Backpackers Guide to Waterborne Viruses

When backpacking, hiking or camping in remote areas, access to safe drinking water is essential. Although streams, rivers and lakes may appear clean, they can contain harmful microorganisms, including viruses that cause gastrointestinal illness.

Waterborne viruses can enter natural water sources through human waste, sewage contamination and poor sanitation. Because viruses are microscopic, their presence cannot be identified by looking at, smelling or tasting the water.

Unlike many bacteria and protozoan parasites, viruses are small enough to pass through numerous standard backpacking water filters. Understanding this limitation is particularly important when travelling in areas where human sewage contamination may be a concern.

This guide explains five viruses that can spread through contaminated water, their potential health effects and the precautions backpackers can take to reduce the risk of infection.

How Do Waterborne Viruses Spread?

Many waterborne viruses spread through the faecal-oral route. This occurs when microscopic traces of infected faecal matter enter the mouth, often through contaminated drinking water, food, hands or surfaces.

Potential sources of contamination include:

• Untreated sewage entering rivers, lakes or streams.
• Inadequate sanitation around campsites and popular outdoor areas.
• Floodwater carrying sewage and other waste into natural water sources.
• Contaminated hands, food preparation surfaces and drinking containers.
• Water collected downstream of settlements or poorly maintained sanitation systems.

Even clear, fast-flowing water can contain viruses. Choosing the cleanest available source and using an appropriate treatment method are both important.

For advice on identifying potential collection points, read our guide to natural sources of drinking water when backpacking.

1. Norovirus

Norovirus is a highly contagious virus and a common cause of acute gastroenteritis. It spreads readily between people and can also be transmitted through contaminated water, food and surfaces.

Characteristics

• Virus Type: Non-enveloped, single-stranded RNA virus.
• Family: Caliciviridae.
• Approximate Size: 27–40 nanometres.

Transmission

Norovirus is primarily transmitted through the faecal-oral route, although particles released during vomiting can also contaminate nearby surfaces and food.

In outdoor environments, infection may result from drinking water contaminated by human waste or handling food and equipment with contaminated hands.

Symptoms

Symptoms generally begin 12–48 hours after exposure and may include:

• Sudden nausea and vomiting.
• Watery diarrhoea.
• Stomach cramps.
• Occasional fever, headache and muscle aches.

Most people recover within one to three days, although dehydration can become serious, particularly in young children, older adults and vulnerable individuals.

Prevention

• Use appropriately treated drinking water.
• Wash hands thoroughly with soap and water, especially after using the toilet and before preparing food.
• Keep food preparation areas and drinking equipment clean.
• Avoid preparing food for others while ill and for at least 48 hours after symptoms stop.

Important: Alcohol-based hand sanitiser is not a reliable substitute for washing with soap and water when preventing norovirus transmission.

Treatment

There is no specific antiviral treatment for most norovirus infections. Care generally focuses on replacing lost fluids and electrolytes and allowing time for recovery.

Seek medical advice if symptoms are severe, dehydration develops or fluids cannot be kept down.

2. Hepatitis A Virus (HAV)

Hepatitis A is a viral infection affecting the liver. Unlike the short-lived gastrointestinal illnesses caused by several other waterborne viruses, hepatitis A can cause symptoms lasting weeks or months.

It is more commonly associated with regions where sanitation and access to safe drinking water are inadequate.

Characteristics

• Virus Type: Single-stranded RNA virus.
• Family: Picornaviridae.
• Approximate Size: 27–32 nanometres.

Transmission

Hepatitis A spreads through the faecal-oral route, including consumption of contaminated food or water and close contact with an infected person.

Travellers visiting areas with inadequate sanitation may face an increased risk, particularly when drinking untreated water or eating food prepared under unhygienic conditions.

Symptoms

Symptoms may develop approximately 15–50 days after infection and can include:

• Fatigue and fever.
• Nausea, vomiting and abdominal discomfort.
• Loss of appetite.
• Dark urine and pale stools.
• Jaundice, causing yellowing of the skin or whites of the eyes.

Some infected individuals, particularly young children, may experience few or no symptoms.

Prevention

• Consider hepatitis A vaccination before travelling to destinations where it is recommended.
• Use safe drinking water and follow good food hygiene practices.
• Wash hands thoroughly after using the toilet and before eating.
• Avoid food and drinks that may have been prepared with contaminated water.

