New estimates suggest that a third of H7N9 patients admitted to hospital have died

June 23, 2013, Lancet

A group of researchers at the Chinese Center for Disease Control and Prevention, in Beijing, China and The University of Hong Kong, analysed data on hospital admissions related to H7N9, as well as using surveillance data to estimate the risk of fatality for patients who had been admitted to hospital and the risk of fatality in symptomatic cases.

The results suggest that H7N9 has a lower fatality risk than H5N1, another which emerged in 2003, but a higher fatality risk than the 2009 H1N1 . H5N1 had a fatality risk of around 60% for patients admitted to hospital, whereas pandemic H1N1 killed 21% of patients with the virus who were admitted to hospital.

Using data from China's sentinel surveillance network, and based on assumptions of how many people are likely to seek health care after becoming infected, the researchers suggest that between 0,16% and 2,8% of all people with symptomatic H7N9 infection are at risk of dying. The wide interval between these estimates reflects the difficulties of accurately measuring how many people are infected with H7N9 but experience only mild symptoms.

According to the authors, "Assessing the severity profile of is vitally important in the management and treatment of any infectious disease outbreak. Although previous clinical case series have focused on the potential for avian influenza H7N9 to cause severe illness, we have estimated that mild cases might have occurred. Our results thus support continued vigilance and sustained intensive control efforts against the virus to minimise risk of human infection, which is greater than previously recognised."

In a second Article, published at the same time, the same group of researchers at the Chinese , in Beijing, China and the University of Hong Kong compare the epidemiological characteristics of H7N9 and the older H5N1 viruses, warning that and need to be prepared for the possibility that H7N9 will reappear later this year.

For both viruses, men seem to have been more susceptible to infection, particularly in urban areas, suggesting that one of the main risk factors for infection in both cases is the handling of infected poultry. The researchers also outline some striking differences between infections caused by the two viruses, including more rapid disease progression seen with H5N1 infections, accompanied by a greatly increased risk of dying for patients admitted to hospital, nearly double that for H7N9.

The incubation period of H7N9 was estimated at 3•3 days on average, lower than previous estimates, and directly informing quarantine policies.

According to the authors, "The warm season has now begun in China, and only one new laboratory-confirmed case of H7N9 in human beings has been identified since May 8, 2013. If H7N9 follows a similar pattern to H5N1, the epidemic could reappear in the autumn. This potential lull should be an opportunity for discussion of definitive preventive public health measures, optimisation of clinical management, and capacity building in the region in view of the possibility that H7N9 could spread beyond China's borders."

The research reported in the two papers is part of a broad, ongoing collaborative effort between the Chinese Center for Disease Control and Prevention and the University of Hong Kong's School of Public Health to define the epidemiology of influenza A (H7N9) in real time.

Explore further: Study reveals new details about H7N9 influenza infections that suddenly appeared in China

More information: Severity estimates: … 0140-6736(13)61207-6 /abstract
H7N9 & H5N1 comparison: … (13)61207-6/abstract

Related Stories

Study reveals new details about H7N9 influenza infections that suddenly appeared in China

June 19, 2013
(Medical Xpress)—Researchers with the Network Dynamics and Simulation Science Laboratory at the Virginia Bioinformatics Institute have revealed new information about the latest strain of type A influenza, known as H7N9, ...

The risks of H7N9 infection mapped

May 3, 2013
A map of avian influenza (H7N9) risk is presented in Biomed Central's open access journal Infectious Diseases of Poverty today. The map is comprised of bird migration patterns, and adding in estimations of poultry production ...

Only 14 China H7N9 patients left in hospital

June 10, 2013
Only 14 patients from China's H7N9 bird flu outbreak are still in hospital, national health authorities said in their latest update on the disease.

Evidence of host adaptation of avian-origin influenza A virus

May 15, 2013
The connection between human avian-origin influenza A (H7N9) virus infection and environmental sources of the virus were determined based on clinical data, epidemiology, and virological characteristics of the three early ...

Most with confirmed H7N9 avian flu are critically ill

April 25, 2013
(HealthDay)—Most Chinese patients with confirmed avian influenza A (H7N9) are critically ill and 21 percent have died, according to a preliminary report published online April 24 in the New England Journal of Medicine.

Ferrets, pigs susceptible to H7N9 avian influenza virus

May 23, 2013
Chinese and U.S. scientists have used virus isolated from a person who died from H7N9 avian influenza infection to determine whether the virus could infect and be transmitted between ferrets. Ferrets are often used as a mammalian ...

Recommended for you

New approach could help curtail hospitalizations due to influenza infection

January 18, 2018
More than 700,000 Americans were hospitalized due to illnesses associated with the seasonal flu during the 2014-15 flu season, according to federal estimates. A radical new approach to vaccine development at UCLA may help ...

Certain flu virus mutations may compensate for fitness costs of other mutations

January 18, 2018
Seasonal flu viruses continually undergo mutations that help them evade the human immune system, but some of these mutations can reduce a virus's potency. According to new research published in PLOS Pathogens, certain mutations ...

Flu may be spread just by breathing, new study shows; coughing and sneezing not required

January 18, 2018
It is easier to spread the influenza virus (flu) than previously thought, according to a new University of Maryland-led study released today. People commonly believe that they can catch the flu by exposure to droplets from ...

Zika virus damages placenta, which may explain malformed babies

January 18, 2018
Though the Zika virus is widely known for a recent outbreak that caused children to be born with microencephaly, or having a small head, and other malformations, scientists have struggled to explain how the virus affects ...

New study validates clotting risk factors in chronic kidney disease

January 17, 2018
In late 2017, researchers from Boston University School of Medicine (BUSM) discovered and published (Science Translational Medicine, (9) 417, Nov 2017) a potential treatment target to prevent chronic kidney disease (CKD) ...

Fresh approach to tuberculosis vaccine offers better protection

January 17, 2018
A unique platform that resulted in a promising HIV vaccine has also led to a new, highly effective vaccine against tuberculosis that is moving toward testing in humans.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.