Sunday, February 2, 2014

Status of the Influenza A(H7N9) virus, World Health Organization, January 31, 2014

The World Health Organization (WHO) is an arm of the United Nations and is tasked with monitoring international public health. One of the most important roles of this public health organization is to identify and track novel infectious diseases. MERS-CoV and Influenza A(H7N9) are two recent novel infectious diseases that WHO has been monitoring and tracking recently.

On January 31, 2014, The WHO published a summary of what is known about H7N9 infections, reservoirs, clinical presentation, protection, treatment, and recommendations.
WHO report: Background and summary of human infection with avian influenza A(H7N9) virus – as of 31 January 2014

This the first background and summary provided by WHO on H7N9 infections since April 3, 2013 (link). The report summarizes what is known about H7N9 at this time. It is important to understand that WHO provides factual information about the status of H7N9 cases and the disease as it is understood on the day of the report. WHO does not generally provide forecasts or speculate on the pandemic potential for a specific disease such as H7N9.

Here is a brief digest of the WHO report.

H7N9 is infecting individuals over a wide geographic area in eastern China and Taiwan. So far there is no evidence of sustained human to human transmission. WHO does not address the issue of several small family clusters that may represent human-to-human transmission.

The reservoir for the virus has not yet been formally identified but is likely avian in origin. Symptoms of H7N9 are nonspecific, such as fever, cough, and shortness of breath, all of which could be signs of a number of different respiratory infections. Laboratory testing is necessary to confirm H7N9 infection. As with other novel influenza infections, H7N9 seems to respond to treatment with neuraminidase inhibitors. Given early in the infection stage neuraminidase inhibitors can reduce disease severity and possibly increase chances of survival.

Males are infected about twice the rate of females. Although WHO indicates that the case fatality ratio (CFR) is .22 through January 28, 2014, the CFR for infected cases is uncertain because many recent confirmed cases are still hospitalized. Most of the severe reported cases are elderly individuals with chronic conditions. The median age of the cases that have died is 66 years old.

Although H7N9 vaccines are in development, none are currently available in the event of a pandemic outbreak. WHO continues to recommend a variety of prevention and control measures including hand hygiene and use of personal protective equipment (PPE) when in contact with a confirmed patient. As with any acute respiratory infection, droplet protection and the use of PPE including eye protection are recommended. Although aerosolized human-to-human transmission has not been confirmed, proper precautions to avoid aerosolized droplets is also recommended.

In the report WHO provides a number of specific recommendations for public health officials, researchers, clinicians, and laboratory personnel. WHO does not recommend any international screening or travel or trade restrictions  be applied for  H7N9 at this time. 


In summary, the lack of an identified host and the wide geographic distributions of cases suggests that H7N9 will not burn itself out soon. The fact that a few mild and asymptomatic cases have been reported provides some hope that a portion of the population has some innate or acquired immunity. H7N9 has now become another emerging infectious disease that has the potential to cause a pandemic. 

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