Not all germs are harmful. In fact, some even help us to stay healthy. They can be found on and within our bodies at all times — in addition to the air, soil, and water. Germs spread easily from person to person or by coming in contact with contaminated objects or surfaces. But even if only a small proportion of germs are harmful, these microorganisms are still a major cause of infections and related illnesses.
Understanding how germs spread, taking certain precautions, and practicing proper hygiene are the keys to maintaining good health and preventing illnesses. Our guide covers common forms of viral and bacterial infections caused by the transmission of germs, as well as some simple, yet effective measures to prevent the spread of germs and minimize your risk of contracting an infection.
Germs don’t move by themselves, so transmission from person to person or place to place depends on your habits and the environment.¹ For you to contract an infection — for germs to enter your body, multiply, and cause a reaction — two conditions must be met:
Germs are typically spread through direct contact (physical touch), spraying or splashing (via uncovered coughs or sneezes), or the inhalation of aerosolized particles. In medical settings, infections also occur when bloodborne pathogens are accidentally transmitted via the prick or puncture of a contaminated needle.
Viruses are tiny packets of genetic material, either DNA or RNA, surrounded by a protein shell (sometimes with fatty materials called lipids).² Unlike bacteria, viruses cannot survive outside of a living cell nor reproduce on their own. They only become active once they have infected a host cell. Then, using the host cell’s metabolic resources, the virus begins making copies of itself. This is the beginning of infection — when viruses, bacteria, or other microbes enter your body and start to reproduce.
Virus particles enter our bodies all the time, but only a small percentage of infected people develop a disease; symptoms of an emerging disease appear only when cells are damaged. When your immune system is trying to eliminate infection and stop cell destruction, symptoms like fever, malaise, headaches, and rashes often occur.
Viruses can potentially stay infectious for several hours to days, depending on the surface. Plastic, stainless steel, and other nonporous hard surfaces are more likely to keep viruses alive for longer periods of time.¹³ ¹⁴ The length of time a virus lives on a dry surface also varies by virus type; the following list details some examples:¹⁴ ¹⁵
There are millions of cases of the common cold each year; adults typically have 2-3 colds annually, whereas children tend to have more.³ The most common causes of colds are rhinoviruses, which can also trigger asthma attacks and contribute to sinus and ear infections. Other viruses that can cause colds include:³
After the first signs of a cold appear — typically a sore throat and runny nose, followed by coughing and sneezing — most people make a full recovery within 7-10 days. Other common symptoms you may experience are headaches and body aches. If you experience a fever or chills, severe or unusual symptoms, or if your cold lasts over ten days, the CDC recommends contacting your doctor.³
If you have a child under three months old who develops a fever or becomes lethargic, contact their pediatrician. Additionally, as a precaution, those who are at risk for serious flu complications (children younger than five, older adults over 65, pregnant individuals, and people with asthma, diabetes, or heart disease) should contact a health professional if they experience fever, chills, or body aches. When people with weakened immune systems, asthma, or respiratory conditions catch colds, they’re at risk of developing more serious illnesses such as bronchitis or pneumonia.³
The best ways to reduce your risk of getting a cold (as well as most other viruses) are:³ ¹⁴
The flu is a contagious respiratory illness caused by influenza viruses that infect an average of about 8% of the U.S. population every year.⁴ Flu viruses primarily affect the nose, throat, and occasionally the lungs. They are typically spread through tiny respiratory droplets emitted when an infected person coughs, sneezes, or talks. While not as likely, you can also become infected by touching your mouth, nose, face, or eyes after touching a surface or object with a flu virus on it.
Often appearing suddenly, common flu symptoms include:⁴ ¹⁶
Most commonly seen in children, vomiting and diarrhea are also possible symptoms. And not everyone who catches the flu will develop a fever.
People with the flu are most contagious in the first 3-4 days after infection, but it’s possible to infect others 5-7 days before the first sign of symptoms. For some people, especially young children and those with weakened immune systems, it’s possible to spread influenza to others for even longer. According to the CDC, the best way to prevent common influenza infections is by getting your yearly flu shot.⁴
Caused by a novel coronavirus (SARS-CoV-2), the first case of COVID-19 was reported on December 1, 2019. COVID-19 is widely believed to have originated in an animal and then mutated to cause illness in humans.⁵ Symptoms typically appear 2-14 days after exposure, and an infected person may be contagious up to 48 hours before experiencing any symptoms. Depending on the strength of their immune system and the severity of their illness, they can remain contagious for around ten days.⁵ ¹⁷
Common symptoms of COVID-19 include:⁵ ¹⁷
Some individuals infected with COVID-19 experience mild or no symptoms. However, COVID-19 can also be fatal or lead to other serious complications:⁵
Since many of the signs and symptoms of COVID-19 are also found in other illnesses, doctors almost always diagnose COVID-19 using a test.
