Swine Influenza A(H1N1)

Case definitions for infections with swine influenza A(H1N1) Virus

In order to understand the spectrum of severity of the disease caused by swine influenza A(H1N1) virus infection , the clinical case description includes both mild form of influenza‐like illness (ILI) and more severe forms (lower respiratory tract infections including pneumonia and severe acute respiratory illness (SARI)). In addition, asymptomatic laboratory‐confirmed infections should be reported.

The following case definitions are for the purpose of reporting probable and confirmed cases of swine influenza A(H1N1) virus infection to WHO.

Clinical case description

Acute febrile respiratory illness (fever >38°C ) with the spectrum of disease from influenza‐like illness to pneumonia.

A Confirmed case of swine influenza A(H1N1) virus infection is defined as an individual with laboratory confirmed swine influenza A(H1N1) virus infection by one or more of the following tests*:
• real‐time RT‐PCR
• viral culture
• four‐fold rise in swine influenza A(H1N1) virus specific neutralizing antibodies.

A Probable case of swine influenza A(H1N1) virus infection is defined as an individual
with an influenza test that is positive for influenza A, but is unsubtypable by reagents used to detect seasonal influenza virus infection OR

A individual with a clinically compatible illness or who died of an unexplained acute
respiratory illness who is considered to be epidemiologically linked to a probable or
confirmed case.

* Note: The test(s) should be performed according to the most currently available guidance on testing (http://www.who.int/csr/disease/swineflu/en/index.html).

Source:
Interim WHO guidance for the surveillance of human infection with swine influenza A(H1N1) virus. 27 April 2009

Swine influenza - update 3

27 April 2009 -- The current situation regarding the outbreak of swine influenza A(H1N1) is evolving rapidly. As of 27 April 2009, the United States Government has reported 40 laboratory confirmed human cases of swine influenza A(H1N1), with no deaths. Mexico has reported 26 confirmed human cases of infection with the same virus, including seven deaths. Canada has reported six cases, with no deaths, while Spain has reported one case, with no deaths.

Further information on the situation will be available on the WHO website on a regular basis.

WHO advises no restriction of regular travel or closure of borders. It is considered prudent for people who are ill to delay international travel and for people developing symptoms following international travel to seek medical attention, in line with guidance from national authorities.

There is also no risk of infection from this virus from consumption of well-cooked pork and pork products. Individuals are advised to wash hands thoroughly with soap and water on a regular basis and should seek medical attention if they develop any symptoms of influenza-like illness.

source:
http://www.who.int/csr/don/2009_04_27/en/index.html

Current WHO phase of pandemic alert

Current phase of alert in the WHO global influenza preparedness plan

In the 2009 revision of the phase descriptions, WHO has retained the use of a six-phased approach for easy incorporation of new recommendations and approaches into existing national preparedness and response plans. The grouping and description of pandemic phases have been revised to make them easier to understand, more precise, and based upon observable phenomena. Phases 1–3 correlate with preparedness, including capacity development and response planning activities, while Phases 4–6 clearly signal the need for response and mitigation efforts. Furthermore, periods after the first pandemic wave are elaborated to facilitate post pandemic recovery activities.

The current WHO phase of pandemic alert is 4.

In nature, influenza viruses circulate continuously among animals, especially birds. Even though such viruses might theoretically develop into pandemic viruses, in Phase 1 no viruses circulating among animals have been reported to cause infections in humans.

In Phase 2 an animal influenza virus circulating among domesticated or wild animals is known to have caused infection in humans, and is therefore considered a potential pandemic threat.

In Phase 3, an animal or human-animal influenza reassortant virus has caused sporadic cases or small clusters of disease in people, but has not resulted in human-to-human transmission sufficient to sustain community-level outbreaks. Limited human-to-human transmission may occur under some circumstances, for example, when there is close contact between an infected person and an unprotected caregiver. However, limited transmission under such restricted circumstances does not indicate that the virus has gained the level of transmissibility among humans necessary to cause a pandemic.

Phase 4 is characterized by verified human-to-human transmission of an animal or human-animal influenza reassortant virus able to cause “community-level outbreaks.” The ability to cause sustained disease outbreaks in a community marks a significant upwards shift in the risk for a pandemic. Any country that suspects or has verified such an event should urgently consult with WHO so that the situation can be jointly assessed and a decision made by the affected country if implementation of a rapid pandemic containment operation is warranted. Phase 4 indicates a significant increase in risk of a pandemic but does not necessarily mean that a pandemic is a forgone conclusion.

Phase 5 is characterized by human-to-human spread of the virus into at least two countries in one WHO region. While most countries will not be affected at this stage, the declaration of Phase 5 is a strong signal that a pandemic is imminent and that the time to finalize the organization, communication, and implementation of the planned mitigation measures is short.

Phase 6, the pandemic phase, is characterized by community level outbreaks in at least one other country in a different WHO region in addition to the criteria defined in Phase 5. Designation of this phase will indicate that a global pandemic is under way.

During the post-peak period, pandemic disease levels in most countries with adequate surveillance will have dropped below peak observed levels. The post-peak period signifies that pandemic activity appears to be decreasing; however, it is uncertain if additional waves will occur and countries will need to be prepared for a second wave.

Previous pandemics have been characterized by waves of activity spread over months. Once the level of disease activity drops, a critical communications task will be to balance this information with the possibility of another wave. Pandemic waves can be separated by months and an immediate “at-ease” signal may be premature.

In the post-pandemic period, influenza disease activity will have returned to levels normally seen for seasonal influenza. It is expected that the pandemic virus will behave as a seasonal influenza A virus. At this stage, it is important to maintain surveillance and update pandemic preparedness and response plans accordingly. An intensive phase of recovery and evaluation may be required. an animal influenza virus circulating among domesticated or wild animals is known to have caused infection in humans, and is therefore considered a potential pandemic threat.

Source:
http://www.who.int/csr/disease/avian_influenza/phase/en/index.html