Novel, Variant, and Pandemic Influenza (Avian and Swine)

There are four types of influenza viruses: A, B, C, and D. Influenza A and B viruses cause seasonal epidemics of disease in people (known as flu season) almost every winter in the United States. Influenza A viruses are the only influenza viruses known to cause flu pandemics (i.e., global epidemics of flu disease).

A novel influenza A virus is one that has caused human infection, but is different from current seasonal human influenza A viruses that circulate among people. Novel influenza viruses are usually influenza A viruses that circulate among animals. Human infections from influenza viruses circulating in birds and pigs are the most documented, though other animals could theoretically be the source of infection. Some novel influenza viruses are believed to pose a greater pandemic threat than others because they have caused serious human illness and death and also have been able to spread in a limited manner from person-to-person. CDC has tabulated the number of novel influenza infections in humans since the 2010-11 influenza season.

“Bird flu” is a non-scientific term that refers to a specific virus (H5N1) that has been present in domestic birds in Asia since 1997. It has caused outbreaks of disease in poultry throughout Southeast Asia, Africa, and Europe. Millions of birds have died or have been killed due to the disease. For more information please visit the Avian Influenza Information page. The New Mexico Department of Agriculture also has information on avian influenza in dairy cattle and poultry.

Since the beginning of 2012, CDC has noted an increase in the number of variant influenza infections associated with swine among humans. The majority of variant flu virus infections in the United States have occurred among people attending an agricultural fair where they were exposed to infected pigs or their contaminated environments. Agricultural fairs are large community events where people have the opportunity to show and sell animals, such as pigs, that they have raised. Large numbers of people and animals attend agricultural fairs. These settings provide an opportunity for people to come in close contact with pigs, some of which may be infected with influenza viruses, and their environment, which may become contaminated with influenza viruses when ill pigs cough or sneeze.

Pandemic Influenza

An influenza pandemic is a global outbreak of a new influenza A virus that is very different from current and recently circulating human seasonal influenza A viruses. Pandemics happen when new (novel) influenza A viruses emerge which are able to infect people easily and spread from person to person in an efficient and sustained way. Because the virus is new to humans, very few people will have immunity against the pandemic virus, and a vaccine might not be widely available. The new virus will make a lot of people sick. How sick people get will depend on the characteristics of the virus, whether or not people have any immunity to that virus, and the health and age of the person being infected.

Frequently Asked Questions

What’s the difference between a pandemic and a normal flu season?

Flu pandemics are rare and are caused by flu strains that are significantly different from those circulating in previous seasons. As a result, people have little to no immunity against the virus and many will become sick. While CDC has identified potential pandemic flu strains, stockpiles of vaccine are limited. Moreover, since the circulating strain my be different from the stockpiled vaccine, it may not be as effective. Pandemic strains often cause more serious disease. Because of this, past flu pandemics have led to high levels of illness, death, social disruption and economic loss.

Normal flu seasons involve flu strains that are similar to those of previous years. As a result, some people may have built up immunity, and there is also a vaccine developed for each year’s flu season. This allows standard control measures to contain the disease. Typically cases increase between October and May in the Northern Hemisphere, with a peak in cases usually occurring between December and February.

When is the next flu pandemic expected?

Three influenza pandemics occurred in the 20th century and one influenza pandemic occurred in the 21st century, all of which spread around the world within one year of being detected. Of these, the pandemic of 1918-1919 was the most severe, with 50 million or more deaths worldwide.

No one can predict when a pandemic might occur, but many scientists believe it is only a matter of time before the next one arises. Experts from around the world are watching the H5N1 Avian (bird) Flu situation in the Middle East, Europe and Asia very closely and are preparing for the possibility that the virus may begin to spread more easily and widely from person to person.

What is New Mexico doing to prepare for Pandemic Influenza?

In New Mexico, pandemic flu planning efforts have been underway for several years. A draft pandemic flu response plan was developed in 2007 and was updated in 2019 that gives New Mexico a template for dealing with this issue. Lessons learned from the COVID-19 pandemic will be incorporated in the next pandemic influenza plan.