughing up blood that throat swabs were taken, which showed the presence of the characteristic Yersinia bacilli when tested. Doctors then gave the man the recommended treatment of IV streptomycin, but this was too late and probably did more harm than good in the rapidly advancing conditions of the infection. Streptomycin must be used with great care in advanced plague because it cases the Y. pestis bacteria to burst (lysis) and release large amounts of the endotoxin that causes septic shock. This is what happened in the case of the Gansu shepherd, whose quickly deteriorated in the early hours of 16 July and he died at 5am.

The infection control team said they also detected Yersinia infection in the man's sister in law and in two patients who had been in close contact with him at the hospital. These people were among the 150 close contacts subject to quarantine and to preventive treatment with streptomycin. This containment strategy worked, as none of the close contacts developed full blown pneumonic plague.

The infection control team said them man may have survived if his infection has been detected earlier. However, the village clinic and hospital had only limited medical facilities, and the plague was only picked up when cultures were examined under a microscope.

They said that local clinics in areas such as Gansu where plague is present (on average there is one case per year in the region) should be alert for the early signs of the infection - and be prepared to take a careful history to see if there has been any contact with potential sources such as marmots and infected dogs. Despite the death of the patient, they said the incident had shown that quarantine and antibiotic prophylaxis procedures for contacts were effective.

"Doctors need to improve awareness and ask about contact history for the possibility of plague infection to avoid misdiagnosis," they recommended.

International Journal of Infectious Diseases.

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