Young Britons planning charity work in developing countries have an "ethical responsibility" to consider whether to cancel travel plans during the swine flu pandemic.
Professor Robert Dingwall, an adviser to the Department of Health, said: "While travel bans may not be justifiable, UK travellers cannot avoid thinking about their personal ethical responsibilities to the people of the countries that they are visiting.
"Staying at home this year will often be the morally right thing to do."
He added that there were not enough anti-viral drugs to treat more than about 5% of the world's population, and developing countries, such as those in sub-Saharan Africa, had virtually none of the stock in public hands and were already facing a "huge challenge" in treating people already sick with HIV/AIDS.
But John McEwan, chairman of the Association of British Travel Agents (ABTA), urged people to continue to travel, stressing that the World Health Organization did not support travel restrictions.