The severity of the infection determines the proper treatment for COVID-19. For milder cases, bed rest and fever-reducing medications are often enough. For more severe cases, though, hospitalization is often required, where interventions can include:⁵ ¹⁷
The coronavirus that causes COVID-19, like other viruses, can also mutate. This results in more and more new variants, which often spread quickly from person to person. More infections mean more opportunities for the virus to mutate, generating further variants. General COVID-19 safety and prevention methods are:⁵ ¹⁷
RSV is a common respiratory virus that, in most people, causes mild, cold-like symptoms.⁶ RSV infections can be more serious, especially in infants and older adults, but most people fully recover in under two weeks. Symptoms associated with RSV usually appear in stages, 4-6 days after infection; the most common symptoms are:⁶ ¹⁸
Infants with RSV may show signs of irritability, decreased activity, and difficulty breathing, but healthy infants (and adults) rarely require hospitalization.¹⁸ In the U.S., RSV is the most common cause of bronchiolitis and pneumonia in children under one-year-old; almost all children will have contracted RSV by their second birthday.⁶
Older adults and infants (under six months old) might require hospitalization if they have trouble breathing or become dehydrated. Hospitalization will typically only last a few days. But, in severe cases, additional oxygen, IV fluids, or intubation can be necessary.⁶
Vaccines and antivirals for the treatment of RSV are not widely available yet but should be soon. Non-prescription cold medicines are an option, but some contain ingredients that are unsafe for children, so be sure to consult a healthcare professional before administering them to your child. To relieve symptoms, you can also try over-the-counter fever reducers and pain relievers, such as acetaminophen or ibuprofen. It’s also important for those infected with RSV to stay well hydrated.⁶ ¹⁸
Although commonly referred to as the stomach flu (or a stomach bug), viral gastroenteritis differs significantly from influenza.⁷ Influenza primarily affects your respiratory system (nose, throat, and lungs), while viral gastroenteritis attacks your intestines. The most common cause of stomach flu is exposure to an infected person or consuming contaminated food or water.
Symptoms of viral gastroenteritis often appear 1-3 days after infection and can range from mild to severe, depending on the source of infection. Symptoms will typically last just 24-48 hours but, in some cases, can last for up to two weeks. Common symptoms include:⁷
If you’re healthy otherwise, you will more than likely recover quickly and without complications. However, a severe stomach bug can be deadly for infants, older adults, and people with compromised immune systems. Given that there's currently no specific treatment for stomach flu, the best medicine remains proper prevention, such as avoiding food or water that might be contaminated and washing your hands thoroughly and often.⁷
Because viral diarrhea and diarrhea caused by bacteria consist of a similar experience, it’s not uncommon to mistake the stomach flu for a bacterial infection, such as Clostridioides difficile (C. diff.), Escherichia coli (E. coli.), Salmonella, or a parasitic infection, such as Giardia.
The herpes simplex virus (HSV) is highly contagious and infects millions of people worldwide. Primarily spread through skin-to-skin contact, there are two types of HSV: HSV-1 and HSV-2. HSV-1 is responsible for oral herpes, while HSV-2 causes genital herpes.²⁴ Infections are usually asymptomatic or come with mild symptoms but, in some cases, painful blisters or ulcers can occur and reoccur over time.¹¹ If symptoms do appear, they’re usually at their worst during the initial appearance, with recurrences being much milder.²⁴
HSV lives inside nerve cells and alternates between being inactive (no symptoms) and active (symptoms). Certain triggers may activate the virus, including:¹¹
Medications, such as paracetamol (acetaminophen), naproxen, or ibuprofen, can help relieve pain associated with sores; while topical anesthetics, such as benzocaine and lidocaine, can also be applied to numb the affected area. For those who have frequent or severe outbreaks or want to reduce the risk of transmitting the virus to others, further treatment is recommended. Prescription medications that can help alleviate symptoms are available, but these medications are not a cure and must be taken continuously to prevent outbreaks.¹¹ ²⁴
Pregnant individuals who experience symptoms of genital herpes should inform their OB-GYN, as it is important to avoid getting an HSV-2 infection toward the end of pregnancy (when the risk of neonatal herpes is highest). Anyone who thinks they might have genital herpes should also consider getting tested for HIV.¹¹
To prevent the spread of oral herpes, symptomatic individuals should avoid oral contact with others or share objects that have come into contact with their saliva. Those suffering an outbreak of genital herpes should not have sex during an outbreak. HSV-1 and HSV-2 are most contagious during outbreaks but can also be transmitted when no symptoms are present. Using condoms consistently during sex can lower the risk of getting genital herpes, as well as other STIs. However, there’s still a chance of getting infected through contact with uncovered areas of the genitals or anus.¹¹ ²⁴
