Do birds carry harmful diseases?

Q. I am having a dispute with a friend of mine who insists that birds do not carry any diseases harmful to humans. All of the scientific data that I have read say exactly the opposite, and respected researchers state that birds and their droppings are a source of diseases, many of them extremely deleterious to humans.

Could you please shed some light on this subject? Many thanks!

Leonard K.

A. You are right: It’s true that birds can transmit diseases harmful to humans. There are about 60 diseases worldwide spread by different species of birds. Examples include the infamous avian flu; histoplasmosis, a respiratory disease which is caused by a fungus that grows when heaps of bird droppings accumulate; and cryptococcosis, another disease spread by fungal spores that grow on bird droppings.

Most diseases spread to humans by birds are relatively rare and easily treated. A particular strain of avian flu was an exception. An outbreak of the dangerous H5N1 virus in Southeast Asia, which began in 2003, was especially worrisome; the disease spread to 650 people in 15 countries (not including the United States), and was fatal in 60 percent of the cases. How did it spread from the birds? One 18-year-old man, who died of the disease in 2005, kept fighting cocks, and bet heavily on them. To keep his roosters alive so they could continue fighting, he would suck blood and mucus from their beaks and send the birds back into the ring. Other people who died of the disease consumed a popular regional concoction made from raw duck’s blood. No wonder the people got sick!

It’s important to remember that the diseases carried by all 10,000 species of birds on the Earth harm far fewer people than the germs carried by humans. People spread thousands of diseases — what we call “the common cold” is really 200 different viruses. Humans are the disease vectors to worry about — as those of us who travel on planes, work in offices, or have a child in day care can easily attest. The chance of a given bird giving you a disease are very slim indeed. If you can refrain from sucking mucus from roosters’ beaks, drinking raw duck blood, and handling a lot of bird droppings, you will probably be just fine.

Q. In response to Sy’s Valentine article on octopus sex, one reader wrote via Twitter: “More articles on romance from the deep, please!”

A. We are happy to oblige. The octopus, despite its bendy, boneless body and hundreds of questing suckers, is an almost staid lover compared with my favorite sea slug. A particularly sexy species known as Chromodoris reticulata inhabits shallow coral reefs around Japan. All have both male and female sex organs — and can use them both at the same time! The male organ of each fits into the female opening of the other. The lovemaking is apparently so intense that the male organs actually fall off. But no matter; happily, the lovers can grow them back in a few days — and go at it all over again.

You would probably love a new book, “Sex in the Sea,” by reef ecologist Marah Hardt. She writes about giant whale testicles (the biggest on the planet), orgies among silvery fish named grunions and stationary corals, and the remarkably tender attentions of crustaceans we normally consider rather crusty: lobsters. After a courtship that involves claw tapping and a lot of urination, the female sheds her hard exoskeleton. While she’s in this vulnerable state, her mate steps up like a real gentleman. He “gently picks her up in his legs,” Hardt told National Geographic News Service, “cradles her, and rolls her onto her back. . .” They then consummate their relationship in the missionary position.