Bacteria and Viruses (2023)

Bacteria and viruses are the most common cause of food poisoning. The symptoms and severity of food poisoning vary, depending on which bacteria or virus has contaminated the food.

To prevent illness, always follow the food safety steps: clean, separate, cook, and chill. Other prevention tips for specific bacteria and viruses are included below.

The bacteria and viruses that cause the most illnesses, hospitalizations, or deaths in the United States are described below and include:

(Video) Bacteria and viruses - What is the difference between bacteria and viruses?

  • Campylobacter
  • Clostridium perfringens
  • E. coli
  • Listeria
  • Norovirus
  • Salmonella

Other important bacteria and viruses that cause foodborne illness include:

  • Bacillus cereus
  • Botulism
  • Hepatitis A
  • Shigella
  • Staphylococcus aureus (Staphylococcal [Staph] Food Poisoning)
  • Vibrio Species Causing Vibriosis

Bacillus cereus

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SourcesA variety of foods, particularly rice and leftovers, as well as sauces, soups, and other prepared foods that have sat out too long at room temperature.
Incubation period
  • Diarrheal: 6-15 hours
  • Emetic (vomiting): 30 minutes to 6 hours
  • Diarrheal: Watery diarrhea and abdominal cramps
  • Emetic (vomiting): Nausea and vomiting
Duration of illness24 hours
What to doDrink plenty of fluids and get rest. If you cannot drink enough fluids to prevent dehydration, call your doctor.
  • If food is to be stored longer than two hours, keep hot foods hot (over 140°F) and cold foods cold (40°F or under)
  • Store cooked food in a wide, shallow container and refrigerate as soon as possible.


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  • Infants: Honeyand products containing honey, such as infant pacifiers filled with or dipped in honey.
  • Infants, children and adults:Improperly home-canned or preserved foods, including low-acid vegetables and fermented fish; improperly canned commercial foods; herb-infused oils, baked potatoes in aluminum foil, cheese sauce, bottled garlic.
Incubation period
  • Infants: 3-30 days
  • Children and adults: 18-36 hours
  • Infants: Lethargy, poor feeding, constipation, weak crying, poor muscle tone (appear "floppy").
  • Children and adults: Double vision, blurred vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth, and muscle weakness.
Duration of illnessVariable
What to doBotulism is a medical emergency.If you have symptoms of botulism, see your doctor or go to the emergency room immediately.


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(Video) Viruses vs. Bacteria | What's The Difference?

SourcesUnpasteurized (raw) milk, chicken, shellfish, turkey, contaminated water.
Incubation period2 to 5 days
SymptomsDiarrhea, cramps, fever, and vomiting; diarrhea may be bloody.
Duration of illnessAbout one week
What to do

Drink plenty of fluids and get rest. If you cannot drink enough fluids to prevent dehydration or if your symptoms are severe, call your doctor.

Antibiotics are recommended only for patients who are very ill or are more likely to develop a serious illness, such as people with weakened immune systems.

  • Drink pasteurized milk. Do not drink raw milk.
  • Do not drink untreated water.

Clostridium perfringens

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SourcesBeef, poultry, gravies,food left for long periods in steam tables or at room temperature, and time and/or temperature abused foods.
Incubation period6 to 24 hours
SymptomsDiarrhea and stomach cramps (no fever or vomiting),
Duration of illnessLess than 24 hours. In severe cases, symptoms may last for 1-2 weeks.
What to doDrink plenty of fluids and get rest. If you cannot drink enough fluids to prevent dehydration, call your doctor.
  • Thoroughly cook foods, particularly meat, poultry, and gravies, to a safe internal temperature.
  • Use a food thermometer to make sure.
  • Keep food hot after cooking (at 140˚ F or above) and serve meat dishes hot, within 2 hours after cooking.
  • Microwave leftovers thoroughly (to 165˚F or above).
  • Refrigerate leftovers within two hours of preparation (at 40˚F or below).
  • Divide large amounts of food, such as roasts or big pots of chili or stew, into shallow containers and refrigerate immediately. It is OK to put hot foods directly in the refrigerator.

