Diseases beginning with H
U.S.-focused summaries with current official guidance links. For a diagnosis, personal vaccine schedule, pregnancy advice, or urgent symptoms, speak with a qualified clinician.
Hepatitis A
Routine/risk-based vaccineDisease
A contagious liver infection caused by hepatitis A virus, usually spread through contaminated food, water, hands, or close contact.
Symptoms
Fatigue, nausea, stomach pain, loss of appetite, fever, dark urine, pale stool, or yellow skin and eyes; young children may have none.
Typical duration
Symptoms usually last under two months, though some people are ill for up to six months.
How serious is it?
Most recover completely, but rare liver failure can occur, particularly in older adults or people with chronic liver disease.
Treatment & management
No specific antiviral treatment; care focuses on rest, nutrition, fluids, and medical monitoring.
Vaccine: who and when?
Products: Havrix and Vaqta, usually given as a two-dose series beginning at 12-23 months, with catch-up and risk- or travel-based vaccination for others. Twinrix combines hepatitis A and B for adults and normally uses a three-dose series, with an accelerated option requiring a later booster.
Hepatitis B
Routine/risk-based vaccineDisease
A liver infection caused by hepatitis B virus and spread through blood and certain body fluids.
Symptoms
Many have no symptoms; possible fatigue, nausea, stomach pain, dark urine, joint pain, or jaundice.
Typical duration
Acute illness may last weeks; infection can become chronic and persist for life.
How serious is it?
Chronic infection can cause cirrhosis, liver failure, and liver cancer.
Treatment & management
Acute infection is usually monitored and supported; chronic hepatitis B may need long-term antiviral treatment and liver surveillance.
Vaccine: who and when?
Products include Engerix-B and Recombivax HB, commonly used in three-dose schedules, and Heplisav-B, a two-dose adult series. Twinrix combines hepatitis A and B. Newborns need a birth dose, while later dosing depends on age, product, immune status, and risk.
Hib Disease
Routine childhood vaccineDisease
Illness caused by Haemophilus influenzae type b bacteria, including meningitis, pneumonia, and bloodstream infection.
Symptoms
Depend on the infection and may include fever, stiff neck, severe headache, confusion, breathing difficulty, or extreme sleepiness.
Typical duration
Can progress quickly; recovery varies with the infection and how early treatment begins.
How serious is it?
Invasive Hib is a medical emergency and can cause brain damage, hearing loss, or death.
Treatment & management
Hospital antibiotics are needed for invasive disease; close contacts sometimes need preventive antibiotics.
Vaccine: who and when?
Products: ActHIB and Hiberix in four-dose schedules, and PedvaxHIB in a three-dose schedule. Hib protection is also included in Pentacel and Vaxelis. Infants usually start at 2 months; product and risk determine the remaining doses.
Human Papillomavirus (HPV)
Routine vaccineDisease
A very common group of viruses; persistent high-risk HPV can cause several cancers.
Symptoms
Most infections cause no symptoms. Some types cause genital warts; precancer and cancer may develop years later.
Typical duration
Most infections clear within one to two years, but persistent infection can last longer.
How serious is it?
Can cause cervical, anal, penile, vaginal, vulvar, and throat cancers.
Treatment & management
There is no treatment for the virus itself; clinicians treat warts, precancers, or cancers. Screening remains important where recommended.
Vaccine: who and when?
Product: Gardasil 9. Routine vaccination is recommended at ages 11-12 and may begin at 9. Two doses are used when the series starts before age 15; three doses are used for later starts or certain immunocompromising conditions. Catch-up is recommended through 26, with shared decision-making at ages 27-45.
Check the current CDC guidance for Human Papillomavirus (HPV) →
Last reviewed against official U.S. sources: September 5, 2026. This page provides general education, not medical advice.