How Do You Know if the Flu Is Killing You

"Did you become your influenza shot?" If your friends are anything like mine, you lot heard this question at to the lowest degree a dozen times before Thanksgiving. You lot probably got your fair share of disdainful looks besides, if you answered "No." But why are nosotros worried about getting the flu shot now and not in May? Why is there a influenza season at all? After all, what does a virus living in a host who provides a undecayed, cozy incubation chamber of 98°F, care whether it is freezing and snowy outside or warm and sunny? This question has bothered people for a long time, but only recently have we begun to empathize the reply.

What is the Influenza?

In lodge to discuss why we take a influenza flavor, we must first understand what the influenza is. The flu, likewise chosen flu, is a viral respiratory affliction. A virus is a microscopic infectious amanuensis that invades the cells of your torso and makes you sick. The flu is often confused with some other virus, the cold, because of the similarity in symptoms, which can include a coughing, sore throat, and stuffy nose. However, flu symptoms too include fever, cold sweats, aches throughout the body, headache, exhaustion, and even some gastro-intestinal symptoms, such as vomiting and diarrhea (1).

The flu is highly contagious. Adults are able to spread the virus one day prior to the appearance of symptoms and up to seven days afterwards symptoms begin. Influenza is typically spread via the coughs and sneezes of an infected person (i). Around 200,000 people in the United states of america are hospitalized each year because of the influenza, and of these people, about 36,000 die.  The flu is most serious for the elderly, the very young, or people who take a weakened immune system (1).

The Influenza Season

The flu flavor in the U.S. can brainstorm as early on equally October, but usually does not become into full swing until December. The season generally reaches its summit in February and ends in March (2). In the southern hemisphere, however, where winter comes during our summer months, the influenza season falls betwixt June and September. In other words, wherever there is winter, at that place is flu (3). In fact, fifty-fifty its proper noun, "influenza" may be a reference to its original Italian name, influenza di freddo, meaning "influence of the cold" (4).

A common misconception is that the flu is caused past cold temperatures. However, the flu virus is necessary to have the flu, so common cold temperatures can only exist a contributing cistron. In fact, some people have argued that it is not common cold temperatures that brand the flu more common in the winter. Rather, they attest that the lack of sunlight or the different lifestyles people lead in winter months are the primary contributing factors. Hither are the near popular theories almost why the influenza strikes in wintertime:

1) During the wintertime, people spend more time indoors with the windows sealed, so they are more than likely to breathe the same air every bit someone who has the flu and thus contract the virus (3).

2) Days are shorter during the wintertime, and lack of sunlight leads to  low levels of vitamin D and melatonin, both of which crave sunlight for their generation. This compromises our immune systems, which in turn decreases ability to fight the virus (iii).

iii) The influenza virus may survive meliorate in colder, drier climates, and therefore be able to infect more people (iii).

The Influenza Likes Cold, Dry Weather condition

For many years, information technology was impossible to test these hypotheses, since nigh lab animals do non catch the flu like humans do, and using humans as exam subjects for this sort of thing is generally frowned upon. Effectually 2007, nevertheless, a researcher named Dr. Peter Palese plant a peculiar comment in an onetime newspaper published after the 1918 flu pandemic: the author of the 1919 paper stated that upon the arrival of the flu virus to Army camp Cody in New Mexico, the guinea pigs in the lab began to get sick and die (four). Palese tried infecting a few republic of guinea pigs with flu, and certain plenty, the guinea pigs got sick. Importantly, non only did the guinea pigs showroom flu symptoms when they were inoculated by Palese, simply the virus was transmitted from one guinea squealer to some other (iv).