E. coli

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  • Contaminated food, especially undercooked ground beef, unpasteurized (raw) milk and juice, soft cheeses made from raw milk, and raw fruits and vegetables (such as lettuce, other leafy greens, and sprouts).
  • Contaminated water, including drinking untreated water and swimming in contaminated water.
  • Animals and their environment, particularly cows, sheep, and goats.
  • Feces of infected people.
Incubation period3 to 4 days for most people, can be 1 to 10 days
  • Severe diarrhea that is often bloody, severe stomach pain, and vomiting. Usually little or no fever is present.
  • Symptoms of hemolytic uremic syndrome (HUS) include decreased urine production, dark or tea-colored urine, and losing pink color in cheeks and inside the lower eyelids.
Duration of illness5 to 10 days. Most people will be better in 5 to 7 days. If HUS develops, it usually occurs after about 1 week.
What to doDrink plenty of fluids and get rest. If you cannot drink enough fluids to prevent dehydration or if your symptoms are severe (including bloody diarrhea or severe stomach pain), call your doctor.
  • Avoid eating high-risk foods, especially undercooked ground beef, unpasteurized milk or juice, soft cheeses made from unpasteurized milk, or sprouts.
  • Use a food thermometer to make sure that ground beef has reached a safe internal temperature of 160° F.
  • Wash hands before, during, and after preparing food, after diapering infants, and after contact with cows, sheep, or goats, their food or treats, or their living environment.

Hepatitis A

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(Video) Pathways: Bacteria vs. Viruses: What's the Difference?

SourcesRaw or undercooked shellfish from contaminated waters, raw produce, contaminated drinking water, uncooked foods, and cooked foods that are not reheated after contact with an infected food handler.
Incubation period28 days average (ranges from 15 to 50 days)
SymptomsDiarrhea, darkurine or light-colored stools, jaundice, fever, fatigue, nausea, joint pain, stomach pain, upset stomach, and loss of appetite.
Duration of illnessSymptoms usually last less than 2 months, although some people can be ill for as long as 6 months.
What to doSee your doctor if you have signs or symptoms of hepatitis A or think you may have been exposed to the virus.
  • Avoid eating raw oysters or other raw or undercooked shellfish.
  • Washhands frequently with soap and running water for at least 20 seconds, particularly after using the bathroom, after changing diapers, and before, during, and after preparing food.
  • Vaccination is the best way to prevent hepatitis A. Hepatitis A vaccination is recommended for:
    • All children at age 1 year
    • People with direct contact with others who have hepatitis A
    • People with chronic or long-term liver disease
    • People with clotting-factor disorders
    • Travelers to countries where hepatitis A is common
    • Men who have sexual encounters with other men
    • People who use or inject drugs
    • People experiencing homelessness


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  • Unpasteurized (raw) milk and dairy products.
  • Soft cheese made with unpasteurized milk, such as queso fresco, feta, Brie, Camembert.
  • Raw fruits and vegetables (such as sprouts).
  • Ready-to-eat deli meats and hot dogs.
  • Refrigerated pâtés or meat spreads.
  • Refrigerated smoked seafood.
Incubation periodUsually 1 to 4 weeks, can be as long as 70 days
SymptomsListeria can cause fever and diarrhea similar to other foodborne germs, but this type of Listeria infection is rarely diagnosed.

Symptoms in people with invasive listeriosis, meaning the bacteria has spread beyond the gut, include:

  • For pregnant women: fever, fatigue and muscle aches. Pregnant women may also have no symptoms but experience fetal death, pre-term labor, or infection of the newborn.
  • For all others, stiff neck, confusion, loss of balance, and convulsions in addition to fever and muscle aches.
Duration of illnessDays to weeks
Who is at risk
  • Adults age 65 and older
  • Pregnant women and their newborns
  • People whose immune systems are weakened due to illness or medical treatment
What to doFor invasive listeriosis, antibiotics given promptly can cure the infection. In pregnant women, antibiotics are given to prevent infection in the unborn baby.

Recommendations for everyone:

  • Do not drink raw (unpasteurized) milk, and do not eat soft cheeses made with it, such as queso fresco.
  • Eat cut melon right away or refrigerate it.