UK travellers should check current destination-specific advice through the TravelHealthPro website or a qualified travel health professional.

Treatment

There is no specific antiviral treatment for hepatitis A. Medical care focuses on monitoring liver function, managing symptoms and supporting recovery.

Anyone who develops jaundice or suspects hepatitis A should seek prompt medical assessment.

3. Rotavirus

Rotavirus is a cause of gastroenteritis, particularly among infants and young children. Vaccination programmes have substantially reduced severe rotavirus illness in countries where routine childhood vaccination is available.

Characteristics

• Virus Type: Double-stranded RNA virus.
• Family: Sedoreoviridae.
• Approximate Size: 70–75 nanometres.

Transmission

Rotavirus spreads mainly through the faecal-oral route and can contaminate hands, surfaces, food and water.

Although children are most commonly affected, adults can also become infected.

Symptoms

Symptoms typically develop around two days after exposure and may include:

• Watery diarrhoea.
• Vomiting.
• Fever.
• Abdominal pain.
• Dehydration resulting from fluid loss.

Illness commonly lasts three to eight days.

Prevention

• Follow recommended childhood vaccination schedules.
• Use appropriately treated drinking water.
• Wash hands with soap and water and maintain good sanitation.
• Clean contaminated surfaces and shared equipment.

Treatment

Treatment focuses on preventing and managing dehydration, often using oral rehydration solutions.

Severe dehydration may require urgent medical treatment, particularly in infants and young children.

4. Adenovirus

Adenoviruses are a group of viruses capable of causing several types of illness, including respiratory infections, conjunctivitis and gastroenteritis.

Some adenovirus types are associated with gastrointestinal illness, while others primarily affect the respiratory system or eyes.

Characteristics

• Virus Type: Non-enveloped, double-stranded DNA virus.
• Family: Adenoviridae.
• Approximate Size: 70–90 nanometres.

Transmission

Adenoviruses can spread through respiratory secretions, close contact, contaminated surfaces and, in some cases, the faecal-oral route.

Exposure to contaminated recreational water is another recognised transmission route for certain adenoviruses.

Symptoms

Symptoms depend on the adenovirus type and may include:

• Diarrhoea, vomiting and abdominal discomfort.
• Fever.
• Sore throat, cough and other respiratory symptoms.
• Conjunctivitis, sometimes called pink eye.

The incubation period and duration of illness vary according to the type of infection.

Prevention

• Use properly treated drinking water.
• Wash hands regularly and avoid sharing contaminated personal items.
• Maintain good hygiene around communal cooking and washing areas.
• Avoid swimming in water suspected of sewage contamination.

Treatment

Most adenovirus infections are managed with supportive care, including rest and adequate fluid intake.

People with severe symptoms, breathing difficulties or weakened immune systems should seek medical advice promptly.

5. Astrovirus

Astroviruses are associated with gastroenteritis, particularly in young children, older adults and people with weakened immune systems.

Illness is often relatively mild in otherwise healthy individuals, although more serious infections can occur in vulnerable people.

Characteristics

• Virus Type: Non-enveloped, single-stranded RNA virus.
• Family: Astroviridae.
• Approximate Size: 28–35 nanometres.

Transmission

Astroviruses spread primarily through the faecal-oral route. Contaminated water, food, hands and surfaces can contribute to transmission.

Symptoms

Symptoms may include:

• Watery diarrhoea.
• Nausea or vomiting.
• Abdominal discomfort.
• Occasional low-grade fever.

Symptoms often develop within a few days of exposure and usually resolve within several days, although the course of illness can vary.

Prevention

• Use appropriately treated drinking water.
• Wash hands thoroughly before eating and after using the toilet.
• Maintain clean food preparation equipment and surfaces.
• Avoid sharing drinking containers with anyone experiencing gastrointestinal illness.

Treatment

There is no specific treatment for routine astrovirus gastroenteritis. Care generally focuses on maintaining hydration and replacing lost electrolytes.

Medical advice should be sought if symptoms become severe or dehydration develops.

How to Remove or Inactivate Viruses in Drinking Water

One of the most important considerations for backpackers is choosing a water treatment method that provides protection against viruses.

Not all portable filtration systems offer this protection.

Boiling

Boiling is an effective method of inactivating waterborne viruses, bacteria and protozoan parasites.

Bring water to a full rolling boil for at least one minute. At elevations above approximately 2,000 metres, boil for three minutes.

