Germs: Bacteria, Viruses, Fungi, and Protozoa (for Teens)

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español: <a href="/es/teens/care-about-germs.html">Gérmenes: bacterias, virus, hongos y protozoos</a> </div> <div> <div id="reviewerBoxTop"> <div id="reviewedByTop"> Medically reviewed by: <a href="https://www.nemours.org/services/pediatric-emergency-medicine.html" target="_blank">Yamini Durani, MD</a> </div> </div> </div> <div> <div id="departmentSpecialty"> <a href="https://www.nemours.org/locations/primary-care.html" class="rev-multi" target="_blank">Learn About Primary Care Pediatrics at Nemours Children's Health</a> </div> </div> </div> <div id="khcontent"> <div id="khcontent_article" class="khLeft"> <span class="ISI_MESSAGE"></span> <ul id="msArticleControls"> <li class="ac-readspeaker"> <div class="rs_skip rs_skip_en rsbtn_kidshealth rs_preserve" id="readspeaker_button1"> <a onclick="rsUsed('1')" rel="nofollow" class="rsbtn_play rsen" title="Listen to this page using ReadSpeaker" 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class="rsbtn_btnlabel">Settings</span> </button> <button class="rsbtn_closer rsimg rspart rsbutton" title="Close Player" data-rsevent-id="rs_377229"> <span class="rsbtn_btnlabel">Close Player</span> </button> <span class="rsdefloat"></span> </span> </div> </div> </li> <li class="ac-textSize"> <div id="kh-text-sizer"> <button id="kh-text-sizer-largest" onclick="textSizer('3');"> <span class="hideOffScreen">Larger text size</span> </button> <button id="kh-text-sizer-larger" onclick="textSizer('2');"> <span class="hideOffScreen">Large text size</span> </button> <button id="kh-text-sizer-regular" onclick="textSizer('1');"> <span class="hideOffScreen">Regular text size</span> </button> </div> </li> <li class="ac-print"> <div id="kh-print-button"> <a onclick='printWindow1(this.href); return false; rel="nofollow"' tabindex="0"> <span class="printLabel">Print</span> </a> </div> </li> </ul>   <div> <div class="cmp-container"> <div class="rte-image">  <h3>What Are Germs?</h3> <p>The term "germs" refers to the microscopic bacteria, viruses, fungi, and protozoa that can cause disease.</p> <p><a href="/en/teens/handwashing.html">Washing hands</a> well and often is the best way to <a href="/en/teens/fighting-germs.html">prevent germs</a> from leading to infections and sickness.</p> <h4>Bacteria</h4> <p>Bacteria are tiny, single-celled organisms that get nutrients from their environments. </p> <p>Some <script type="text/javascript" id="splatJS_bacteria_T" name="splat" src="/content/kidshealth/us/en/teens/splats/bacteria.js"></script><script type="text/javascript" id="splatDW_bacteria_T">document.write(def_bacteria_T);</script> <noscript class="rs_skip"> bacteria</noscript>are good for our bodies — they help keep the <a href="/en/teens/digestive-system.html">digestive system</a> in working order and keep harmful bacteria from moving in. Some bacteria are used to make medicines and vaccines.</p> <p>But bacteria can cause trouble too, as with cavities, <a href="/en/teens/uti.html">urinary tract infections</a>, <a href="/en/teens/swimmers-ear.html">ear infections</a>, or <a href="/en/teens/strep-throat.html">strep throat</a>. Antibiotics are used to treat bacterial infections.</p> <h4>Viruses</h4> <p>Viruses are even smaller than bacteria. They aren't even a full cell. They are simply genetic material (DNA or RNA) packaged inside of a protein coating. They need to use another cell's structures to reproduce, which means they can't survive unless they're living inside something else (such as a person, animal, or plant).</p> <p>Viruses can only live for a very short time outside other living cells. For example, viruses in infected body fluids left on surfaces like a countertop or toilet seat can live there for a short time, but quickly die unless a live host comes along.