Recommendations for people at higher risk:

  • People at higher risk should not eat the following foods:
    • Refrigerated pâtés or meat spreads from a deli or meat counter or from the refrigerated section of a store
    • Hot dogs, cold cuts, and deli meats, unless they are heated to an internal temperature of 165°F or until steaming hot before eating.
    • Refrigerated smoked seafood, unless it is canned or shelf-stable or it is in a cooked dish, such as a casserole
    • Raw or lightly cooked sprouts of any kind
    • Soft cheese, such as queso fresco, queso blanco, panela, brief, Camembert, blue-veined, or feta, unless labeled as made with pasteurized milk
  • Be aware that Hispanic-style cheeses made from pasteurized milk, such as queso fresco, have caused Listeria infections, most likely because they were contaminated during cheese-making. Safer choices, especially for pregnant women, include cream cheese, mozzarella, and hard cheeses.


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Produce, shellfish, ready-to-eat foods touched by infected food workers (salads, sandwiches, ice, cookies, fruit), or any other foods contaminated with particles of vomit or feces from an infected person.

Incubation period12 to 48 hours
SymptomsDiarrhea, vomiting, nausea, and stomach pain. Diarrhea tends to be watery and non-bloody. Diarrhea is more common in adults and vomiting is more common in children.
Duration of illness1 to 3 days. Among young children, older adults, and hospitalized patients, it can last 4 to 6 days.
What to doDrink plenty of fluids and get rest. If you cannot drink enough fluids to prevent dehydration, call your doctor.
  • Wash hands frequently with soap and running water for at least 20 seconds, particularly after using the bathroom and before, during, and after preparing food.
  • If you work in a restaurant or deli, avoid bare-hand contact with ready-to-eat foods.
  • Clean and disinfect surfaces contaminated by vomit or diarrhea (use a bleach-based household cleaner as directed on the label). Clean and disinfect food preparation equipment and surfaces.
  • If you are ill with diarrhea or vomiting and for two days afterwards, do not cook, prepare, or serve food for others.
  • Wash fruits and vegetables and cook oysters and other shellfish thoroughly before eating them.
  • Wash clothing or linens soiled by vomit or fecal matter immediately. Remove the items carefully to avoid spreading the virus. Machine wash and dry.


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(Video) Good Germs vs. Bad Germs


Food:A variety of foods have been linked to Salmonella, including vegetables, chicken, pork, fruits, nuts, eggs, beef and sprouts.

Animals and their environments:Particularly reptiles (snakes, turtles, lizards), amphibians (frogs), birds (baby chicks) and pet food and treats.

Incubation period6 hours to 6 days
SymptomsDiarrhea, fever, stomach cramps, vomiting
Duration of illness4 to 7 days
What to do

Drink plenty of fluids and get rest. If you cannot drink enough fluids to prevent dehydration or if your symptoms are severe, call your doctor.

Antibiotics are recommended only for patients who have a serious illness (such as severe diarrhea, high fever, or bloodstream infection), or are more likely to develop a severe illness or complications (infants, adults over 65 years old, and people with weakened immune systems).

  • Avoid eating high-risk foods, including raw or lightly cooked eggs, undercooked ground beef or poultry, and unpasteurized (raw) milk.
  • Wash your hands after contact with animals, their food or treats, or their living environment.


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SourcesContact with an infected person or consumption of contaminated food or water. Shigella foodborne outbreaks are most often associated with contamination by a sick food handler.
Incubation period1 to 7 days (usually 1 to 2 days)
SymptomsSudden stomach cramping, fever, diarrhea that may be bloody or contains mucus, nausea, and feeling the need to pass stool even when the bowels are empty.
Duration of illness5 to 7 days
Who's at risk?Children, especially toddlers aged 2-4, though anyone can be infected with Shigella.
What to doDrink plenty of fluids and get rest. Stay home from school or work to avoid spreading the bacteria to others. If you cannot drink enough fluids to prevent dehydration or have bloody diarrhea, call your doctor.
  • Wash hands with soap carefully and frequently, especially after going to the bathroom, after changing diapers, and before preparing foods or beverages.
  • Stay home from healthcare, food service, or childcare jobs while sick or until your health department says it's safe to return.
  • Keep children with diarrhea out of child care settings and school while they are ill.
  • Dispose of soiled diapers properly.
  • Disinfect diaper changing areas after using them.
  • Supervise handwashing of toddlers and small children after they use the toilet.
  • Do not prepare food for others while ill with diarrhea
  • Avoid swallowing water from ponds, lakes, or untreated pools.
  • Avoid having sex (vaginal, anal, or oral) for one week after you no longer have diarrhea.
  • When traveling in developing countries, drink only treated or boiled water, and eat only cooked hot foods or fruits you peel yourself.

