Although we are acquainted with the influenza A (H1N1) and types such as H5N1 or H3N2, there are other influenza variants that infect humans and cause us concern.

poultryResearchBlogging.orgThe influenza H7 comprises various lineages, H7N7, H7N3 and H7N2 are those who knowingly infect humans. Some lineages are not very pathogenic (LPAI) and others highly pathogenic (HPAI), the majority circulates in birds and several mammals, especially horses. In Canada in 2004 and in England in 2006, domestic bird breeders contracted the H7N3, and in 2007, the H7N2 also infected breeders. In all the cases, the flu had mild respiratory symptoms and conjunctivitis occurred in some victims. The conjunctivitis is not a common symptom in seasonal flu, which is contracted often.

However, the H7N7 caused more problems. In Holland in 2003, after the outbreak of H7N7 in domestic birds, 89 persons were confirmed having this virus. The respiratory symptoms were mild to moderate and again some developed conjunctivitis. One death by severe pneumonia and related symptoms was recorded. [1]

Other cases of H7N7 have already been recorded, all involving breeders. From ducks to a seal that sneezed on his caretaker, always with the concomitant occurrence of conjunctivitis. [2]

H9N2 is, however, restricted to birds, and its closest proximity with us is through poultry birds, especially ducks and turkeys. On March 1999, two children in Hong Kong were found with this virus and the symptoms were fever and irritation in the throat. Both cases were solved without complications some days later. Here, the pattern was recurrent, although the cases were in regions far from each other; in both situations the children reported having recent contact with poultry birds. [2]

In 2003 and later in 2007, this virus infected humans once again in Hong Kong. Again, two children. Both developed some flu symptoms and were cured. In the case of the 2003 virus, its genetic material showed the origin of the virus to be among poultry birds in the Hong Kong market. There are other recorded cases, all in the same region. [3]

Although the recorded cases of H9 and H7 are few, and with mild symptoms, these viruses are disturbing for being some of the few bird lineages transmitted to humans and between humans, with a potential to originate a highly pathogenic lineage directly or by the rearrangement with other types of Influenza A circulating in people.

A very disturbing characteristic of these cases is the frequency of contaminated breeders. After all, they are in direct contact with the animals, much more exposed than the majority of the people. In a recent study with over 2000 persons from various professions in China, 4.5% tested positive to anti H9 antibodies, indicating that they had been in contact with this lineage before. Among poultry bird sellers, the positive rate was much higher, at 15.5%. The response against H5 was also detected in 0.2% of the tested persons. [4]

This association with breeders and sellers shows the importance of monitoring the type of virus that can be contracted, as well as instructing them about the precautions to avoid infection and transmission to other people. In the case of H9N2, there is also the possibility of the production of vaccines for domestic animals, which should also help in protecting the owners.

Workers in constant contact with both domestic and wild animals can be an important link in the circulation and transmission of new lineages to humans.


[1] DEWIT, E., & FOUCHIER, R. (2008). Emerging influenza Journal of Clinical Virology, 41 (1), 1-6 DOI: 10.1016/j.jcv.2007.10.017
[2] Subbarao*, K., & Katz, J. (2000). Avian influenza viruses infecting humans Cellular and Molecular Life Sciences, 57 (12), 1770-1784 DOI: 10.1007/PL00000657
[3] Butt, K., Smith, G., Chen, H., Zhang, L., Leung, Y., Xu, K., Lim, W., Webster, R., Yuen, K., Peiris, J., & Guan, Y. (2005). Human Infection with an Avian H9N2 Influenza A Virus in Hong Kong in 2003 Journal of Clinical Microbiology, 43 (11), 5760-5767 DOI: 10.1128/JCM.43.11.5760-5767.2005
[4] Wang M, Fu CX, & Zheng BJ (2009). Antibodies against H5 and H9 avian influenza among poultry workers in China. The New England journal of medicine, 360 (24), 2583-4 PMID: 19516044