Bacteria are single-celled microorganisms that can live in a range of different environments, including on and in the human body. There are many kinds of bacteria, but only some cause infections. While most bacteria are not harmful (they can play a major role in digestion), some can cause harmful diseases depending on how you’re exposed and what part of your body is affected.⁸ ¹⁹
Bacteria, like E. coli and Salmonella, can live on hard surfaces for up to four hours, and C. diff can persist on hard, nonporous surfaces for up to five months.⁸ Some researchers have also found Staphylococcus aureus (including MRSA) to last for months on dry surfaces.¹⁵
Bacterial infections most often occur when bacteria enter your body through your mouth, nose, eyes, or a cut in your skin.⁸ The most common symptoms associated with bacterial infections are fever, chills, fatigue, and headache, and the most common types of bacterial infections include:⁸ ²⁰
While some bacterial infections are contagious — including pertussis, tuberculosis, strep throat, meningococcal disease, bacterial STIs, and Methicillin-resistant Staphylococcus aureus (MRSA) — infections from food, mosquitos, or ticks are usually not. There are several ways in which bacterial infections commonly spread:⁸
Contaminated dust or droplets (water or mucus) travel through the air and into the body of a susceptible host. Legionnaires’ disease, pertussis (whooping cough), tuberculosis, meningococcal disease, and strep throat are all transmitted this way.
Through direct contact with infected skin or mucous membranes, or via indirect contact with contaminated surfaces, it’s possible to contract skin infections as well as some sexually transmitted infections (STIs), such as gonorrhea and chlamydia.
Vector-borne infections are those contracted from bugs, such as mosquitos, ticks, or fleas. Common vector-borne infections include Rocky Mountain spotted fever and Lyme disease.²¹
The “vehicle” of transmission for some forms of bacteria — including E. coli, Campylobacter, and Salmonella — is often contaminated food or water, and gastrointestinal infections are frequently the result.
While some bacterial infections will clear up on their own, others require treatment. If you are experiencing symptoms of a bacterial infection, contact your healthcare provider. If treatment is necessary, they will likely prescribe antibiotics. The type of antibiotic prescribed (oral, eye drops, IV, ointments, or creams) will depend on the location and severity of the infection. A course of antibiotics may last 1-2 weeks, and although you may begin to feel better sooner, it's highly important to take all medications as prescribed.⁸ ²⁰
If symptoms don't improve, follow up with your healthcare provider. Signs of a more serious infection potentially requiring immediate medical attention include:⁸
MRSA is a type of antibiotic-resistant staph bacteria commonly found in hospitals and other healthcare settings, such as nursing homes and dialysis centers.⁹ ²² Staph bacteria, the cause of MRSA, are found on the skin or in the nose of about one-third of the population but, in healthy people, usually only cause minor skin problems. MRSA infections usually begin as red bumps that are warm to the touch and filled with pus. You should contact your healthcare provider if you develop a fever or notice a wound becoming infected.⁹ ²²
For many years, doctors have prescribed antibiotics for colds, flu, and other viral infections that do not respond to these treatments. As a result, MRSA is resistant to many common antibiotics, which makes it difficult to treat. Bacteria evolve quickly, so germs that survive treatment with one antibiotic soon learn to resist other antibiotics.⁹
In a hospital setting, patients who are infected or colonized with MRSA are often placed in isolation, while visitors and staff are encouraged to follow strict hand hygiene procedures and wear protective garments. Patient rooms and potentially contaminated equipment are also disinfected and cleaned regularly.⁹ ²³
Antibiotic or antimicrobial resistance (AMR) occurs when microorganisms such as bacteria, viruses, fungi, and parasites develop resistance to antimicrobial drugs that were previously effective.¹⁰ This means that infections caused by these microorganisms become more difficult or impossible to treat, leading to prolonged illness, longer hospital stays, higher healthcare costs, and increased mortality rates.
Caused by the overuse and misuse of antimicrobial drugs, AMR has become a major global health concern. In 2019, AMR was associated with nearly five million deaths and killed at least 1.27 million people worldwide. In the U.S. alone, there are over 2.8 million antimicrobial-resistant infections yearly. AMR affects people of all ages and industries, including healthcare, veterinary, and agriculture. And bacteria or fungi resistant to even one antibiotic or antifungal can lead to serious issues:¹⁰
Essentially, the diminished effectiveness of antibiotics and antifungals could mean the loss of our ability to treat infections and control related public health threats.
