Herpes simplex is a type of virus that belongs to the family Herpesviridae and is characterized by its double stranded DNA structure. This virus is further classified into two types, HSV-1 and HSV-2. HSV-1 is responsible for the majority of orolabial infections, commonly known as cold sores, and is typically acquired through direct physical contact such as kissing. On the other hand, HSV-2 is primarily responsible for genital herpes, a sexually transmitted infection.

The fact that herpes simplex is a double stranded DNA virus is important because it helps in understanding its replication process and potential treatment options. Knowing the type of virus can also aid in developing effective prevention strategies and vaccines.

The 4-year-old boy presented with fever and left-sided focal fits, which could be indicative of either meningitis or encephalitis. Both conditions require prompt diagnosis and treatment to prevent potential complications. In this case, the investigation of choice to arrive at a diagnosis is CSF analysis.

CSF analysis involves obtaining a sample of cerebrospinal fluid through a lumbar puncture and analyzing it for various parameters such as cell count, protein levels, glucose levels, and culture for bacteria or viruses. This test can help differentiate between pyogenic meningitis (bacterial infection) and other forms of meningitis or encephalitis.

While other investigations such as blood cultures, ESR, and urine cultures may also be helpful in ruling out other potential causes of fever, CSF analysis is the most specific test for diagnosing meningitis or encephalitis. Additionally, advanced neuroimaging and EEG may be necessary to further evaluate the extent of brain involvement and to guide treatment.

In conclusion, given the clinical presentation of the child, CSF analysis is the most appropriate investigation to help arrive at a definitive diagnosis and initiate appropriate treatment.

Epididymo-orchitis is likely caused by enteric organisms, such as E. coli, in individuals with a low risk of sexually-transmitted infections (STIs), such as married men in their 50s with a single long-term partner. Therefore, the most appropriate next step would be to arrange a mid-stream urine sample for microscopy and culture to guide antibiotic treatment. This patient has subacute onset of testicular pain and swelling with associated dysuria, and his pain is relieved when elevating the testis (positive Prehn’s sign), making a diagnosis of testicular torsion less likely. A urethral swab sample for microscopy and culture is no longer the initial investigation of choice, and a urine sample for nucleic acid amplification tests (NAAT) is not appropriate in this case. Urgent referral for a same-day testicular ultrasound scan is also not necessary as testicular torsion is rare in patients over 35 years of age and does not present with dysuria.

Epididymo-orchitis is a condition where the epididymis and/or testes become infected, leading to pain and swelling. It is commonly caused by infections spreading from the genital tract or bladder, with Chlamydia trachomatis and Neisseria gonorrhoeae being the usual culprits in sexually active younger adults, while E. coli is more commonly seen in older adults with a low-risk sexual history. Symptoms include unilateral testicular pain and swelling, with urethral discharge sometimes present. Testicular torsion, which can cause ischaemia of the testicle, is an important differential diagnosis and needs to be excluded urgently, especially in younger patients with severe pain and an acute onset.

Investigations are guided by the patient’s age, with sexually transmitted infections being assessed in younger adults and a mid-stream urine (MSU) being sent for microscopy and culture in older adults with a low-risk sexual history. Management guidelines from the British Association for Sexual Health and HIV (BASHH) recommend ceftriaxone 500 mg intramuscularly as a single dose, plus doxycycline 100 mg orally twice daily for 10-14 days if the organism causing the infection is unknown. Further investigations are recommended after treatment to rule out any underlying structural abnormalities.

HIV Seroconversion Illness: Diagnosis and Differential Diagnosis

HIV-related seroconversion illness is a non-specific illness that occurs between one to six weeks following infection. It often mimics infectious mononucleosis but may have additional signs such as oral candidiasis or CNS symptoms. The best way to diagnose acute infection is by the presence of p24 antigen or HIV RNA by PCR. Malaria is less likely in this case than HIV, and stool culture would be useful in the diagnosis of gastroenteritis but is unlikely to be the cause of symptoms in this case. A CT chest, abdomen, and pelvis is non-specific and would not yield the diagnosis. A genital swab would be of benefit if there were suspicions of other sexually transmitted infections, but the symptoms and timing of onset in this case clearly point towards HIV seroconversion. It is important to consider HIV testing and prevention in patients with risk factors for infection.

The life cycle of Plasmodium species involves both a Dipteran insect host and a vertebrate host. The cycle begins when sporozoites are injected into the vertebrate host’s blood by the insect vector. These sporozoites then infect the host’s liver, where they give rise to merozoites and, in some species, hypnozoites. The merozoites move into the blood and infect red blood cells.