Allow the water to cool before drinking and store it in a clean container to prevent recontamination.

Boiling does not reliably remove chemical pollutants or heavy metals.

Portable Water Filters

Many standard backpacking filters use hollow-fibre membranes or other filtration media designed to remove bacteria and protozoa.

However, viruses are much smaller than these microorganisms, and most standard backpacking microfilters do not reliably remove viruses.

Some specialist water purifiers use additional filtration technologies or treatment stages that can provide virus protection. Always check the manufacturer's independently supported performance claims.

Explore our portable water filters.

Chemical Water Treatment

Suitable chemical disinfectants can inactivate many waterborne viruses when used correctly.

Chlorine dioxide products are commonly used by backpackers because they are compact and lightweight. However, the correct dosage and contact time are essential.

Treatment effectiveness depends on the product, water temperature, clarity and microorganisms present. Some protozoan parasites require substantially longer treatment times than viruses.

Always follow the manufacturer's instructions rather than relying on a general treatment time.

Browse our chemical water purification products.

Ultraviolet (UV) Treatment

Portable UV purifiers can inactivate viruses and other microorganisms when operated correctly.

UV treatment works best in clear water because suspended particles can prevent the light from reaching microorganisms.

UV devices also require a reliable power source and do not remove sediment or chemical contaminants.

Combining Treatment Methods

Where virus contamination is a concern, a suitable combination of filtration and disinfection may provide broader protection than a standard microfilter alone.

For example, filtration may remove bacteria and protozoa while a compatible disinfectant provides additional protection against viruses.

Follow the instructions for both products, including the correct order of treatment.

For a detailed comparison of methods, read our Guide to Drinking Water Treatments When on Adventures.

Preventing Waterborne Illness While Backpacking

Water treatment is only one part of preventing infection. Good hygiene and sensible campsite practices are equally important.

• Choose Water Sources Carefully: Avoid collecting water downstream of obvious sewage contamination, heavily used campsites or other pollution sources.
• Wash Your Hands: Use soap and safe water after using the toilet and before preparing or eating food.
• Keep Clean and Dirty Water Separate: Avoid transferring untreated water onto clean bottle openings, caps or drinking equipment.
• Dispose of Human Waste Responsibly: Use toilets where available and follow local guidance for waste disposal when camping in remote areas.
• Clean Cooking Equipment: Use appropriately treated water for washing utensils and food preparation surfaces where necessary.
• Avoid Sharing Drinking Equipment: Particularly when someone in the group has symptoms of gastrointestinal illness.
• Carry a Backup Treatment Method: Equipment failures, flat batteries and unexpected water conditions can disrupt your planned treatment method.
• Check Travel Health Advice: Vaccinations and additional precautions may be recommended for particular destinations.

What to Do If You Become Ill While Backpacking

Vomiting and diarrhoea can cause dehydration, especially during strenuous activity or in hot conditions.

If you develop gastrointestinal symptoms:

• Stop strenuous activity and rest where possible.
• Drink safe water regularly and consider oral rehydration salts to replace lost fluids and electrolytes.
• Monitor for signs of dehydration, including reduced urination, dizziness and unusual weakness.
• Avoid preparing food for other people while experiencing vomiting or diarrhoea.
• Seek medical advice if symptoms persist, worsen or are accompanied by significant abdominal pain or fever.

Seek urgent medical assistance if you develop severe dehydration, confusion, fainting, bloody diarrhoea, an inability to keep fluids down or symptoms of serious illness.

Yellowing of the skin or eyes may indicate a liver problem and requires prompt medical assessment.

When travelling in remote areas, consider how you would obtain assistance if illness prevents you from continuing your journey.

Conclusion: Protecting Yourself Against Waterborne Viruses

Waterborne viruses are an important consideration when collecting drinking water from natural sources, particularly in areas where human waste or inadequate sanitation may affect water quality.

Norovirus, hepatitis A, rotavirus, adenovirus and astrovirus can all cause illness, although their transmission routes, symptoms and severity vary.

For backpackers, the most important precautions are to choose water sources carefully, use a treatment method suitable for the likely contamination risks and maintain good hygiene throughout the trip.

Remember that standard portable water filters do not necessarily provide protection against viruses. Where virus contamination is a concern, consider an appropriate disinfection method or a specialist purifier with verified virus protection.

To prepare for your next adventure, explore our water filters and chemical water purification products.