Infections can have serious and sometimes fatal consequences. Therefore, taking necessary precautions to prevent both viral and bacterial infections is important. Here are some useful measures you can use to prevent infections:¹²
Wash your hands thoroughly, cover your mouth and nose when coughing or sneezing, wash and bandage all cuts, avoid sharing dishes and utensils, and avoid direct contact with items used by others.
To prevent food-borne infections, rinse all meat, poultry, fish, fruits, and vegetables before cooking or serving them, wash your hands before and after handling raw meat, separate raw and cooked foods, thoroughly cook food items, and only defrost foods using the refrigerator or microwave.
Children should receive recommended vaccinations, adults should ensure their vaccinations are up to date, and travelers should check with their healthcare provider about additional immunizations. Keeping your pet's vaccinations up to date is also important.
Get all necessary immunizations before leaving for your trip, especially if you’re traveling to an area where insect-borne diseases are common. It's also a good idea to avoid unnecessary shots, immunizations, or tattoos while abroad. If you’re not certain about the cleanliness of the water, drink only bottled beverages; this also applies to consuming ice, brushing your teeth, and washing fruits and vegetables.
The only way to completely prevent STIs is to abstain from all sexual contact. But for those who do plan to have sex, it’s recommended to engage in sexual contact with only one partner, ideally one who is only having sex with you. Using condoms and getting regular testing for HIV and STIs is also encouraged.
Using an EPA-approved insect repellent, limiting outdoor activity during peak mosquito hours, and draining any nearby standing water are all good ways to prevent the spread of germs and viruses carried by mosquitoes, ticks, and other bugs. Also, if you’ve been outdoors, thoroughly check yourself and your pets for ticks.
Rodents can harbor numerous pathogens, so controlling the population of mice and rats in and around your home can help prevent the spread of certain pathogens. To avoid getting sick from diseases transmitted by other animals, keep food and garbage in covered, rodent-proof containers, seal up any holes or cracks that might let animals into your home, clear away any brush or junk, and stay clear of wild animals.
Using hot water and household cleaners with soap or detergent in your kitchen and bathroom will remove germs on hard surfaces and reduce your risk of infection. After cleaning with soap or detergent, you can consider sanitizing with weakened bleach solutions or sanitizing sprays. According to the CDC, though, for everyday cleaning, you shouldn’t need to sanitize these areas unless someone in your household is sick.²⁵ If you’re concerned about cross-contamination when cooking with raw meat, eggs, or other potential contaminants, the USDA recommends cleaning first, then sanitizing your kitchen.²⁶
For soft items like clothing, towels, and bed linens, use detergent and wash in water at the temperature recommended by the item’s manufacturer. Try to make sure items are completely dried. The CDC notes that it is safe to wash laundry from an individual who is sick with other non-infected people’s items.²⁵
Pet bowls should be cleaned after every use of wet food and after every day of dry food or water. Your furry friend’s beds, blankets, and habitats or enclosures should be cleaned weekly, and their toys should be cleaned monthly. These items should generally only need cleaning with soap and water (or detergent if it’s a soft item). Disinfecting is normally reserved for items that come in contact with a pet’s urine or feces (like a litter box) or if your pet is sick. If you have reptiles, amphibians, or rodents, their items should be disinfected every month, as they’re more likely to carry germs that can make humans sick.²⁷
Cloth toys can be added to the laundry, while you should clean hard surface toys with soap and water, then sanitize them. You can sanitize nonporous toys and infant feeding items by boiling them, steaming them, or using a weak bleach solution. Some dishwashers have a sanitizing cycle that can be used for this purpose, too. These items should be air-dried on a clean dish towel or paper towel before storage or use.²⁵ The CDC also offers a guide dedicated to frequently asked questions about cleaning, sanitizing, and storing infant feeding items.
Understanding how germs spread and practicing proper hygiene is crucial to minimizing our risk of infection. Typically spread through direct contact, spraying or splashing, or inhalation of aerosolized particles, harmful germs first need a suitable place to live outside the body; then, once they’ve found their way into the body of a susceptible host, infection is often the result.
Although they can share similar symptoms, bacterial and viral infections are caused by different microorganisms. Bacteria are single-celled and can live outside the human body, while viruses are smaller and need a living host to reproduce. Bacterial infections, such as strep throat, UTIs, and pneumonia, can be treated with antibiotics, while the flu, common cold, and HIV are commonly treated with a range of antiviral medications.
You can prevent infections by following proper personal hygiene practices, ensuring food safety, getting vaccinated, and taking travel precautions. Practicing safe sex, preventing bug and tick bites, and controlling pests are also essential measures to minimize your risk of infection. These basic safety principles apply to most healthy people and can significantly reduce your chances of getting ill. It’s also important to remember that some people are more vulnerable to infections than others, and following these principles can also help protect them.
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