Staphylococcus aureus
Staphylococcal (Staph) Food Poisoning

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SourcesPeople who carry the bacteria Staphylococcus aureus (Staph), which is commonly found on the skin, can contaminate food if they don't wash their hands before touching it. Foods that are not cooked after handling, such as sliced meats, puddings, pastries, and sandwiches, are especially risky if contaminated with Staph.
Incubation period30 minutes to 8 hours
SymptomsSudden start of nausea, vomiting, and stomach cramps. Most people also have diarrhea.
Duration of illness1 day
What to doDrink plenty of fluids. If you cannot drink enough fluids to prevent dehydration, call your doctor. Your doctor may give you medicine to decrease nausea and vomiting.
  • Use a food thermometer and cook foods to their safe minimum internal temperature.
  • Keep hot foods hot (140°F or hotter) and cold foods cold (40°F or colder).
  • Store cooked food in shallow containers and refrigerate within 2 hours (or 1 hour if it’s hotter than 90° F outside).
  • Wash your hands for 20 seconds with soap and water before, during, and after preparing food, and before eating.
  • Do not prepare food if you are ill with diarrhea or vomiting.
  • Wear gloves while preparing food if you have wounds or infections on your hands or wrists.

Vibrio Species Causing Vibriosis

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(Video) Virus vs Bacteria

SourcesMost people become infected by eating raw or undercooked shellfish, particularly oysters. Certain Vibrio species can also cause a skin infection when an open wound is exposed to salt water or brackish water. Brackish water is a mixture of fresh water and salt water. It is often found where rivers meet the sea.
Incubation period
  • Vibrio wound infection: 1–7 days
  • Gastrointestinal illness: 2–48 hours
  • In healthy people: Diarrhea, vomiting, abdominal pain
  • In high-risk people: Sudden chills, fever, shock, skin lesions
Duration of illness3 days, when spread through food. Duration of wound infections is variable.
What to doIf you have symptoms within a few days after eating raw or undercooked seafood, especially oysters, or develop a skin infection after being exposed to salt water or brackish water, contact your doctor. Don’t chance it! Some Vibrio species, such as Vibrio vulnificus, can cause particularly severe and life-threatening infections.
  • Don’t eat raw or undercooked oysters or other shellfish. Cook them before eating.
  • Always wash your hands with soap and water after handing raw shellfish.
  • Avoid contaminating cooked shellfish with raw shellfish and its juices.
  • Stay out of salt water or brackish water if you have a wound (including cuts and scrapes), or cover your wound with a waterproof bandage if there's a possibility it could come into contact with salt water or brackish water, raw seafood, or raw seafood juices.
  • Wash wounds and cuts thoroughly with soap and water if they have been exposed to seawater or raw seafood or its juices.

If you are in a group more likely to get a Vibrio infection, such as people with liver disease:

  • Wear clothes and shoes that can protect you from cuts and scrapes when in salt water or brackish water.
  • Wear protective gloves when handling raw seafood.

General Information

Foodborne Illnesses and Germs (CDC)

Bad Bug Book (FDA)


What is a common way that bacteria and viruses are spread your answer? ›

Nose, mouth, or eyes to hands to others: Germs can spread to the hands by sneezing, coughing, or rubbing the eyes and then can be transferred to other family members or friends. Simply washing your hands can help prevent such illnesses as the common cold or eye infections.

What's the difference between viruses and bacteria answer key? ›

On a biological level, the main difference is that bacteria are free-living cells that can live inside or outside a body, while viruses are a non-living collection of molecules that need a host to survive.

What do bacteria and viruses have in common? ›

Bacterial and viral infections have many things in common. Both types of infections are caused by microbes (bacteria and viruses) and are spread by things such as coughing and sneezing, contact with infected people, surfaces, food, water, pets, livestock, or insects such as fleas and ticks.

What are facts about bacteria and viruses? ›

Unlike organisms that are clearly alive, viruses don't need food, and they have no metabolism. They have only a handful of genes (often as few as just three or four), unlike bacteria, which have about a thousand genes, and higher forms of life — like humans — with tens of thousands of genes.

Do viral or bacterial infections spread? ›

Like bacterial infections, many viral infections are also contagious. They can be transmitted from person to person in many of the same ways, including: coming into close contact with a person who has a viral infection. contact with the body fluids of a person with a viral infection.

