Infection occurs due to the invasion of organisms or disease-causing agents such as bacteria, virus, fungi, or parasites. Infectious disease is the illness that occurs due to infection. Infectious disease is also known as transmissible or communicable disease.
Infection is not same as the infectious disease as all infections don't cause illness in the host. Some organisms invade the host but remain asymptomatic. Some infections are life-threatening (e.g. pneumonia and meningitis) whereas some infections cure and may cause complications in later stages (chicken pox leading to shingles).
Infectious diseases, if they are chronic and persistent, are resulting in millions of deaths globally every year.
Signs and symptoms of the infectious diseases depend on the causative organism and differ for each infection.
Bacteria cause infectious diseases such as tuberculosis, pneumonia, and meningitis. Viruses cause illnesses ranging from common cold to dreadful HIV. Examples of fungal infections are athlete’s foot, candidiasis, etc. Parasitic infections can occur due to protozoa, helminths, or ectoparasites. Trichomoniasis and giardiasis are examples of the parasitic infections.
After the invasion of the organism, the protective mechanisms of the body fight against the organism. The disease occurs when these mechanisms are compromised, and the damage to the body by the organism begins. The organisms damage tissues of the host by releasing some chemical toxins. The type and effect produced by the toxins in the body vary depending on the organism.
Infectious diseases can transmit through direct or indirect contact. Direct contact can be from person to person, animal to person, and mother to fetus. Indirect contact can be through carriers or vectors and food contamination.
The routes of transmission can be through droplet, sexual, oral, fecal-oral, iatrogenic, vertical, or vector-borne.
Anyone of us can get infectious diseases. But the chances increase if your immune system is weakened or compromised. This may be due to conditions such as HIV or cancer and use of medications such as steroids that suppress the immune system. Elderly people are more likely to develop infections as they suffer from comorbidities.
Your doctor gives a provisional diagnosis based on your symptoms. Body fluids are analyzed to reveal presence and type of organism present. Samples for laboratory tests include blood, urine, stool, throat swab, and spinal fluid. Spinal fluid is obtained through lumbar puncture. Your doctor would recommend one or more of these tests based on your symptoms. A microbial culture test is performed with the sample obtained to detect the organism.
Imaging tests such as X-rays help to rule out conditions that have similar symptoms. In few cases, your doctor may also recommend a biopsy to confirm the diagnosis.
Your doctor chooses an appropriate treatment based on the causative organism.
Antibiotics are prescribed if the infection is caused by bacteria. Few exceptions such as tuberculosis, anti-tubercular drugs are given rather than antibiotics. These medications can be bacteriostatic or bactericidal. Your doctor may prescribe oral, topical, or intravenous antibiotics based on the type and severity of the infection.
Antivirals are given to treat some, but not all viral infections. Antivirals are prescribed to treat conditions such as HIV, herpes, influenza, and hepatitis. Antifungals are given for fungal infections and anti-parasitics are given for parasitic infections.
All infections don’t require treatment, as some of the conditions are self-limiting. So, drink plenty of fluids and have adequate rest when you are ill. Follow some measures to prevent new or recurrent infections.