Now that Palese had a model organism, he was able to begin experiments to become to the lesser of the influenza season. He decided to start test whether or non the flu is transmitted meliorate in a cold, dry climate than a warm, humid one. To test this, Palese infected batches of guinea pigs and placed them in cages adjacent to uninfected guinea pigs to allow the virus to spread from 1 cage to the other. The pairs of guinea squealer cages were kept at varying temperatures (41°F, 68°F, and 86°F) and humidity (twenty%-fourscore%). Palese institute that the virus was transmitted improve at depression temperatures and low humidity than at loftier temperatures and loftier humidity (encounter Figure one).

Figure 1 ~ Experimental Setup. Guinea pigs were housed in adjacent cages. Republic of guinea pigs in cage i were infected past Palese with influenza. Palese observed how many guinea pigs in cage 2 became infected from the guinea pigs in muzzle 1 at different temperatures and levels of humidity. B, C) Manual rates were 100% at low humidity, regardless of temperature. At high humidity, transmission occurred only at the lower temperature.

Notwithstanding, Palese's initial experiment did not explain why the virus was transmitted best at libation temperatures and low humidity. Palese tested the immune systems of the animals to find out if the allowed system functions poorly at depression temperatures and depression humidity, simply he establish no difference in innate amnesty amidst the republic of guinea pigs (5). A paper from the 1960s may provide an alternate explanation. The study tested the survival time of dissimilar viruses (i.e. the corporeality of time the virus remains feasible and capable of causing disease) at contrasting temperatures and levels of humidity. The results from the study suggest that influenza actually survives longer at low humidity and low temperatures. At 43°F with very low humidity, most of the virus was able to survive more than 23 hours, whereas at high humidity and a temperature of 90°F, survival was diminished at even i 60 minutes into incubation (3).

The information from these studies are supported by a third written report that reports higher numbers of influenza infections the month after a very dry period (6). In case you're wondering, this is only the instance in places that experience winter. In warmer climates, oddly enough, influenza infection rates are correlated most closely with high humidity and lots of rain (6). Unfortunately, not much research has been washed to explain these contradictory results, then information technology'southward unclear why the influenza behaves so differently in disparate environments. This emphasizes the need for continued influenza research. Therefore, we tin can conclude that, at least in regions that have a wintertime season, the influenza virus survives longer in cold, dry out air, so it has a greater gamble of infecting another person.

Although other factors probably contribute equally well, the principal reason we take a flu flavour may simply exist that the influenza virus is happier in cold, dry weather and thus better able to invade our bodies. Then, as the temperature and humidity proceed dropping, your best bet for warding off this nasty bug is to go your flu shot ASAP, stay warm, and invest in a humidifier.

Hannah Foster is a PhD candidate in the Molecules, Cells, and Organisms program at Harvard University.

For more than information virtually the influenza, check out this video:

References

1) Medical News Today. What is flu? What is influenza? What are the symptoms of influenza? < >[2 November, 2014]

2) Centers for Illness Control. The Influenza Season. <http://www.cdc.gov/flu/about/season/flu-season.htm> [2 November, 2014]

3) Elert, E. 2013. FYI: Why is There a Winter Flu Flavor? Popular Science.  <http://www.popsci.com/scientific discipline/commodity/2013-01/fyi-why-winter-flu-season> [2 November, 2014]

4) Kolata, G. 2007. Study Shows Why the Flu Likes Wintertime. New York Times. <http://www.nytimes.com/2007/12/05/health/research/05flu.html?_r=1&> [2 Nov, 2014]

5) Lowen, A.C., S. Mubareka, J. Steel, and P. Palese. 2007. Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature. PLOS Pathogens. 3(10):e151.

half dozen) Roos, R. 2013. Study: Influenza likes weather cold and dry out or humid and rainy. University of Minnesota Center for Infectious Disease Research and Policy. <http://world wide web.cidrap.umn.edu/news-perspective/2013/03/report-flu-likes-weather-common cold-and-dry-or-boiling-and-rainy> [14 Nov, 2014]

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Source: https://sitn.hms.harvard.edu/flash/2014/the-reason-for-the-season-why-flu-strikes-in-winter/

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