Where do viruses and bacteria come from? ›

To date, no clear explanation for the origin(s) of viruses exists. Viruses may have arisen from mobile genetic elements that gained the ability to move between cells. They may be descendants of previously free-living organisms that adapted a parasitic replication strategy.

What are the 3 main differences between bacteria and viruses? ›

Viruses are tinier: the largest of them are smaller than the smallest bacteria. All they have is a protein coat and a core of genetic material, either RNA or DNA. Unlike bacteria, viruses can't survive without a host. They can only reproduce by attaching themselves to cells.

What are 5 major differences between viruses and bacteria? ›

Difference Between Virus And Bacteria
They are living organismsThey can replicate only within the host cell
Mode of Reproduction
Reproduce asexually by binary fissionInsert their genome in the host genome and make multiple copies
Host Dependence
18 more rows

How are bacteria and viruses the same and different? ›

Key facts. Bacteria are single cells that can survive on their own, inside or outside the body. Viruses cause infections by entering and multiplying inside the host's healthy cells. It can be difficult to know what causes an infection, because viral and bacterial infections can cause similar symptoms.

How are bacteria and viruses related? ›

Bacteria cause bacterial infections. Viruses cause viral infections. Antibiotic medicines kill or keep many bacteria from growing but don't treat viruses. Antiviral medicines help the body clear out some viruses.

Why virus and bacteria are important in our life? ›

Microscopic creatures—including bacteria, fungi and viruses—can make you ill. But what you may not realize is that trillions of microbes are living in and on your body right now. Most don't harm you at all. In fact, they help you digest food, protect against infection and even maintain your reproductive health.

Where are viruses and bacteria found? ›

Germs live everywhere. You can find germs (microbes) in the air; on food, plants and animals; in the soil and water — and on just about every other surface, including your body. Most germs won't harm you. Your immune system protects you against infectious agents.

What are 3 facts about bacteria? ›

Bacteria are small single-celled organisms. Bacteria are found almost everywhere on Earth and are vital to the planet's ecosystems. Some species can live under extreme conditions of temperature and pressure. The human body is full of bacteria, and in fact is estimated to contain more bacterial cells than human cells.

Do viruses live bacteria? ›

Well, it turns out that most of the viruses in the world infect bacteria instead of people. Scientists call these viruses bacteriophages (which literally means “bacteria eaters”).

What kills bacteria inside the body? ›

Antibiotics are medicines that help stop infections caused by bacteria. They do this by killing the bacteria or by keeping them from copying themselves or reproducing. The word antibiotic means “against life.” Any drug that kills germs in your body is technically an antibiotic.

How long do bacterial infections last? ›

Symptoms in case of acute Bacterial Infections may get resolved spontaneously in a duration of approx. two weeks, without undergoing treatment. However, in chronic cases when the symptoms persist for a longer duration, such as for 10 or more days, there is a need for the consultation with a doctor.

How long can a bacterial viral infection last? ›

A viral infection usually lasts only a week or two. But when you're feeling rotten, this can seem like a long time! Here are some tips to help ease symptoms and get better faster: Rest.

What creates a virus? ›

Viruses might have come from broken pieces of genetic material inside early cells. These pieces were able to escape their original organism and infect another cell. In this way, they evolved into viruses. Modern-day retroviruses, like the Human Immunodeficiency Virus (HIV), work in much the same way.

How viruses are caused? ›

Common ways you can get viral infections include: From other people (through coughing, sneezing or close contact). From surfaces or objects that someone with a virus has touched (like countertops, doorknobs or phones). Through vaginal, oral or anal sex.

Do viruses grow yes or no? ›

Living things grow.

Viruses manipulate host cells into building new viruses which means each virion is created in its fully-formed state, and will neither increase in size nor in complexity throughout its existence. Viruses do not grow.

What causes bacteria infection? ›

What causes bacterial infections? A bacterial infection occurs when bacteria enter the body, increase in number, and cause a reaction in the body. Bacteria can enter the body through an opening in your skin, such as a cut or a surgical wound, or through your airway and cause infections like bacterial pneumonia.

