WHO Pandemic Warning Phases.Source [pdf].

What is a pandemic?

The World Health Organization (WHO) Emergency Committee declared on August 10 that we left the pandemic phase of the H1N1 virus. “The world is no longer in phase 6 of influenza pandemic alert. We are now moving into the post-pandemic period. The new H1N1 virus has largely run its course.” But, what does it mean?

WHO classifies the severity of an emergent disease in six global warning phases. As the majority of the emergent diseases are zoonosis, the warning levels are based on how much the pathogen is circulating among humans after the transmission. Between phases 1 and 3, the disease circulates specially among animals (in phase 1 it circulates only among humans), among domestic animals and some humans in phase 2, it is also
frequently transmitted among humans in phase 3. The classification varies according to the frequency which it goes into humans. Most of the potential diseases are in this phase, such as the yellow fever, although it contaminates people in forest regions, it is restricted especially to the wild cycle, i.e. animals.

The 4th phase describes a disease which already passed from animals to humans and circulates regardless those animals. An example of this situation is the occurrence of dengue in the summer, in which many tropical climate cities has dengue outbreaks in the rainy season.

Phases 5 and 6 describe an epidemic which is already spreading more than locally, during phase 5 there is an intense transmission, but restricted to the same place, and in phase 6 the transmission is global and the pandemic is in full development. These warning levels guide the monitoring and precautions the countries must take. It is advised to monitor borders and areas of intense circulation, as well as the supply of drugs and vaccines during phases 5 and 6.

Our current condition

When phase 6 is over, since great parte of the people was already infected or vaccinated, the decease still circulates, but not as severe as before. In the case of the flu, the out of season cases stop occurring and, as it already happened in other pandemics, the virus circulates annually instead of or simultaneously with the seasonal variants.

It is in this stage that the WHO considers we just entered. According to them, people already developed immunity in many locations, in addition to the good coverage of the vaccination. From the declaration “Out-of-season outbreaks are no longer being reported in either the northern or southern hemisphere. Influenza outbreaks, including those primarily caused by the H1N1 virus, show intensity similar to that seen during seasonal epidemics.

It is worth emphasizing that it does no mean that the H1N1 is gone. It still circulates and will probably enter the seasonal cycle common to the other variants, besides having gone back to the pigs and continue to rearrange. The committee highlights that “[...] this does not mean that the H1N1 virus has gone away. Based on experience with past pandemics, we expect the H1N1 virus to take on the behavior of a seasonal influenza virus and continue to circulate for some years to come.

The virus that was not cruel

Still in the committee’s declaration, one phrase calls the attention: “we have been aided by pure good luck. The virus did not mutate during the pandemic to a more lethal form. Widespread resistance to oseltamivir did not develop.” In fact, and luckily as it was said, there was no serious pandemic in 2009. The number
of patients and deceased were below the expectations, and part of that can be credited to the previous immunity of the elderly, which reduced the mortality among this risk population.

The severity of this pandemic was already questioned before, especially because the phase criteria adopted does not take into consideration the spreading disease severity. Even the seasonal flu can be classified as a pandemic during the winter of the Northern Hemisphere, if it were not by the lack of prevalence of a main variant.

Criticisms about the entrance of phase 6 warning were made in June, at the British Medical Journal. According to the critics, some people involved in the panel that decided to raise the level of pandemic warning had relevant conflicts of interest, since they received funding from vaccine manufacturers. The same manufacturers that signed contracts for the production of millions of doses distributed globally. The idea is that they raised the warning level unnecessarily in order to benefit the companies.

We can not forget that when a pandemic arises, there is little time to make decisions, and in most cases the consequences for excess of zeal are much smaller than by the lack of it. It is necessary to balance the warning created around this pandemic. At the same time it is necessary to have a previous and agile preparation to stop the outbreak and reduce its impact. The collaboration of the population is also essential to make this possible. Without the correct clarification of the situation, and the comprehension of the need of the measures to be taken, problems such as rumors about the H1N1 vaccine being unnecessary or even harmful tend to grow.