Within the red blood cells, the parasites can either replicate to form more merozoites, which continue to infect more red blood cells, or they can produce gametocytes. Gametocytes are taken up by insects that feed on the vertebrate host. In the insect host, the gametocytes merge to sexually reproduce. After sexual reproduction, the parasites develop into new sporozoites, which then migrate to the insect’s salivary glands.

When the insect bites a vertebrate host, the sporozoites are injected into the host’s blood, continuing the cycle. This complex life cycle ensures the survival and transmission of the Plasmodium species between hosts.

Anti-HAV IgM antibodies are diagnostic. Disease in children is more commonly asymptomatic, risk of symptomatic disease increases with age. Transmission is by the faecal-oral route. Faecal shedding has been demonstrated for 2 – 3 weeks before and about a week after, the onset of jaundice. Infection confers lifelong immunity.

The 22-year-old female likely developed a vaginal yeast infection caused by Candida albicans. This is a common occurrence after taking antibiotics, as the medication can disrupt the normal balance of bacteria and yeast in the body. Candida albicans is a type of fungus that is normally present in the vagina in small amounts. However, when the balance is disrupted, it can overgrow and lead to symptoms such as a whitish discharge.

Chlamydia, Trichomonas, Gardnerella, and Neisseria Gonorrhoeae are all sexually transmitted infections that can cause vaginal discharge, but they are less likely in this case given the recent dental procedure and antibiotic use. Candida is the most likely culprit in this scenario.

Treatment for a vaginal yeast infection typically involves antifungal medications, either in the form of creams or oral tablets. It is important for the patient to follow up with their healthcare provider for proper diagnosis and treatment.

The patient in this case is a 64-year-old woman with ankylosing spondylitis who presents with cough, weight loss, and tiredness. Her chest x-ray shows longstanding upper lobe fibrosis, and three sputum tests stain positive for acid fast bacilli (AFB) but are consistently negative for Mycobacterium tuberculosis on culture.

The most likely causative agent in this case is Mycobacterium avium intracellulare complex (MAC). Pulmonary MAC infection in immunocompetent hosts typically presents with symptoms such as cough, sputum production, weight loss, fever, lethargy, and night sweats. The onset of symptoms is usually insidious.

In patients suspected of having pulmonary MAC infection, diagnostic testing includes AFB staining and culture of sputum specimens. The ATS/IDSA guidelines provide criteria for establishing a diagnosis of nontuberculous mycobacterial lung disease, which includes clinical, radiographic, and bacteriologic criteria.

Clinical criteria for pulmonary MAC infection include pulmonary signs and symptoms such as cough, fatigue, weight loss, and dyspnea, as well as the appropriate exclusion of other diseases like carcinoma and tuberculosis. Sputum AFB stains are typically positive for MAC in patients with pulmonary MAC infection, and mycobacterial cultures can confirm the presence of MAC in about 1-2 weeks.

The most likely diagnosis for the 21-year-old man with general malaise, low-grade temperature, and painful ulceration of his mouth and gums is a Herpes simplex virus infection. This is indicated by the presence of gingivostomatitis, which is a characteristic feature of primary herpes simplex virus infection.

Herpetic gingivostomatitis is often the initial presentation during the first herpes simplex infection and is typically caused by HSV-1. It is more severe than herpes labialis (cold sores) and is the most common viral infection of the mouth. Symptoms of herpetic gingivostomatitis can include fever, anorexia, irritability, malaise, headache, submandibular lymphadenopathy, halitosis, and refusal to drink.

Other options such as Epstein Barr virus, Lichen planus, and HIV seroconversion illness are less likely in this case based on the presentation of symptoms. Epstein Barr virus infection may present with symptoms similar to infectious mononucleosis, Lichen planus typically presents with white, lacy patches in the mouth, and HIV seroconversion illness may present with a variety of symptoms but typically not with the characteristic ulceration seen in herpes simplex virus infection.

Primary syphilis is the initial stage of syphilis infection and is characterized by the presence of a painless, firm, ulcerated lesion known as a chancre. This lesion is typically found on the genitals, including the cervix in women, and is caused by the bacterium Treponema pallidum.

In this case, the lady was found to have a 12mm ulcerated, indurated lesion on her cervix during a speculum examination. Since she was otherwise asymptomatic and the lesion was painless, the most likely cause would be Treponema pallidum, the organism responsible for syphilis.

Other options such as Herpes Simplex Type 1 and Type 2, Neisseria gonorrhoeae, and Chlamydia Trachomatis D-K are not typically associated with the development of a painless ulcerated lesion like the one described in the scenario. Therefore, the most appropriate answer is Treponema pallidum.