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The Difference Between a Bacterial and Viral Infection

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The Difference Between Bacteria and Viruses


Bacteria are mostly unicellular prokaryotic organisms. Bacteria are cells which have their metabolism and reproduce by means of cell division. Bacteria have a number of shapes, including spheres which are called cocci (staphylococcus, streptococcus, pneumococcus, meningococcus, etc.) and rods (colon bacillus, Bordetella pertussis, dysentery bacillus, etc.).

A lot of bacteria living on our skin, mucous membranes and in the digestive system areharmless, but they may become pathogenic due to a weakened immune system or immune system disorders.

Unlike bacteria, viruses are parasites which cannot replicate outside of a cell. They enter a cell forcing it to generate their copies. When a cell is infected, special mechanisms of protection against viruses are activated. Infected cells begin to release interferons causing nearby cells to heighten their antiviral defenses and triggering the protective defenses of the immune system that help fight viruses.

Some viruses can stay in the body for a lifetime, lying latent and reactivating under certain conditions. These viruses include herpes viruses, papillomaviridae and HIV. While in the latent phase, the virus can be killed neither by the immune system nor by medications.

Acute Respiratory Viral Infections (ARVI)

ARVI are airborne viral infections of the upper airways. Respiratory viral infections are the most common infectious diseases.

All ARVI have a short incubation period varying from 1 to 5 days. The incubation period is the period taken by a multiplying virus to reach a threshold necessary to produce the first symptoms.

The incubation period is followed by a prodromal period (prodrome). This is a period when a virus has spread over the body but the immune system has not responded to it yet. This is when the first symptoms occur, such as flaccidity, capriciousness, rhinitis and pharyngitis. During the prodromal period, antiviral drugs are the most effective.

The next phase is the onset of the disease. As a rule, ARVI symptoms start quickly. These include fever (38-39 °С), headache, chills, running nose, cough, and a sore throat. Try to remember when you were infected, meaning when the exposure to an infected patient occurred. If it has been more than five days since the exposure, it is probably a viral infection.

Generally, viral infections require symptomatic treatment that includes antipyretics, expectorants, etc. Antibiotics do not kill viruses.

The most common viral infections include flu, ARVI, herpetic infections, viral hepatitis, HIV, measles, German measles, parotitis, chicken pox, tick-borne encephalitis, hemorrhagic fever, poliomyelitis, etc.

Blood Picture in Viral Infections

White blood cell counts are within or fall slightly below the normal range. Rarely, they may be slightly above the normal range. Changes in the white blood count occur due to an increase in lymphocytes and/or monocytes and, consequently, a decrease in neutrophils. ESR values may rise slightly, however the erythrocyte sedimentation rate may be very high in severe ARVI.

Bacterial Infections

Bacterial infections may occur on their own or together with a viral infection because viruses suppress the immune system.

A major difference between bacterial and viral infections is the fact that bacterial infections have a longer incubation period that varies from 2 to 14 days. As for bacterial infections, take into consideration not only when exposure to an infected patient may have occurred, but also whether or not you have experienced stress or have been exposed to cold temperatures lately. Some bacterial infections may stay in the body for years without causing any symptoms and reactivate in response to a weakened immune system.

Bacterial infections often have no prodromal period. For instance, a bacterial infection may start as a complication of ARVI. While viral infections often develop due to the deterioration of general health, bacterial infections normally have a local manifestation (angina, otitis, sinusitis). The patient’s body temperature does not rise above 38 degrees.

Bacterial infections are treated with antibiotics. Early treatment may help prevent complications. The misuse of antibiotics is a contributing factor to the creation of bacteria resistant to antibiotics. Antibiotics should always be taken as prescribed by your doctor.

Bacterial infections most often cause genyantritis, otitis, pneumonia and meningitis (although pneumonia and meningitis may be caused by viruses as well). The most common bacterial infections include whooping cough, diphtheria, tetanus, tuberculosis, most enteric infections, syphilis, gonorrhea, etc.

Blood Picture in Bacterial Infections

White blood cell counts are slightly above the normal range due to an increase in neutrophils. The so-called "left shift" occurs, that is increased proportions of band neutrophils and, possibly, younger neutrophils, such as metamyelocytes (juvenile cells) and myelocytes. This may lower the relative concentration (percentage) of lymphocytes. The ESR (erythrocyte sedimentation rate) is usually quite high.

Automatic interpretation of the Complete Blood Count (CBC) with differential


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