</p> <p>Once they've moved into someone's body, though, viruses spread easily and can make a person sick. Viruses are responsible for some minor sicknesses like <a href="/en/teens/colds.html">colds</a>, common illnesses like the <a href="/en/teens/fight-flu.html">flu</a>, and very serious diseases like smallpox or <a href="/en/teens/std-hiv.html">HIV/AIDS</a>.</p> <p>Antibiotics are not effective against viruses. Antiviral medicines have been developed against a small, select group of viruses.</p> <h4>Fungi</h4> <p>Fungi (pronounced: FUN-guy) are multicelled, plant-like organisms. A fungus gets nutrition from plants, food, and animals in damp, warm environments.</p> <p>Many fungal infections, such as <a href="/en/teens/athletes-foot.html">athlete's foot</a> and <a href="/en/teens/yeast-infections.html">yeast infections</a>, are not dangerous in a healthy person. People who have weakened <a href="/en/teens/immune.html">immune systems</a> (from diseases like HIV or cancer), though, may develop more serious fungal infections.</p> <h4>Protozoa</h4> <p>Protozoa (pronounced: pro-toe-ZO-uh) are one-celled organisms, like bacteria. But they are bigger than bacteria and contain a nucleus and other cell structures, making them more similar to plant and animal cells.</p> <p>Protozoa love moisture, so intestinal infections and other diseases they cause, such as amebiasis and giardiasis, often spread through contaminated water. Some protozoa are parasites, which means that they need to live on or in another organism (like an animal or plant) to survive. For example, the protozoa that causes malaria grows inside red blood cells, eventually destroying them. Some protozoa are encapsulated in cysts, which help them live outside the human body and in harsh environments for long periods of time.</p> </div> </div> </div> <div id="reviewerBox"> <div id="reviewedBy"><strong>Medically reviewed by: </strong><a href="https://www.nemours.org/services/pediatric-emergency-medicine.html" class="vcard-link" target="_blank">Yamini Durani, MD</a> </div> <div id="reviewedDate">Date reviewed: July 2023</div> </div> <span class="ISI_MESSAGE">  </span> </div> <div id="khcontent_article_aside" class="khRight"> <div> <aside aria-labelledby="moreOnThisTopicHeader"> <div id="kh-mott-box"> <h2 id="moreOnThisTopicHeader" class="JSMott">More on this topic for:</h2> <ul id="kh-mott-tabs" role="tablist" class="JSMott"> <li data-section="teens" role="presentation"><button type="button" role="tab" aria-controls="teens_panel" id="teens_tab" tabindex="-1" aria-selected="false">Teens</button></li> </ul> <div id="teens_panel" role="tabpanel" aria-labelledby="teens_tab"> <h2 class="sansJSMott">More on this topic<br/>For Teens</h2> <ul id="kh-mott-teens-links" class="kh-mott-links"> <li> <a href="/en/teens/fighting-germs.html"> Fighting Germs </a> </li> <li> <a href="/en/teens/handwashing.html"> Hand Washing: Why It's So Important </a> </li> <li> <a href="/en/teens/center/flu-center.html"> Flu (Topic Center) </a> </li> <li> <a href="/en/teens/food-poisoning.html"> Food Poisoning </a> </li> <li> <a href="/en/teens/std.html"> STDs (Sexually Transmitted Diseases) </a> </li> <li> <a href="/en/teens/fight-flu.html"> 5 Ways to Fight the Flu </a> </li> <li> <a href="/en/teens/mrsa.html"> MRSA </a> </li> </ul> </div> <button id="kh-mott-toggle" data-expanded="false">View more</button> </div> </aside> </div> <aside aria-label="Nemours Message"> <div id="kh-partner-ad" class="rs_skip rs_preserve"> <div class="kh-inline"><iframe title="Partner Message" id="mobad_in_if" src="/content/kidshealth/us/misc/inline_ad.html" style="display: block; 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Germs: Bacteria, Viruses, Fungi, and Protozoa (for Teens) | Nemours KidsHealth