WHO: Influenza at the human-animal interface

The World Health Organization (WHO) has published a document on the risk assessment of avian influenza at the human-animal interface. The document can be view and downloaded at the following address.

For each virus subtype the current situation has been described and following questions have been examined:

1. What is the likelihood that additional human cases of infection with avian influenza X viruses will occur?
2. What is the likelihood of human-to-human transmission of avian influenza X viruses?
3. What is the likelihood of international spread of avian influenza X viruses by travelers?

 

Avian influenza A(H5) viruses

Influenza A(H5) subtype viruses have the potential to infect humans and thus far, no human cases, other than those with influenza A(H5N1) and A(H5N6) viruses, have been reported to WHO.

In China influenza A(H5N6) viruses have been detected in poultry in the first half of 2017 and in one individual. Various influenza A(H5) subtypes continue to be detected in birds in Africa, Europe and Asia.

Question 1. Since the A(H5) viruses continue to be detected in animals and environments, further human cases can be expected.

Question 2. The likelihood of human-to-human transmission of A(H5) is low.

Question 3. Further community level spread is considered unlikely as evidence suggests that A(A5) viruses have not acquired the ability to transmit easily among humans.

 

Avian influenza A(H7N9) viruses

Since the last update on 30 October 2017, one new laboratory-confirmed human case of influenza virus infection was reported. Since 2013, a total of 1565 laboratory-confirmed cases of human infection, including at least 612 deaths, have been reported.

Question 1.Since the A(H7N9) virus continue to circulate in animals and environments, further human cases can be expected.

Question 2. This A(H7N9) virus has not acquired the ability of sustained transmission among humans, thus the likelihood is low.

Question 3. Further community level spread is considered unlikely as the A(H7N9) virus has not acquired the ability to transmit easily among humans.

 

Avian influenza A(H7N2) viruses

Since the last update on 30 October 2017, one laboratory-confirmed human case (a child from China and had been exposed to live poultry) of A(H7N2) virus infection was reported.

Question 1. Since the virus continues to be detected in poultry populations, further human cases can be expected.

Question 2. This virus has not acquired the ability of sustained transmission among humans, thus the likelihood is low.

Question 3. Further community level spread is considered unlikely as this virus has not acquired the ability to transmit easily among humans.

 

 

Swine Influenza Viruses

 

Influenza A(H1N1)v viruses

In 2017 one new laboratory-confirmed human infection with influenza A(H1N1)v viruses was detected in the state of Iowa in the United States (U.S). The adult person, prior to illness, had contact with swine. No human-to-human transmission was reported.

This virus and related swine influenza viruses have HA and NA gene segments derived from the seasonal human H1N1pdm09 virus that was likely introduced into swine in the USA by a recent reverse zoonosis.

Since 2015, 21 cases and one fatal case were reported to the U.S. Centers for Disease Control and Prevention.

 

Influenza A(H1N2)v viruses

Since the last update on 30/10/2017 one new laboratory-confirmed human infection with influenza A(H1N2)v viruses was detected in the state of Colorado in USA. The person, had contact with swine at an agricultural event prior to illness. Moreover, no human-to-human transmission was identified.

Since 2005, 13 cases were reported to CDC and 4 of these occurred in 2017.

 

Influenza A(H3N2)v viruses

Since the last update on 30/10/2017, two human infections with influenza A(H3N2)v were found in several states of USA. One case had contact with swine prior to illness, whereas the other cases had contact with one household member that did have exposure to swine.

Since 2005, 433 were reported to CDC and 61 of these occurred in 2017. One fatal case happened in 2012.

 

 

Risk assessment

 

Question 1. Since these viruses continue to be detected in swine populations in many regions of the world, further human cases can be expected.

Question 2. Although limited human-to-human transmission may have taken place, current evidence suggests that these viruses have not acquired the ability of sustained transmission among people, thus the likelihood is low.

Question 3. Further community level spread is considered unlikely as these viruses have not acquired the ability to transmit easily among humans.

 

Finally, the document report the overall risk management recommendations underlying the importance of the good food safety and hygiene practices, global surveillance and collaboration between the animal and human health sectors.

 

Further information can be found at the following address:

http://www.who.int/influenza/human_animal_interface/Influenza_Summary_IRA_HA_interface_12_07_2017.pdf?ua=1