Outbreak of human infections with avian influenza A(H7N9) virus

Since 31 March 2013, the government of China has been notifying to the World Health Organization (WHO) about human infections with the avian influenza A(H7N9) virus. While human infections with other subgroups of H7 influenza viruses such as H7N2, H7N3, and H7N7 have previously been reported, the current event in China is the first one that A(H7N9) viruses have been detected among humans and the first time that a low pathogenic avian influenza virus is being associated with human fatalities.

An assessment of the clinical, epidemiological and virological data from reported cases is key to learn and understand the source of exposure, way of transmission and both animal-to-human and human-to-human routes of transmission. Information and evidence produced from data analysis are valuable for supporting efforts to control the outbreak and avoiding further human fatalities.

In order to support and encourage analysis of available data and dissemination of information from the outbreak of human infections with avian influenza A(H7N9) virus, I've created the bellow exploratory dashboard using officially reported data from WHO.

Current situation of the outbreak

As of 29 April 2013, the laboratory confirmed cases has risen to 126 including 24 deaths for a case fatality rate of 19%, according to the World Health Organization’s official count. Based on date of symptom onset of laboratory-confirmed cases, the index case is from Shanghai with date onset 19 February, 2013. China southeaster provinces of Zhejjiang, Shanghai and Jiangsu have the higher number of cases, being Shanghai the province with the higher number of deaths (12 deaths). A high proportion of cases, about 60% are hospitalized under treatment.

From 19 February to 7 march the case fatality rate was 100% as the first three cases dead, that is started decreasing with peak of 68.7% on 28 march that was follow by a decreasing trend till 17 April with a value of 20.5% Since then, CFR has remained steady between the ranges of 23.8% – 19.1%.

The age and sex distribution of cases shows that number of cases is higher in males in every age group and 55% of cases are 65 and over years old. Fatality cases is significantly high (62.5%) in the group of 65 and over years old compared to other age groups.

Up today, four provinces have fatality cases, with CFR values of 35.3% in Shanghai, 25% in Anhui, 19.2% in Jiangsu and 13% in Zhejiang.

There is still limited information about the scope of the disease the virus causes and about the source of exposure. The disease is of public health concern because most patients have been severely ill. There is no indication thus far that it can be transmitted between people, but both animal-to-human and human-to-human routes of transmission are being actively investigated.

Conclusions

Spatio-temporal, age and sex distributions of cases may help to detect important changes in the epidemiology of this virus and get a better understanding of the situation, high-risk populations, targeted interventions, prevention and control measures (e.g. vaccination) and treatment options (e.g. antivirals) may be identified.

Data visualizations and dashboards such as that included in this article can play an important role for monitoring and exploring data, generate actionable information and disseminate key messages to health professionals and managers, decision makers and the general public.

Additional information