Saturday, November 23, 2013

WHO: MERS in a Dozen Countries; Jump in Sporadic Cases

MERS confirmed and probable cases by month of onset and type (WHO)
The World Health Organization has issued an update on the MERS virus epidemic which is occurring in the middle east. (see .pdfCIDRAP summary)

WHO confirms that three new countries have reported infections with the Middle East Respiratory Syndrome virus, they include Spain, Kuwait and Oman.

MERS has been confirmed in a dozen countries so far. Six countries in the middle east have reported the virus, five in Europe and Tunisia in Northern Africa.

Previous infections have occurred in Jordan, Saudi Arabia, the United Arab Emirates (UAE) and Qatar in the Middle East and France, Germany, the United Kingdom (UK) and Italy in Europe. Two probable cases in India are awaiting official confirmation by health officials.

To date, WHO recognizes 179 cases worldwide, with 157 laboratory confirmed and another 19 considered 'probable'. Of those, 69 have died, or about 39%.

The death rate appears to have dropped a bit in the last two months, or since the last WHO summary update which was issued in September. At that time the mortality rate was about 45%. This 6% decline could be due to better reporting of less severe cases discovered through contact testing. The average age remained about the same, 51 years in this report versus 50 previously.

In September, researchers had expressed concern at the rise in sporadic cases which accounted for about a quarter of infections. Sporadic cases are those having no prior contact with an infected person or the first case within a cluster.

This reports shows there has been a sharp increase in the number of sporadic cases of the virus, According to the report, two thirds (67%) of new cases are now considered sporadic.

WHO researchers raised concerns about the spread to previously unaffected countries and the rise in sporadic cases. "This appearance of the virus in new countries and the steady increase in sporadic cases continues to raise concerns about possible expansion of virus in the as yet unknown reservoir."

A recent study published in The Lancet Infectious Disease calculated that there are five to ten undetected MERS cases for every reported case. They estimate there could be nearly a thousand symptomatic but unreported cases of the virus.

WHO confirms that many cases are going unreported due to MERS testing policies that only include victims who end up in hospital ICUs. According to the report:
"Countries in the affected area should strongly consider expanding testing to include community-acquired pneumonias that are admitted to hospital, even if they do not require mechanical ventilation or intensive care, especially if no alternate diagnosis explains the illness. Testing for MERS-CoV should be considered for incorporation into routine diagnostic algorithms for community-acquired pneumonias and not limited to severe cases in ICU."
Researchers are also concerned about the large numbers of infections which are occurring in medical facilities, either because the disease is not recognized or due to false-negative screening tests: 
"WHO has reports of a number of examples of laboratory confirmed MERS-CoV cases who initially tested negative from upper respiratory samples, while lower respiratory samples tested positive for MERS-CoV."
About 62% of secondary cases (49 confirmed, 11 probable) are believed to have been exposed in health care facilities. These represent health care workers, other patients and visitors. 

Exposure rates by country (WHO)
The study affirms previous research which suggests the virus is being sustained through human to human contact but also through an 'unknown reservoir' which continues to infect humans.

This unknown reservoir is suspected to be related to animals but the connection is still a mystery. The report noted the latest four victims in Qatar had all recently been exposed to farm animals.

Despite reports of the virus being found in camels and a genetic link to bats is suspected, neither are believed to be the source of infection in humans.  Most index and sporadic cases have had no contact with animals of any kind.

Intriguing clues to the origin of the virus continue to surface, but researchers caution that there are still important questions regarding the method of human exposure: 
"Specifically, the remaining questions include 1) the specific behaviors and exposures that bring humans into contact with sources of the virus, 2) whether camels are a part of the chain of transmission to humans or whether they are coincidentally infected, and 3) whether other animals may also play a role in transmission or act as a reservoir." 
WHO recommends that persons who have chronic illnesses use 'appropriate precautions' when visiting farm environments in the region. 

So far, only India has reported MERS in returning Hajj pilgrims, where two women who traveled together came down with the virus. Both have since recovered and official confirmation is still pending. 

WHO recommends that, "Countries outside of the affected region should maintain a high level of vigilance, especially those with large numbers of travellers or guest workers returning from the Middle East."

The report concludes with WHO's request that "Member States report all confirmed and probable cases along with information about their exposures, testing, and clinical course." and they "strongly recommend detailed case investigations for every case, case-control studies for index cases and intensive follow-up of contacts".

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