WHO: H5 Flu Viruses Most Obvious Health Threat
The agency posted an update titled "warning signals from the volatile world of influenza viruses." It said the world is better prepared for an influenza pandemic.
Saying the current global influenza situation "is characterized by a number of trends that must be closely monitored," the World Health Organization's latest update includes warnings about animal influenza viruses co-circulating and exchanging genetic material, giving rise to novel strains; continuing cases of human H7N9 infections in China; a recent spurt of human H5N1 cases in Egypt; and changes in the H3N2 seasonal influenza viruses that have affected the protection conferred by the current vaccine.
"The highly pathogenic H5N1 avian influenza virus, which has been causing poultry outbreaks in Asia almost continuously since 2003 and is now endemic in several countries, remains the animal influenza virus of greatest concern for human health. From end-2003 through January 2015, 777 laboratory-confirmed human cases of H5N1 virus infection have been reported to WHO from 16 countries. Of these cases, 428 (55.1%) have been fatal," according to the update. "Over the past two years, H5N1 has been joined by newly detected H5N2, H5N3, H5N6, and H5N8 strains, all of which are currently circulating in different parts of the world. In China, H5N1, H5N2, H5N6, and H5N8 are currently co-circulating in birds together with H7N9 and H9N2.
The H9N2 virus has been an important addition to this mix, as it served as the 'donor' of internal genes for the H5N1 and H7N9 viruses. Over the past four months, two human infections with H9N2 occurred in China. Both infections were mild and the patients fully recovered. Virologists interpret the recent proliferation of emerging viruses as a sign that co-circulating influenza viruses are rapidly exchanging genetic material to form novel strains. Viruses of the H5 subtype have shown a strong ability to contribute to these so-called 'reassortment' events."
"The emergence of so many novel viruses has created a diverse virus gene pool made especially volatile by the propensity of H5 and H9N2 viruses to exchange genes with other viruses. The consequences for animal and human health are unpredictable yet potentially ominous," it states.
It says H5 and H7 viruses are of greatest concern because they can rapidly mutate from a form that causes mild symptoms in birds to one that causes severe illness and death in poultry populations.
The most promising part of the update is its section on global flu pandemic preparedness, which is better than ever before, WHO reports, adding that during 2014, the 142 laboratories in 112 countries in the WHO Global Influenza Surveillance and Response System tested more than 1.9 million clinical specimens, helping to keep a close eye on influenza viruses.