Nausea and vomiting (due to gastroenteritis) - Symptoms, Causes, Treatment & Prevention

Overview

Gastroenteritis, often called “stomach flu,” is an inflammation of the stomach and intestines caused by infectious agents (viruses, bacteria, parasites) or, less commonly, by toxins and medications. The hallmark manifestations are nausea and vomiting, which result from irritation of the gastrointestinal (GI) lining and the brain’s vomiting center.

Anyone can develop gastroenteritis, but certain groups—young children, older adults, and people with weakened immune systems—are more likely to experience severe symptoms and dehydration.

According to the U.S. Centers for Disease Control and Prevention (CDC), there are roughly 48 million cases of food‑borne gastroenteritis each year in the United States, leading to 128,000 hospitalizations and about 3,000 deaths. Worldwide, the World Health Organization (WHO) estimates that diarrheal diseases (most often caused by gastroenteritis) account for 1.7 million deaths annually, especially in low‑resource settings.

Symptoms

The clinical picture varies with the underlying pathogen, but the following symptoms are frequently seen together with nausea and vomiting:

• Nausea – An uneasy sensation in the stomach often preceding vomiting.
• Vomiting – Forceful expulsion of stomach contents; may be non‑bilious or contain bile (green‑yellow).
• Diarrhea – Watery, often urgent stools; may be bloody with certain bacterial infections.
• Abdominal cramps – Intermittent or constant pain, usually crampy.
• Fever – Low‑grade (≤38.5 °C) in viral cases; higher fevers suggest bacterial infection.
• Headache & muscle aches – Common with viral agents (e.g., norovirus, rotavirus).
• Loss of appetite – Due to nausea and GI upset.
• Dehydration signs – Dry mouth, decreased urine output, dizziness, sunken eyes, or rapid heart rate.
• General malaise – Feeling weak or fatigued.

Symptoms typically begin 6–48 hours after exposure and last 1–3 days for viral causes; bacterial infections may persist longer (up to 7–10 days) if untreated.

Causes and Risk Factors

Infectious agents

• Viruses – Norovirus (most common in adults), rotavirus (leading cause in children), adenovirus, astrovirus.
• Bacteria – Salmonella, Campylobacter, Escherichia coli (especially O157:H7), Shigella, Vibrio cholerae.
• Parasites – Giardia lamblia, Cryptosporidium, Entamoeba histolytica.

Non‑infectious triggers

• Food‑borne toxins (e.g., scombroid poisoning, mushroom toxins).
• Medication side‑effects (chemotherapy, opioids, antibiotics like clindamycin).
• Travel‑related “traveler’s diarrhea” – often bacterial.

Risk factors

• Age < 5 years or > 65 years.
• Immunocompromised state (HIV, chemotherapy, transplant recipients).
• Living in crowded or unsanitary conditions.
• Recent consumption of raw/undercooked foods, unpasteurized dairy, or contaminated water.
• Close contact with an infected person (family, daycare, nursing home).

Diagnosis

Most cases of viral gastroenteritis are diagnosed clinically based on history and physical exam. However, when the presentation is severe, atypical, or suggests bacterial infection, further testing is warranted.

Clinical assessment

• Detailed history – onset, duration, food exposures, travel, sick contacts, medication use.
• Physical exam – abdominal tenderness, hydration status, fever, signs of systemic illness.

Laboratory tests

• Stool culture & PCR panel – Identifies bacterial or viral pathogens; recommended if diarrhea is bloody, high fever, or lasts > 3 days.
• Stool ova & parasite exam – Used when travel to endemic areas or prolonged symptoms (> 1 week).
• Complete blood count (CBC) – Looks for leukocytosis (bacterial infection) or anemia (possible blood loss).
• Electrolytes, BUN/Creatinine – Assess dehydration and renal function.
• Serologic tests – E.g., for