What are 5 characteristics of viruses? ›

Characteristics of a Virus:
  • They reproduce at a spectacular rate, but only in live host cells.
  • They can be transformed.
  • They are acellular, i.e., they have no cytoplasm or cellular organelles.
  • They do not conduct any metabolism on their own and must replicate using the metabolic machinery of the host cell.

What are 4 types of bacteria? ›

Bacteria are classified into five groups according to their basic shapes: spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or corkscrew (spirochaetes).

What are the most common viruses and bacteria? ›

The bacteria and viruses that cause the most illnesses, hospitalizations, or deaths in the United States are described below and include:
  • Campylobacter.
  • Clostridium perfringens.
  • E. coli.
  • Listeria.
  • Norovirus.
  • Salmonella.
Mar 22, 2021

What are 3 similarities between bacteria and viruses? ›

Similarities Between Bacteria and Viruses

Both viruses and bacteria can cause diseases. Both can be spread through coughing, sneezing, or coming into contact with contaminated surfaces, animals, items, or people. Both can possibly be treated with vaccines.

Which is smaller bacteria or virus? ›

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.

Does bacteria have DNA? ›

Most bacteria have a haploid genome, a single chromosome consisting of a circular, double stranded DNA molecule.

Do virus and bacteria fight each other? ›

But bacteria and viruses have also been fighting each other for a very long time, and studying the way they fight has taught us a lot about how organisms change over time and has also led to the discovery of an extremely exciting research tool. This battle between bacteria and viruses is about the ability to reproduce.

How can the virus control the bacteria? ›

The phages infiltrate bacterial cells, where they commandeer the host machinery to make thousands of new phages; then they escape through the bacterial cell wall--killing the host--and spread to infect their next victims. Some phages break out using an enzyme that digests the cell wall.

Why are bacteria so important? ›

Bacteria help many animals to digest food, they help trees grow, and they are important in the recycling of nutrients in the environment. They are also used in biotechnology applications to produce everything from food to energy to clean water. Bacteria can be very helpful to humans and other organisms.

How are viruses important to humans? ›

Viruses also keep us alive. They form part of the body's microbiome and safeguard our health. They can be harnessed to treat illness, deliver vaccines, and diagnose infections. They're wielded as research tools to illuminate biology and disease and develop new drugs.

What is the role of bacteria in human body? ›

The bacteria in our bodies help degrade the food we eat, help make nutrients available to us and neutralize toxins, to name a few examples[7]; [8]. Also, they play an essential role in the defense against infections by protecting colonized surfaces from invading pathogens[8]; [9].

How many bacteria and viruses are in the human body? ›

Viruses are the most numerous organisms on earth. While we are thought to have roughly the same number of bacterial cells as human cells in our body (around 37 trillion), we probably have at least 10 times as many virus particles again.

Can bacteria cause disease? ›

Infectious diseases can be caused by: Bacteria. These one-cell organisms are responsible for illnesses such as strep throat, urinary tract infections and tuberculosis.

Which bacteria is a virus? ›

Bacteria can be infected by tiny viruses called bacteriophages (phages). Bacteriophages are so small they do not even have a single cell, but are instead just a piece of DNA surrounded by a protein coat.

What does bacteria eat? ›

Bacteria are like all living organisms, they need to eat for energy and growth. But what do bacteria eat? Well, many bacteria eat starches and sugars which can be found on more or less all organic matter.

What are bacteria in short answer? ›

Bacteria are tiny, single-celled living organisms. There are millions of different types of bacteria. Many can be found in and on your body and are beneficial to you. These bacteria make up your microbiome, which keeps your body healthy.

What does bacteria need to survive? ›

Bacteria can live in hotter and colder temperatures than humans, but they do best in a warm, moist, protein-rich environment that is pH neutral or slightly acidic. There are exceptions, however. Some bacteria thrive in extreme heat or cold, while others can survive under highly acidic or extremely salty conditions.

What is bacteria made of? ›

It is a gel-like matrix composed of water, enzymes, nutrients, wastes, and gases and contains cell structures such as ribosomes, a chromosome, and plasmids. The cell envelope encases the cytoplasm and all its components. Unlike the eukaryotic (true) cells, bacteria do not have a membrane enclosed nucleus.

How many bacteria are in the human body? ›

What is the microbiome? In any human body there are around 30 trillion human cells, but our microbiome is an estimated 39 trillion microbial cells including bacteria, viruses and fungi that live on and in us.

