An investigative team of infectious disease experts who traveled to Saudi Arabia during an outbreak of the Middle East respiratory syndrome coronavirus reports that the virus poses a serious risk to hospitals because it is easily transmitted in health care settings.
The team, from Johns Hopkins and elsewhere, investigated the spread of the virus, called MERS CoV, in four Saudi hospitals in May and concluded that it is even more deadly than the related coronavirus responsible for the 2003 outbreak in Toronto of severe acute respiratory syndrome, or SARS, which the team also investigated. At the time of the Saudi Arabia investigation, 23 people were infected with MERS, and 11 had died of the SARS-like virus. Saudi health officials now put the death toll at 32, with another 49 infected.
The experts, whose report on the outbreak was published in The New England Journal of Medicine online June 19, say that MERS is easily transmitted not only from patient to patient but also through the transfer of sick patients to other hospitals. Team member Trish Perl, senior hospital epidemiologist for Johns Hopkins Medicine and a professor at the Johns Hopkins University School of Medicine, says that swift action by local health officials to monitor the situation and spread of the disease, supported by rapid detection, isolation, and treatment of those infected, has helped stem the outbreak. Also, hospital staff tightened infection control procedures, introducing more rigorous cleaning procedures with stronger disinfectants, and treating infected patients in private rooms while wearing masks, gowns, and gloves, and masking noninfected patients who are nearby.
Saudi health officials invited Perl and fellow infectious disease specialists Connie Price, from the University of Colorado at Denver, and Allison McGeer, from the University of Toronto, to assist the country with its investigation. Greeting the team on arrival was a dolly full of cartons of medical records, which team members reviewed in their hotel rooms. Additional data and blood samples collected after visits to all four hospitals were later shared with colleagues at the Johns Hopkins Bloomberg School of Public Health and experts in viral genetics at the Wellcome Trust Sanger Institute in the United Kingdom.
Among the team's major findings was that MERS, even with relatively fewer people infected than in the SARS outbreak, had a death rate many times higher than SARS', at 48 percent and 8 percent, respectively. However, experts say that the MERS death rate may come down if more cases are identified, including among patients with mild symptoms.
The time from viral exposure to the first signs of symptoms of coughing, shortness of breath, fever, or vomiting was 5.2 days; it took on average 7.6 days for the virus to spread from one person to the next.
Among the 23 initially infected, five were family members and two were health care workers: a nurse who had worked with other nurses caring for infected patients and an ICU physician who had cared for and been directly exposed to MERS patients. Nine infected patients had received dialysis treatment at the same hospital, some at the same time. Another dialysis patient had been transferred between units at different hospitals, where others became infected. Eight other infected patients were transferred between facilities, which the research team believes led to additional exposures.
"The story of how this outbreak occurred and how this virus was transmitted became very clear once we started to lay out the evidence," says Perl.
"Our investigation showed some surprising similarities between MERS and SARS. Both are very deadly viruses and easily transferred between people, and even between health care facilities," says Perl, who adds that some people, such as the original MERS dialysis patient, also inexplicably appeared to transmit the infection faster than others. SARS has a similar history.
Epidemiologist and investigative team member Derek Cummings, an associate professor at the Bloomberg School, says that knowing the MERS incubation and generation times is critical to halting future outbreaks because "it tells us how long we have to act" before someone exposed to the virus starts to show symptoms and when people they infect also start to show symptoms.
Perl points out that intense monitoring leads to early detection of those infected, which can then lead to immediate isolation (to protect others from becoming infected) and treatment. No cure exists for MERS, but infected people can be supported on mechanical ventilation, if needed, to help them breathe, or offered fluids to lower fever. Perl says that early detection makes a difference; among those who were diagnosed while already ill and in the hospital, three out of four died, while only three out of 19 died among those who were diagnosed early after admission to a hospital.
A rapid test to detect MERS is the next priority in containing future outbreaks, Perl says, noting that medical experts also must determine what precautions are most important in preventing its spread, and what screening criteria need to be in place to prevent outbreaks from hospital-to-hospital patient transfers.
