African swine fever: symptoms, spread, control, and vaccine status

TL;DR:

ASF is a deadly pig virus, not a human health risk.
It spreads via pigs, pork, people, vehicles, and soft ticks.
No cure. Control relies on strong on-farm biosecurity.
As of 2025, Vietnam uses domestic ASF vaccines with limits.
Report suspect cases fast. Quick action saves herds and trade.

African swine fever: a clear guide for farmers, vets, and travelers

African swine fever, or ASF, is a severe viral disease in pigs. It hits domestic pigs and wild boar. It does not infect people or make pork unsafe to eat. Mortality can reach 100 percent in naive herds. As of October 6, 2025, ASF remains one of the top threats to global pork. FAO and WOAH describe ASF as highly contagious with heavy farm and trade impacts.

What is ASF and why it persists

ASF is caused by a large DNA virus, African swine fever virus. The virus belongs to the Asfarviridae family. It can persist in pork products, carcasses, and the environment. In Africa, a sylvatic cycle involves warthogs and soft ticks, which helps the virus endure in nature.

The disease saw renewed global spread after 2007. It moved across parts of Europe and Asia. In 2023, EFSA reported ASF in 14 EU member states, with wild boar outbreaks rising from 2022. This shows how hard it is to stop once established.

Can people get ASF or spread it?

People do not get sick from ASF. Pork is safe if inspected and cooked as usual. The risk comes from people moving the virus between sites. Contaminated boots, tools, trucks, and feed can carry the virus. Bringing pork or sausages from affected regions is a known risk.

Soft ticks of the genus Ornithodoros can spread ASF in some settings. This vector adds complexity in endemic zones. Most spread worldwide still comes from infected pigs, pork, and fomites.

What to watch for in pigs

Signs vary by strain and dose, but common red flags include:

High fever, loss of appetite, weakness.
Red or cyanotic skin patches, especially on ears, abdomen, and legs.
Vomiting or diarrhea with blood.
Sudden deaths with few signs, especially in young pigs.

Any sudden spike in death or fever should trigger an immediate vet call. Quick reporting limits spread and reduces losses. National programs, such as USDA APHIS, stress early detection and strict movement control.
How ASF spreads on and between farms

ASF spreads through direct contact with infected pigs and fluids. It also spreads via carcasses, transport, swill feeding, and dirty equipment. The virus survives for long periods in chilled or cured meat. Hunters and farm visitors can carry it on clothing or gear if they skip cleaning. EFSA and FAO both warn about the role of wild boar in Europe and Asia.

The travel link

Travelers who bring home pork from affected regions can seed new outbreaks. Many countries ban personal pork imports from ASF areas. Always check local rules before travel. Dispose of food waste safely so pigs and wild boar cannot reach it.

No cure, and vaccine status in 2025

There is no treatment once pigs are infected. Control relies on rapid culling in outbreaks and strict biosecurity at all times. Historically there has been no safe, widely available vaccine. In 2023, Vietnam approved domestic vaccines and began limited rollouts. In 2025, Reuters reported low uptake and ongoing outbreaks, showing limits to current tools and the continued need for biosecurity. Global authorities still frame vaccination as only one layer, not a replacement for core controls.

Practical biosecurity that works

The goal is to keep the virus off your farm, and if detected, to stop it leaving.

Entry controls

Limit farm access to essential people only.
Keep a visitor log with recent farm contact history.
Provide farm-only boots and coveralls at the gate.

Clean movement

Wash and disinfect trucks, trailers, and tools on entry and exit.
Use clear clean-dirty lines at barns.
Set up hand wash and boot dips at all doors.

Feed and pork risks

Do not feed swill or kitchen waste containing meat.
Source feed ingredients from trusted suppliers.
Store feed to block contact with wild boar and feral swine.

Pig and carcass management

Quarantine all incoming pigs for at least 30 days.
Remove and secure dead stock fast, then clean and disinfect.
Fence to reduce contact with wild boar where they are present.

People and hunting

Separate hunting gear from farm gear.
After hunting, wash, change clothes, and disinfect boots before visiting pigs.
Do not bring wild boar meat to pig sites.

Quick reference checklist

Area	Do this every day	Who checks	Done
Gate	Log visitors, hand out farm boots and suits	Staff on duty	☐
Vehicles	Wash wheels and undercarriage, spray disinfectant	Yard crew	☐
Barn doors	Keep footbath fresh, post wash rules	Barn lead	☐
Pigs	Isolate sick pigs, call vet on fever clusters	Herd tech	☐
Dead stock	Remove within hours, secure bin, clean site	Yard crew	☐
Feed	Seal bins, block wildlife access	Feed manager	☐

You can print this table and use it as a daily form.

What happens during an outbreak

Authorities set control zones and restrict pig and product movements. They trace contacts between farms and transporters. Cleaning, disinfection, and fallow periods follow culling. In the United States, APHIS publishes emergency response guides and training for state partners and producers. Similar playbooks exist in many countries.

Wild boar and landscape risk

In much of Europe, wild boar sustain ASF outside farms. Hunters, foresters, and hikers help by reporting carcasses and avoiding carcass handling. Fencing and carcass removal programs cut risk around pig-dense regions. EFSA’s 2024 review documented more wild boar outbreaks in 2023 than 2022, reflecting ongoing pressure at the wildlife-livestock interface.

Communication and staff training

Farm teams need short, clear rules and drills. Use toolboxes, posters, and short videos. Programs like USDA’s Protect Our Pigs offer ready-to-use guides, signs, and training clips. Adapt the materials to your layout and language.

Common mistakes to avoid

Allowing visitors in street shoes, even for a minute.
Skipping truck wash because it rained.
Buying pigs without a quarantine pen.
Keeping the same set of tools for the whole site.
Letting food scraps near pig areas or manure pits.

When to call and what to report

Call your vet or the national animal health hotline at the first hint of unusual deaths or high fevers. Share dates, number of pigs, signs, and recent movements. Report any dead feral swine with no clear cause. In the U.S., USDA Wildlife Services takes such reports.

Why it matters

ASF kills pigs and erodes farmer income. It hits national pork supply, raises prices, and strains food security. Fast detection and daily biosecurity are the best defenses. Vaccines may help in some places, but they do not replace basic controls.

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