Do viruses infect all life? ›

Viruses infect all cellular life. Their evolution is inextricably bound to their target cells. Whether lyzing cells as part of a lytic cycle or inserting their DNA into the host genome in the lysogenic cycle, viruses place selective pressure on cells to evolve counter measures to evade infection.

Do bacteria have immune system? ›

Like humans, bacteria have various immune systems to defend against pathogens such as viruses. These immune systems usually degrade the DNA of the pathogens to make it harmless.

Do viruses have DNA? ›

Unlike cells (e.g. bacteria, plant and animal cells), viruses contain either DNA or RNA, never both; the viral nucleic acid is either single or double stranded. Viruses with a DNA core are capable of surviving in the nucleus of the cell they infect, using the host's biochemical machinery to replicate their DNA.

What is the most common way through which bacteria spreads? ›

Germs can spread in a number of ways, but the most common are by direct and indirect contact and through the air.

What is the most common methods for spreading viruses in system? ›

Typically, computer viruses spread through malicious online downloads, infected email attachments, or by plugging in infected hardware like an external flash drive (USB stick). Computer viruses can spread through almost any method of file sharing, as long as the virus can avoid detection by antivirus programs.

What are the most common carrier of viruses and bacteria? ›

Contaminated food, especially undercooked ground beef, unpasteurized (raw) milk and juice, soft cheeses made from raw milk, and raw fruits and vegetables (such as lettuce, other leafy greens, and sprouts). Contaminated water, including drinking untreated water and swimming in contaminated water.

What is the most common way infectious diseases are spread? ›

Person to person spread. This is the most common way that we get an infectious disease. Germs can spread from person to person through: the air as droplets or aerosol particles.

What human disease is caused by bacteria? ›

Common bacterial diseases include UTIs, food poisoning, STIs and some skin, sinus and ear infections. They're often treated with antibiotics.

How long does bacteria live? ›

Bacteria divide somewhere between once every 12 minutes and once every 24 hours. So the average lifespan of a bacterium is around 12 hours or so. Read more: Are any bacteria visible to the naked eye?

What happens when bacteria makes someone sick? ›

Sometimes bacteria multiply so rapidly they crowd out host tissues and disrupt normal function. Sometimes they kill cells and tissues outright. Sometimes they make toxins that can paralyze, destroy cells' metabolic machinery, or precipitate a massive immune reaction that is itself toxic.

How do I remove a virus infection? ›

How to remove malware such as a virus, spyware, or rogue security software
  1. Install the latest updates from Microsoft Update. ...
  2. Use the free Microsoft Safety Scanner. ...
  3. Use the Windows Malicious Software Removal Tool. ...
  4. Manually remove the rogue security software. ...
  5. Run Microsoft Defender Offline.

How can we protect ourselves from viruses? ›

In those situations, use as many prevention strategies as you can, such as practicing hand hygiene, consistently and correctly wearing a high-quality mask, improving ventilation, and keeping your distance, when possible, from the person who is sick or who tested positive.

What are the 3 types of viruses? ›

Based on their host, viruses can be classified into three types, namely, animal viruses, plant viruses, and bacteriophages.

What temperature kills viruses and bacteria? ›

According to World Health Organization, temperatures of at least 140 degrees Fahrenheit (60 degrees Celsius) are enough to kill most viruses. Boiling water can kill off the bacteria on food and running your dishwasher is enough to sterilize your dishes from germs.

What does bacteria need to grow? ›

Bacteria can live in hotter and colder temperatures than humans, but they do best in a warm, moist, protein-rich environment that is pH neutral or slightly acidic.

How do you know if your body is fighting an infection? ›

Fever (this is sometimes the only sign of an infection). Chills and sweats. Change in cough or a new cough. Sore throat or new mouth sore.

How do you prevent bacterial infections? ›

Warding off germs and infection
  1. Avoid close contact with people who are sick.
  2. Cover coughs and sneezes.
  3. Avoid touching your face.
  4. Stay home if you're sick.
  5. Clean and disinfect surfaces that are touched often.
  6. Avoid contaminated food and water.

What causes viral infection? ›

What causes viral infections? Many different types of viruses can cause infections, though only a few infect humans. They can get into your body through your nose, mouth, eyes, anus or genitals, or through a break in your skin. Once there, they get inside of your cells and use them to make more copies of themselves.


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