H7N9 Pandemic threat

Human infections with a new avian influenza A (H7N9) virus continue to be reported in China. The virus has been detected in poultry in China as well. While mild illness in human cases has been seen, most patients have had severe respiratory illness and some people have died. The only case identified outside of China […]

What is pandemic influenza

Influenza viruses are changing continuously and new strains emerge from time to time. If a new influenza virus subtype, that is very different from all previous viruses, emerges and causes disease in the human population, people will have little or no specific immunity to it, and consequently this virus may spread quickly and become a […]


In the past, new strains have generated pandemics causing high death rates and major disruptions to society. Although healthcare has improved in recent decades, epidemiological models project that today a pandemic is likely to result in 2 to 7.4 million deaths globally. In developed countries alone, accounting for 15% of the world’s population, models project […]

Pandemic alert phases

The World Health Organization (WHO) has developed an alert system to help inform the world about the development of the different stages towards a pandemic. The alert system is comprised of six phases. The current situation with the HPAI-H5N1 virus in animals and humans places the world in pandemic alert phase 3. This means that […]

How do pandemics Occur

An influenza pandemic is a global outbreak of influenza and occurs when a new influenza virus emerges, spreads and causes disease worldwide. Influenza A viruses continuously undergo antigenic evolution. There are two main mechanisms by which they do so: antigenic drift causes regular influenza epidemics, while antigenic shift is the cause of occasional global outbreaks […]

Human-to-human flu virus transmission

How are influenza viruses transmited from human to human? Seasonal and pandemic influenza are highly contagious diseases and are spread primarily by coughing and sneezing. When they sneeze, people release tiny droplets of fluid into the air. Those tiny droplets can fly up to 1 metre and infect persons nearby by reaching susceptible cells of […]

Hosts of H5N1

Wild birds are the natural hosts of influenza A viruses. In principle, all subtypes of influenza A viruses can be found in them. Typically, little or no disease is caused by infection of wild birds with these avian influenza viruses, which are therefore called low pathogenic avian influenza (LPAI) viruses. However, when LPAI viruses of […]